Licar/renderer.h

/**
  3D renderer: implements 3D rendering.
*/

#ifndef _LCR_RENDERER_H
#define _LCR_RENDERER_H

#define S3L_RESOLUTION_X LCR_SETTING_RESOLUTION_X
#define S3L_RESOLUTION_Y LCR_SETTING_RESOLUTION_Y
#define S3L_PIXEL_FUNCTION _LCR_pixelFunc3D
#define S3L_PERSPECTIVE_CORRECTION 2
#define S3L_NEAR_CROSS_STRATEGY 1
#define S3L_Z_BUFFER 1

#include "small3dlib.h"

/// Renderer specific unit, length of one map square.
#define LCR_RENDERER_UNIT (S3L_F / 2)
  // NOTE: ^ S3L_F sometimes makes some triangles bug, S3L_F/2 seems to fix it
  // but it's more jerky, maybe try to apply anti-overflow in S3L?

#define LCR_RENDERER_CHUNK_RESOLUTION 4 // do not change
#define LCR_RENDERER_LOD_BLOCKS 64      // do not change

#define LCR_RENDERER_CHUNK_SIZE_HORIZONTAL \
  ((LCR_MAP_SIZE_BLOCKS * LCR_RENDERER_UNIT) / LCR_RENDERER_CHUNK_RESOLUTION)

#define LCR_RENDERER_CHUNKS_TOTAL (LCR_RENDERER_CHUNK_RESOLUTION * \
  LCR_RENDERER_CHUNK_RESOLUTION * LCR_RENDERER_CHUNK_RESOLUTION)

#define LCR_RENDERER_MODEL_COUNT 10
#define LCR_RENDERER_CAR_SCALE (LCR_RENDERER_UNIT / 4)

/** For some reason the map model is a bit misaligned with physics world, this
  kinda hotfixes it -- later try to discover source of this bug. TODO */
#define _LCR_MAP_MODEL_SCALE 1034

#define LCR_RENDERER_MAT_CP0 0x0f ///< material for untaken checkpoint
#define LCR_RENDERER_MAT_CP1 0x0e
#define LCR_RENDERER_MAT_FIN 0x0d

struct
{
  S3L_Scene scene;
  S3L_Model3D mapModel; ///< whole map model
  S3L_Model3D *carModel;
  S3L_Model3D *ghostModel;

  /**
    The scene model array.
    0, 1, 2, 3, 4, 5, 6, 7: nearest map chunk models
    8:                      car model
    9:                      ghost model
  */
  S3L_Model3D models[LCR_RENDERER_MODEL_COUNT];

  uint32_t frame;

  uint8_t loadedChunks[8]; ///< numbers of loaded map chunks

  S3L_Unit mapVerts[LCR_SETTING_MAX_MAP_VERTICES * 3];
  S3L_Index mapTris[LCR_SETTING_MAX_MAP_TRIANGLES * 3];

  S3L_Index chunkStarts[LCR_RENDERER_CHUNKS_TOTAL];

  /**
    Additional data for triangles. 4 higher bits hold direction (for lighting):
    0 is floor, 1 is wall, 2 is wall (90 degrees). 4 lower bits hold the
    texture index.
  */
  uint8_t mapTriangleData[LCR_SETTING_MAX_MAP_TRIANGLES];

  /**
    8x8x8 3D grid of bits, each bit says (for each corresponding part of map)
    whether there is an LOD block or not.
  */
  uint8_t gridOfLODs[LCR_RENDERER_LOD_BLOCKS];

#if LCR_ANIMATE_CAR
  S3L_Unit wheelRotation;
  S3L_Unit wheelSteer;
  S3L_Unit wheelRotationCenters[4]; /**< back and front wheel XY centers */
  S3L_Unit animatedCarVerts[LCR_CAR_VERTEX_COUNT * 3];
#endif

  // pixel function precomputed values:
  uint32_t previousTriID;
  int triUVs[6];
  int texSubsampleCount;
  unsigned int flatAndTransparent; /**< If non-zero, transparent (dithered)
                                        polygons will be drawn without texture,
                                        with color stored in this variable. */
} LCR_renderer;

void LCR_rendererSetCarTransform(LCR_GameUnit position[3],
  LCR_GameUnit rotation[3])
{
  LCR_LOG2("setting car transform");

  LCR_renderer.carModel->transform.translation.x =
    (position[0] * LCR_RENDERER_UNIT) / LCR_GAME_UNIT;
  LCR_renderer.carModel->transform.translation.y =
    (position[1] * LCR_RENDERER_UNIT) / LCR_GAME_UNIT;
  LCR_renderer.carModel->transform.translation.z =
    (position[2] * LCR_RENDERER_UNIT) / LCR_GAME_UNIT;

  LCR_renderer.carModel->transform.rotation.x = S3L_wrap((rotation[0] *
    S3L_F) / LCR_GAME_UNIT,S3L_F);
  LCR_renderer.carModel->transform.rotation.y = S3L_wrap((rotation[1] *
    S3L_F) / LCR_GAME_UNIT,S3L_F);
  LCR_renderer.carModel->transform.rotation.z = S3L_wrap((rotation[2] *
    S3L_F) / LCR_GAME_UNIT,S3L_F);
}

void _LCR_pixelFunc3D(S3L_PixelInfo *pixel)
{
  // once we get a new triangle, we precompute things for it:
  if (pixel->triangleID != LCR_renderer.previousTriID)
  {
    LCR_renderer.previousTriID = pixel->triangleID;
    LCR_renderer.flatAndTransparent = 0;

#if LCR_SETTING_TEXTURE_SUBSAMPLE != 0
    LCR_renderer.texSubsampleCount = 0;
#endif

    if (pixel->modelIndex == 9)
    {
      // car ghost model
      LCR_renderer.flatAndTransparent = LCR_SETTING_GHOST_COLOR;
    }
    else if (pixel->modelIndex == 8)
    {
      // car model
      LCR_loadImage(LCR_IMAGE_CAR);

      for (int i = 0; i < 6; ++i)
      {
        LCR_renderer.triUVs[i] =
          (LCR_carUvs[2 * LCR_carTriangleUvs[
            3 * pixel->triangleIndex + i / 2] + i % 2] * (LCR_IMAGE_SIZE + 1))
            / 512;
      }
    }
    else
    {
      // map model
      const S3L_Index *t = 
        LCR_renderer.models[pixel->modelIndex].triangles +
          3 * pixel->triangleIndex;
      S3L_Unit *v[3];

      for (int i = 0; i < 3; ++i)
        v[i] = LCR_renderer.mapVerts + 3 * t[i];

      const uint8_t *triData =
        LCR_renderer.mapTriangleData +
          LCR_renderer.chunkStarts[LCR_renderer.loadedChunks[
            pixel->modelIndex]];

      uint8_t type = triData[pixel->triangleIndex] >> 4;
      uint8_t mat = triData[pixel->triangleIndex] & 0x0f;

      switch (mat)
      {
#define CL (type ? 0x8210 : 0x0000)
        case LCR_RENDERER_MAT_CP0:
          LCR_renderer.flatAndTransparent = LCR_SETTING_CHECKPOINT_0_COLOR | CL;
          break;

        case LCR_RENDERER_MAT_CP1:
          LCR_renderer.flatAndTransparent = LCR_SETTING_CHECKPOINT_1_COLOR | CL;
          break;

        case LCR_RENDERER_MAT_FIN:
          LCR_renderer.flatAndTransparent = LCR_SETTING_FINISH_COLOR | CL;
#undef CL
          break;

        default:
          LCR_loadImage(mat);

          if (type == 0) // floor?
          {
            if (v[0][1] != v[1][1] || v[1][1] != v[2][1]) // angled floor?
              LCR_imageChangeBrightness(1);

            for (int i = 0; i < 6; ++i)
              LCR_renderer.triUVs[i] = ((
                (v[i / 2][(i % 2) * 2]) *
                  LCR_IMAGE_SIZE) / LCR_RENDERER_UNIT);
          }
          else
          {
            if (type == 1)
              LCR_imageChangeBrightness(0);

            for (int i = 0; i < 6; ++i)
            {
              LCR_renderer.triUVs[i] = ((
                (v[i / 2][i % 2 ? 1 : (type == 1 ? 2 : 0)]) *
                  LCR_IMAGE_SIZE) / LCR_RENDERER_UNIT);

              if (i % 2)
                LCR_renderer.triUVs[i] = LCR_IMAGE_SIZE -
                  LCR_renderer.triUVs[i];
            }
          }

          // shift the UVs to the origin (prevent high values of UV coords)
          for (int i = 0; i < 2; ++i)
          {
            uint8_t minCoord = LCR_renderer.triUVs[i] <
              LCR_renderer.triUVs[2 + i] ? (0 + i) : (2 + i);

            if (LCR_renderer.triUVs[4 + i] < LCR_renderer.triUVs[minCoord])
              minCoord = 4 + i;

            S3L_Unit shiftBy = LCR_renderer.triUVs[minCoord] % LCR_IMAGE_SIZE;

            if (shiftBy < 0)
              shiftBy += LCR_IMAGE_SIZE;

            shiftBy -= LCR_renderer.triUVs[minCoord];

            LCR_renderer.triUVs[i] += shiftBy;
            LCR_renderer.triUVs[2 + i] += shiftBy;
            LCR_renderer.triUVs[4 + i] += shiftBy;
          }
          break;
      }
    }
  }

  if (LCR_renderer.flatAndTransparent)
  {
    if (pixel->x % 2 == pixel->y % 2)
      LCR_drawPixelXYUnsafe(pixel->x,pixel->y,LCR_renderer.flatAndTransparent);
    else
      S3L_zBufferWrite(pixel->x,pixel->y,S3L_MAX_DEPTH);
      /* ^ Clear z-buffer if we don't draw the pixel. Without this further
      geometry drawn later on won't be seen through transparent objects which
      looks bad. With this "fix" glitches may still appear (wrong draw order)
      but it generally looks better this way. */

    return;
  }

  uint16_t color;

#if LCR_SETTING_TEXTURE_SUBSAMPLE != 0
  if (LCR_renderer.texSubsampleCount == 0)
  {
#endif
    int barycentric[3];

    barycentric[0] = pixel->barycentric[0] / 8;
    barycentric[1] = pixel->barycentric[1] / 8;
    barycentric[2] = pixel->barycentric[2] / 8;

    color = LCR_sampleImage(
      (barycentric[0] * LCR_renderer.triUVs[0] +
       barycentric[1] * LCR_renderer.triUVs[2] +
       barycentric[2] * LCR_renderer.triUVs[4])
       / (S3L_F / 8),
      (barycentric[0] * LCR_renderer.triUVs[1] +
       barycentric[1] * LCR_renderer.triUVs[3] +
       barycentric[2] * LCR_renderer.triUVs[5])
       / (S3L_F / 8));

#if LCR_SETTING_TEXTURE_SUBSAMPLE != 0
    LCR_renderer.texSubsampleCount = LCR_SETTING_TEXTURE_SUBSAMPLE;
  }

  LCR_renderer.texSubsampleCount--;
#endif

  LCR_drawPixelXYUnsafe(pixel->x,pixel->y,color);
}

S3L_Index _LCR_rendererAddMapVert(S3L_Unit x, S3L_Unit y, S3L_Unit z)
{
  S3L_Index index = 0;
  S3L_Unit *verts = LCR_renderer.mapVerts;

  while (index < LCR_renderer.mapModel.vertexCount) // if exists, return index
  {
    if (verts[0] == x && verts[1] == y && verts[2] == z)
      return index;

    verts += 3;
    index++;
  }

  // if it doesn't exist, add it
  if (LCR_renderer.mapModel.vertexCount < LCR_SETTING_MAX_MAP_VERTICES)
  {
    *verts = x; verts++;
    *verts = y; verts++;
    *verts = z;
    LCR_renderer.mapModel.vertexCount++;
    return LCR_renderer.mapModel.vertexCount - 1;
  }

  LCR_LOG0("couldn't add map vertex!");

  return 0;  
}

void _LCR_rendererAddMapTri(S3L_Index a, S3L_Index b, S3L_Index c, uint8_t mat)
{
  if (LCR_renderer.mapModel.triangleCount < LCR_SETTING_MAX_MAP_TRIANGLES)
  {
    S3L_Index *t =
      &(LCR_renderer.mapTris[LCR_renderer.mapModel.triangleCount * 3]);

    *t = a; t++;
    *t = b; t++;
    *t = c;

    LCR_renderer.mapTriangleData[LCR_renderer.mapModel.triangleCount] =
      mat;

    LCR_renderer.mapModel.triangleCount++;
  }
}

void _LCR_rendererSwapMapTris(unsigned int index1, unsigned int index2)
{
  uint8_t tmpMat;
  S3L_Index tmpIndex,
    *t1 = LCR_renderer.mapTris + index1 * 3,
    *t2 = LCR_renderer.mapTris + index2 * 3;

  for (int i = 0; i < 3; ++i)
  {
    tmpIndex = t1[i];
    t1[i] = t2[i];
    t2[i] = tmpIndex;
  }

  tmpMat = LCR_renderer.mapTriangleData[index1];
  LCR_renderer.mapTriangleData[index1] = LCR_renderer.mapTriangleData[index2];
  LCR_renderer.mapTriangleData[index2] = tmpMat;
}

int _LCR_rendererQuadCoversTri(const S3L_Unit quad[8], const S3L_Unit tri[6])
{
  for (int i = 0; i < 3; ++i) // for each triangle point
  {
    int covered = 0;

    for (int j = 0; j < 3; ++j) // for each quad subtriangle
    {
      uint8_t winds = 0;

      for (int k = 0; k < 3; ++k) // for each subtriangle side
      {
         S3L_Unit w = // triangle winding
          (quad[(2 * (j + ((k + 1) % 3))) % 8 + 1] -
            quad[(2 * (j + k)) % 8 + 1]) *
          (tri[2 * i] - quad[(2 * (j + (k + 1) % 3)) % 8]) -
          (quad[(2 * (j + ((k + 1) % 3))) % 8] - quad[(2 * (j + k)) % 8])
          * (tri[2 * i + 1] - quad[(2 * (j + (k + 1) % 3)) % 8 + 1]);

         if (w > 0)
           winds |= 1;
         else if (w < 0)
           winds |= 2;
      }

      if (winds != 3) // no opposite winds?
      {
        covered = 1;
        break;
      }
    }

    if (!covered)
      return 0;
  }

  return 1;
}

/**
  Checks whether two triangles (and potenrially their neighbors) cover each
  other, in return values lowest bit means whether t1 is covered and the second
  lowest bit means whether t2 is covered.
*/
uint8_t _LCR_rendererCheckMapTriCover(const S3L_Index *t1,
  const S3L_Index *t2)
{
  if ((t1[0] == t2[0] || t1[0] == t2[1] || t1[0] == t2[2]) &&
    (t1[1] == t2[0] || t1[1] == t2[1] || t1[1] == t2[2]) &&
    (t1[2] == t2[0] || t1[2] == t2[1] || t1[2] == t2[2]))
    return 0x03;

  uint8_t result = 0;
  int plane = -1;
  S3L_Unit *vertices[6];

  for (int i = 0; i < 3; ++i)
  {
    vertices[i] = LCR_renderer.mapVerts + 3 * t1[i];
    vertices[3 + i] = LCR_renderer.mapVerts + 3 * t2[i];
  }

  for (int i = 0; i < 3; ++i)
    if (vertices[0][i] == vertices[1][i] && vertices[1][i] == vertices[2][i] &&
        vertices[2][i] == vertices[3][i] && vertices[3][i] == vertices[4][i] &&
        vertices[4][i] == vertices[5][i])
    {
      plane = i;
      break;
    }

  if (plane >= 0) // both triangles in the same plane => then do more checks
  {
    if (S3L_abs(vertices[0][0] - vertices[3][0]) +
        S3L_abs(vertices[0][1] - vertices[3][1]) +
        S3L_abs(vertices[0][2] - vertices[3][2]) >
        2 * LCR_RENDERER_UNIT)
      return 0; // quick manhattan distance bailout condition

    for (int j = 0; j < 2; ++j)
    {
      S3L_Unit points2D[14]; // tri1, quad (tri2 + 1 extra vert)

      int coordX = plane == 0 ? 1 : 0,
          coordY = plane == 2 ? 1 : 2;

      for (int i = 0; i < 3; ++i)
      {
        points2D[i * 2]         = vertices[i][coordX];
        points2D[i * 2 + 1]     = vertices[i][coordY];
        points2D[6 + i * 2]     = vertices[3 + i][coordX];
        points2D[6 + i * 2 + 1] = vertices[3 + i][coordY];
      }

      points2D[12] = (4 * points2D[6] + 3 * points2D[8] + points2D[10]) / 8;
      points2D[13] = (4 * points2D[7] + 3 * points2D[9] + points2D[11]) / 8;

      // first: does the triangle alone cover the other one?
      if (_LCR_rendererQuadCoversTri(points2D + 6,points2D))
        result |= 1 << j;
      else
      {
        // now check if this triangle along with a neighbor cover the other one

        S3L_Index *t3 = LCR_renderer.mapTris;

        for (int i = 0; i < LCR_renderer.mapModel.triangleCount; ++i)
        {
          uint8_t sharedVerts =
            (t3[0] == t2[0] || t3[0] == t2[1] || t3[0] == t2[2]) |
            ((t3[1] == t2[0] || t3[1] == t2[1] || t3[1] == t2[2]) << 1) |
            ((t3[2] == t2[0] || t3[2] == t2[1] || t3[2] == t2[2]) << 2);

          if (t3 != t1 && t3 != t2 &&
            (sharedVerts == 3 || sharedVerts == 5 || sharedVerts == 6) &&
            LCR_renderer.mapVerts[3 * t3[0] + plane] ==
            LCR_renderer.mapVerts[3 * t3[1] + plane] &&
            LCR_renderer.mapVerts[3 * t3[1] + plane] ==
            LCR_renderer.mapVerts[3 * t3[2] + plane] &&
            LCR_renderer.mapVerts[3 * t3[0] + plane] ==
            LCR_renderer.mapVerts[3 * t1[0] + plane])
          {
            // here shares exactly two vertices and is in the same plane

            uint8_t freeVert =
              sharedVerts == 3 ? 2 : (sharedVerts == 5 ? 1 : 0);

            points2D[12] = LCR_renderer.mapVerts[3 * t3[freeVert] + coordX];
            points2D[13] = LCR_renderer.mapVerts[3 * t3[freeVert] + coordY];
           
            if (_LCR_rendererQuadCoversTri(points2D + 6,points2D))
            {
              result |= 1 << j;
              break;
            }
          }

          t3 += 3;
        }
      }

      // now swap both triangles and do it all again:

      const S3L_Index *tmp = t1;
      t1 = t2;
      t2 = tmp;

      for (int i = 0; i < 3; ++i)
      {
        S3L_Unit *tmpCoord = vertices[i];
        vertices[i] = vertices[3 + i];
        vertices[3 + i] = tmpCoord;
      }
    }
  }

  return result;
}

/**
  Removes map triangles that are covered by other triangles (and also vertices
  that by this become unused). This makes the map model smaller, faster and
  prevents bleeding through due to z-bugger imprecisions.
*/
void _LCR_cullHiddenMapTris(void)
{
  LCR_LOG1("culling invisible triangles");

  int n = 0; // number of removed elements
  int i = 0;

  S3L_Index *t1 = LCR_renderer.mapTris, *t2;

  /*
    We'll be moving the covered triangles to the end of the array, then at the
    end we'll just shorten the array by number of removed triangles.
  */
  while (i < LCR_renderer.mapModel.triangleCount - n)
  {
    t2 = t1 + 3; // t2 is the the other triangle against which we check

    int t1Covered = 0;

    for (int j = i + 1; j < LCR_renderer.mapModel.triangleCount; ++j)
    {
      uint8_t cover = _LCR_rendererCheckMapTriCover(t1,t2);

      t1Covered |= cover & 0x01;

      if (cover & 0x02)
      {
        if (j < LCR_renderer.mapModel.triangleCount - n)
        {
          _LCR_rendererSwapMapTris(j,
            LCR_renderer.mapModel.triangleCount - 1 - n);

          n++;
        }
      }
 
      t2 += 3; // check next triangle
    }

    if (t1Covered)
    {
      _LCR_rendererSwapMapTris(i,
        LCR_renderer.mapModel.triangleCount - 1 - n);

      n++;
      // we stay at this position because we've swapped the triangle here
    }
    else
    {
      t1 += 3;
      i++;
    }
  }

  LCR_renderer.mapModel.triangleCount -= n; // cut off the removed triangles

  // remove unused vertices:

  i = 0;

  while (i < LCR_renderer.mapModel.vertexCount)
  {
    int used = 0;

    for (int j = 0; j < LCR_renderer.mapModel.triangleCount * 3; ++j)
      if (LCR_renderer.mapTris[j] == i)
      {
        used = 1;
        break;
      }

    if (used)
      i++;
    else
    {
      for (int j = 0; j < 3; ++j)
        LCR_renderer.mapVerts[3 * i + j] =
          LCR_renderer.mapVerts[(LCR_renderer.mapModel.vertexCount - 1) * 3 + j];

      for (int j = 0; j < LCR_renderer.mapModel.triangleCount * 3; ++j)
        if (LCR_renderer.mapTris[j] == LCR_renderer.mapModel.vertexCount - 1)
          LCR_renderer.mapTris[j] = i;

      LCR_renderer.mapModel.vertexCount--;
    }
  }
}

void _LCR_makeMapChunks(void)
{
  LCR_LOG1("making map chunks");

  S3L_Index start = 0;

  for (int chunkNo = 0; chunkNo < LCR_RENDERER_CHUNKS_TOTAL; ++chunkNo)
  {
    S3L_Unit chunkCorner[3];
    const S3L_Index *tri = LCR_renderer.mapTris + 3 * start;

    LCR_renderer.chunkStarts[chunkNo] = start;

    chunkCorner[0] = (chunkNo & 0x03) * LCR_RENDERER_CHUNK_SIZE_HORIZONTAL;
    chunkCorner[1] = ((chunkNo >> 2) & 0x03) * (LCR_RENDERER_CHUNK_SIZE_HORIZONTAL / 2);
    chunkCorner[2] = ((chunkNo >> 4) & 0x03) * LCR_RENDERER_CHUNK_SIZE_HORIZONTAL;

    chunkCorner[0] -= LCR_MAP_SIZE_BLOCKS * LCR_RENDERER_UNIT / 2;
    chunkCorner[1] -= LCR_MAP_SIZE_BLOCKS * LCR_RENDERER_UNIT / 4;
    chunkCorner[2] -= LCR_MAP_SIZE_BLOCKS * LCR_RENDERER_UNIT / 2;
 
    for (int i = start; i < LCR_renderer.mapModel.triangleCount; ++i)
    {
      const S3L_Unit *v = LCR_renderer.mapVerts + 3 * tri[0];

      if (v[0] >= chunkCorner[0] &&
          v[0] < chunkCorner[0] + LCR_RENDERER_CHUNK_SIZE_HORIZONTAL &&
          v[1] >= chunkCorner[1] &&
          v[1] < chunkCorner[1] + (LCR_RENDERER_CHUNK_SIZE_HORIZONTAL / 2) &&
          v[2] >= chunkCorner[2] &&
          v[2] < chunkCorner[2] + LCR_RENDERER_CHUNK_SIZE_HORIZONTAL)
      {
        _LCR_rendererSwapMapTris(i,start);
        start++;
      }

      tri += 3;
    }
  }
}

/**
  Builds the internal 3D model of the currently loaded map. Returns 1 on
  success, 0 otherwise (e.g. not enough space).
*/
uint8_t _LCR_buildMapModel(void)
{
  LCR_LOG1("building map model");

  uint8_t blockShapeBytes[LCR_MAP_BLOCK_SHAPE_MAX_BYTES];
  uint8_t blockShapeByteCount;

  S3L_model3DInit(LCR_renderer.mapVerts,0,LCR_renderer.mapTris,0,
    &LCR_renderer.mapModel);

  LCR_renderer.mapModel.transform.scale.x =
    (_LCR_MAP_MODEL_SCALE * S3L_F) / 1024;
  LCR_renderer.mapModel.transform.scale.y
    = LCR_renderer.mapModel.transform.scale.x;
  LCR_renderer.mapModel.transform.scale.z
    = LCR_renderer.mapModel.transform.scale.x;

  for (int j = 0; j < LCR_currentMap.blockCount; ++j)
  {
    if ((j + 1) % LCR_SETTING_TRIANGLE_CULLING_PERIOD == 0)
      _LCR_cullHiddenMapTris();

    S3L_Unit originOffset = -1 * LCR_MAP_SIZE_BLOCKS / 2 * LCR_RENDERER_UNIT;
    S3L_Index triIndices[3];
    const uint8_t *block = LCR_currentMap.blocks + j * LCR_BLOCK_SIZE;
    uint8_t
      blockType = block[0],
      edgeBits,   // bottom, top, left, right, front, bottom
      bx, by, bz, // block coords
      vx, vy, vz, // vertex coords
      vi = 0;     // vertex index (0, 1 or 2)

    LCR_mapBlockGetCoords(block,&bx,&by,&bz);

    LCR_mapGetBlockShape(blockType,LCR_mapBlockGetTransform(block),
      blockShapeBytes,&blockShapeByteCount);

    for (int i = 0; i < blockShapeByteCount; ++i)
    {
      if (vi == 0)
        edgeBits = (by == 0) |
          ((by == LCR_MAP_SIZE_BLOCKS - 1) << 1) |
          ((bx == 0) << 2) |
          ((bx == LCR_MAP_SIZE_BLOCKS - 1) << 3) |
          ((bz == 0) << 4) |
          ((bz == LCR_MAP_SIZE_BLOCKS - 1) << 5);

      LCR_decodeMapBlockCoords(blockShapeBytes[i],&vx,&vy,&vz);

      edgeBits &= (vy == 0) | ((vy == LCR_BLOCK_SHAPE_COORD_MAX) << 1) |
        ((vx == 0) << 2) | ((vx == LCR_BLOCK_SHAPE_COORD_MAX) << 3) |
        ((vz == 0) << 4) | ((vz == LCR_BLOCK_SHAPE_COORD_MAX) << 5);

      triIndices[vi] = _LCR_rendererAddMapVert(
        originOffset + (((S3L_Unit) bx) * LCR_RENDERER_UNIT) +
          (LCR_RENDERER_UNIT * ((S3L_Unit) vx)) / LCR_BLOCK_SHAPE_COORD_MAX,
        (originOffset + (((S3L_Unit) by) * LCR_RENDERER_UNIT)) / 2 +
          (LCR_RENDERER_UNIT / 2 * ((S3L_Unit) vy)) / LCR_BLOCK_SHAPE_COORD_MAX,
        originOffset + (((S3L_Unit) bz) * LCR_RENDERER_UNIT) +
          (LCR_RENDERER_UNIT * ((S3L_Unit) vz)) / LCR_BLOCK_SHAPE_COORD_MAX);

      if (vi < 2)
        vi++;
      else
      {
        // don't add triangles completely at the floor or ceiling of the map
        if (!edgeBits)
        {
          uint8_t triData;

          if (blockType == LCR_BLOCK_CHECKPOINT_0)
            triData = LCR_RENDERER_MAT_CP0 | ((i % 2) << 4);
          else if (blockType == LCR_BLOCK_FINISH)
            triData = LCR_RENDERER_MAT_FIN | ((i % 2) << 4);
          else
          {
            uint8_t blockMat = LCR_mapBlockGetMaterial(block);

#define VERT(n,c) LCR_renderer.mapVerts[3 * n + c]
            triData =
              (((VERT(triIndices[0],0) == VERT(triIndices[1],0)) &&
              (VERT(triIndices[1],0) == VERT(triIndices[2],0))) << 4) |
              (((VERT(triIndices[0],2) == VERT(triIndices[1],2)) &&
              (VERT(triIndices[1],2) == VERT(triIndices[2],2))) << 5);
#undef VERT

            if (triData & 0xf0) // wall?
            {
              triData |= 
                ((blockMat == LCR_BLOCK_MATERIAL_CONCRETE) ||
                (blockMat == LCR_BLOCK_MATERIAL_ICE) ||
                (blockType == LCR_BLOCK_FULL_ACCEL) ||
                (blockType == LCR_BLOCK_FULL_FAN)) ?
                LCR_IMAGE_WALL_CONCRETE : LCR_IMAGE_WALL_WOOD;
            }
            else
            { // TODO: tidy this mess?
              if (blockType == LCR_BLOCK_FULL_ACCEL)
                triData |= LCR_IMAGE_GROUND_ACCEL;
              else if (blockType == LCR_BLOCK_FULL_FAN)
                triData |= LCR_IMAGE_GROUND_FAN;
              else
                switch (blockMat)
                {
                  case LCR_BLOCK_MATERIAL_CONCRETE:
                    triData |= LCR_IMAGE_GROUND_CONCRETE;
                    break;

                  case LCR_BLOCK_MATERIAL_GRASS:
                    triData |= LCR_IMAGE_GROUND_GRASS;
                    break;

                  case LCR_BLOCK_MATERIAL_DIRT:
                    triData |= LCR_IMAGE_GROUND_DIRT;
                    break;

                  case LCR_BLOCK_MATERIAL_ICE:
                    triData |= LCR_IMAGE_GROUND_ICE;
                    break;

                  default:
                    break;
                }
            }
          }

          _LCR_rendererAddMapTri(triIndices[0],triIndices[1],triIndices[2],
            triData);
        }      
     
        vi = 0;
      }
    }
  }

  _LCR_cullHiddenMapTris();

  LCR_LOG1("map model built");

  return 1;
}

void _LCR_rendererComputeLOD(void)
{
  LCR_LOG1("computing LOD");

  for (int i = 0; i < LCR_RENDERER_LOD_BLOCKS; ++i)
    LCR_renderer.gridOfLODs[i] = 0;

  for (int i = 0; i < LCR_currentMap.blockCount; ++i)
  {
    uint8_t x, y, z;

    LCR_mapBlockGetCoords(LCR_currentMap.blocks + i * LCR_BLOCK_SIZE,&x,&y,&z);

    x /= 8;
    y /= 8;
    z /= 8;

    LCR_renderer.gridOfLODs[z * 8 + y] |= (0x01 << x);
  }
}

void LCR_rendererMarkTakenCP(int x, int y, int z)
{
  for (int i = 0; i < LCR_renderer.mapModel.triangleCount; ++i)
    if ((LCR_renderer.mapTriangleData[i] & 0x0f) == LCR_RENDERER_MAT_CP0)
    {
      S3L_Unit point[3];

      point[0] = 0;
      point[1] = 0;
      point[2] = 0;

      for (int j = 0; j < 2; ++j)
        for (int k = 0; k < 3; ++k)
          point[k] += LCR_renderer.mapModel.vertices[
            3 * LCR_renderer.mapModel.triangles[3 * i + j] + k] +
              (LCR_MAP_SIZE_BLOCKS / 2) *
                (k == 1 ? LCR_RENDERER_UNIT / 2 : LCR_RENDERER_UNIT);

      point[0] /= 2;
      point[1] /= 2;
      point[2] /= 2;

      if (point[0] / LCR_RENDERER_UNIT == x &&
        point[1] / (LCR_RENDERER_UNIT / 2) == y &&
        point[2] / LCR_RENDERER_UNIT == z)
        LCR_renderer.mapTriangleData[i] = (LCR_renderer.mapTriangleData[i]
          & 0xf0) | LCR_RENDERER_MAT_CP1;
    }
}

/**
  Call to reset currently loaded map, i.e. mark all checkpoints as untaken etc.
*/
void LCR_rendererRestart(void)
{
  for (int i = 0; i < LCR_renderer.mapModel.triangleCount; ++i)
    if ((LCR_renderer.mapTriangleData[i] & 0x0f) == LCR_RENDERER_MAT_CP1)
      LCR_renderer.mapTriangleData[i] = (LCR_renderer.mapTriangleData[i] & 0xf0)
        | LCR_RENDERER_MAT_CP0;
}

uint8_t LCR_rendererInit(void)
{
  LCR_LOG0("initializing renderer");

  LCR_renderer.frame = 0;

  if (!_LCR_buildMapModel())
    return 0;

  _LCR_makeMapChunks();
  _LCR_rendererComputeLOD();

  LCR_renderer.carModel = LCR_renderer.models + 8;
  LCR_renderer.ghostModel = LCR_renderer.models + 9;

  S3L_model3DInit(
#if LCR_ANIMATE_CAR
    LCR_renderer.animatedCarVerts
#else
    LCR_carVertices
#endif
    ,LCR_CAR_VERTEX_COUNT,
    LCR_carTriangles,LCR_CAR_TRIANGLE_COUNT,
    LCR_renderer.carModel);

  S3L_vec4Set(&(LCR_renderer.carModel->transform.scale),
    LCR_RENDERER_CAR_SCALE,LCR_RENDERER_CAR_SCALE,LCR_RENDERER_CAR_SCALE,0);

  S3L_model3DInit(LCR_carVertices,LCR_CAR_VERTEX_COUNT,LCR_carTriangles,
    LCR_CAR_TRIANGLE_COUNT,LCR_renderer.ghostModel);

  LCR_renderer.ghostModel->transform.scale =
    LCR_renderer.carModel->transform.scale; 

LCR_renderer.ghostModel->transform.translation.x -= LCR_GAME_UNIT / 4;

#if LCR_ANIMATE_CAR
  for (int i = 0; i < LCR_CAR_VERTEX_COUNT * 3; ++i)
    LCR_renderer.animatedCarVerts[i] = LCR_carVertices[i];

  int count[2];
  count[0] = 0;
  count[1] = 0;

  for (int i = 0; i < 4; ++i)
    LCR_renderer.wheelRotationCenters[i] = 0;

  for (int i = 0; i < LCR_CAR_VERTEX_COUNT; ++i)
    if (LCR_carVertexTypes[i] > 0) // wheel?
    {
      uint8_t front = LCR_carVertexTypes[i] == 1;

      LCR_renderer.wheelRotationCenters[0 + 2 * front] +=
        LCR_carVertices[3 * i + 2];
      LCR_renderer.wheelRotationCenters[1 + 2 * front] +=
        LCR_carVertices[3 * i + 1];

      count[front]++;
    }

  LCR_renderer.wheelRotationCenters[0] /= count[0];
  LCR_renderer.wheelRotationCenters[1] /= count[0];
  LCR_renderer.wheelRotationCenters[2] /= count[1];
  LCR_renderer.wheelRotationCenters[3] /= count[1];

  LCR_renderer.wheelRotation = 0;
  LCR_renderer.wheelSteer = 0;
#endif

  LCR_LOG2("initializing 3D scene");

  S3L_sceneInit(
    LCR_renderer.models,LCR_RENDERER_MODEL_COUNT,&LCR_renderer.scene);

  return 1;
}

void LCR_rendererGetCameraTransform(LCR_GameUnit position[3],
  LCR_GameUnit rotation[3], LCR_GameUnit *fov)
{
  position[0] = (LCR_renderer.scene.camera.transform.translation.x *
    LCR_GAME_UNIT) / LCR_RENDERER_UNIT;
  position[1] = (LCR_renderer.scene.camera.transform.translation.y *
    LCR_GAME_UNIT) / LCR_RENDERER_UNIT;
  position[2] = (LCR_renderer.scene.camera.transform.translation.z *
    LCR_GAME_UNIT) / LCR_RENDERER_UNIT;

  rotation[0] = (LCR_renderer.scene.camera.transform.rotation.x *
    LCR_GAME_UNIT) / S3L_F;
  rotation[1] = (LCR_renderer.scene.camera.transform.rotation.y *
    LCR_GAME_UNIT) / S3L_F;
  rotation[2] = (LCR_renderer.scene.camera.transform.rotation.z *
    LCR_GAME_UNIT) / S3L_F;

  *fov = (LCR_renderer.scene.camera.focalLength * LCR_GAME_UNIT)
    / S3L_F;
}

void LCR_rendererMoveCamera(LCR_GameUnit forwRightUpOffset[3],
  LCR_GameUnit yawPitchOffset[2])
{  
  LCR_LOG2("moving camera");

  S3L_Vec4 f, r, u;

  S3L_rotationToDirections(LCR_renderer.scene.camera.transform.rotation,
    S3L_F,&f,&r,&u);

  LCR_renderer.scene.camera.transform.translation.x +=
    ((f.x * forwRightUpOffset[0] + r.x * forwRightUpOffset[1] + 
    u.x * forwRightUpOffset[2]) * S3L_F) / LCR_GAME_UNIT;      
 
  LCR_renderer.scene.camera.transform.translation.y +=
    ((f.y * forwRightUpOffset[0] + r.y * forwRightUpOffset[1] + 
    u.y * forwRightUpOffset[2]) * S3L_F) / LCR_GAME_UNIT;      

  LCR_renderer.scene.camera.transform.translation.z +=
    ((f.z * forwRightUpOffset[0] + r.z * forwRightUpOffset[1] + 
    u.z * forwRightUpOffset[2]) * S3L_F) / LCR_GAME_UNIT;      

  LCR_renderer.scene.camera.transform.rotation.y +=
    (yawPitchOffset[0] * S3L_F) / LCR_GAME_UNIT;

  LCR_renderer.scene.camera.transform.rotation.x +=
    (yawPitchOffset[1] * S3L_F) / LCR_GAME_UNIT;
 
#define chk(o,c,l) \
  if (LCR_renderer.scene.camera.transform.translation.c o l) \
    LCR_renderer.scene.camera.transform.translation.c = l;

chk(<,x,-1 * LCR_MAP_SIZE_BLOCKS * LCR_RENDERER_UNIT / 2)
chk(>,x,LCR_MAP_SIZE_BLOCKS * LCR_RENDERER_UNIT / 2)
chk(<,y,-1 * LCR_MAP_SIZE_BLOCKS * LCR_RENDERER_UNIT / 4)
chk(>,y,LCR_MAP_SIZE_BLOCKS * LCR_RENDERER_UNIT / 4)
chk(<,z,-1 * LCR_MAP_SIZE_BLOCKS * LCR_RENDERER_UNIT / 2)
chk(>,z,LCR_MAP_SIZE_BLOCKS * LCR_RENDERER_UNIT / 2)

}

/**
  Fast and safe rect drawing function (handles out of screen coords).
*/
void LCR_rendererDrawRect(int x, int y, unsigned int w, unsigned int h,
  uint16_t color, int dither)
{
  if (x >= LCR_EFFECTIVE_RESOLUTION_X || y >= LCR_EFFECTIVE_RESOLUTION_Y)
    return;

  if (x < 0)
  {
    if (-1 * x >= ((int) w))
      return;

    w += x;
    x = 0;
  }

  if (x + w > LCR_EFFECTIVE_RESOLUTION_X)
    w = LCR_EFFECTIVE_RESOLUTION_X - x;

  if (y < 0)
  {
    if (-1 * y > ((int) h))
      return;

    h += y;
    y = 0;
  }

  if (y + h > LCR_EFFECTIVE_RESOLUTION_Y)
    h = LCR_EFFECTIVE_RESOLUTION_Y - y;

  unsigned long index = y * LCR_EFFECTIVE_RESOLUTION_X + x;

  if (dither)
  {
    uint8_t parity = (x % 2) == (y % 2);

    for (unsigned int i = 0; i < h; ++i)
    {
      for (unsigned int j = ((i % 2) == parity); j < w; j += 2)
        LCR_drawPixel(index + j,color);

      index += LCR_EFFECTIVE_RESOLUTION_X;
    }  
  }
  else
    for (unsigned int i = 0; i < h; ++i)
    {
      for (unsigned int j = 0; j < w; ++j)
      {
        LCR_drawPixel(index,color);
        index++;
      }

      index += LCR_EFFECTIVE_RESOLUTION_X - w;
    }
}

void _LCR_rendererDrawLODBlock(int blockX, int blockY, int blockZ, unsigned int size,
  uint16_t color, uint8_t variability)
{
  LCR_LOG2("drawing LOD block");

  S3L_Vec4 p, r;

  p.x = (blockX - LCR_MAP_SIZE_BLOCKS / 2) * LCR_RENDERER_UNIT
    + LCR_RENDERER_UNIT / 2;

  p.y = (blockY - LCR_MAP_SIZE_BLOCKS / 2) * (LCR_RENDERER_UNIT / 2)
    + LCR_RENDERER_UNIT / 4;

  p.z = (blockZ - LCR_MAP_SIZE_BLOCKS / 2) * LCR_RENDERER_UNIT
    + LCR_RENDERER_UNIT / 2;

  p.w = size;

  S3L_project3DPointToScreen(p,LCR_renderer.scene.camera,&r);

  if (r.w > 0 && r.z > LCR_SETTING_LOD_DISTANCE * LCR_RENDERER_UNIT &&
    r.w < LCR_EFFECTIVE_RESOLUTION_X)
  {
    switch (variability % 4)
    {
      case 0:  r.w += r.w / 4; r.x += LCR_BLOCK_SIZE / 8; break;
      case 1:  r.w += r.w / 8; r.y -= LCR_BLOCK_SIZE / 16; break;
      case 2:  r.w += r.w / 4; break;
      default: r.z += LCR_BLOCK_SIZE / 8; break;
    }

    if (variability % 8 < 5)
      LCR_rendererDrawRect(r.x - r.w / 2,r.y - r.w / 2,r.w,r.w,color,1);
    else
    {
      r.w /= 2;
      LCR_rendererDrawRect(r.x - r.w / 2,r.y - r.w / 2,r.w,r.w,color,1);
      r.w += r.w / 2;
      LCR_rendererDrawRect(r.x - r.w / 8,r.y - r.w / 4,r.w,r.w,color,1);
    }
  }
}

/**
  Draws background sky, offsets are in multiples of screen dimensions
  (e.g. S3L_F / 2 for offsetH means half the screen width).
*/
void LCR_rendererDrawSky(int sky, S3L_Unit offsetH, S3L_Unit offsetV)
{
  LCR_LOG2("drawing sky");

  int anchorPoint[2], y;
  unsigned long pixelIndex;
  unsigned int topColor, bottomColor;

  sky = 8 + 4 * sky;

  LCR_loadImage(sky);
  topColor = LCR_sampleImage(0,0);

  LCR_loadImage(sky + 3);
  bottomColor = LCR_sampleImage(LCR_IMAGE_SIZE - 1,LCR_IMAGE_SIZE - 1);

  anchorPoint[0] = ((LCR_EFFECTIVE_RESOLUTION_X * offsetH)
    / S3L_F) %
    (2 * LCR_IMAGE_SIZE * LCR_SETTING_SKY_SIZE);

  if (anchorPoint[0] < 0)
    anchorPoint[0] += 2 * LCR_IMAGE_SIZE * LCR_SETTING_SKY_SIZE;

  anchorPoint[1] = 
    (LCR_EFFECTIVE_RESOLUTION_Y) / 3 - // 3: we place the center a bit more up
    (LCR_EFFECTIVE_RESOLUTION_Y * offsetV) / S3L_F
    - LCR_IMAGE_SIZE * LCR_SETTING_SKY_SIZE;
  
  pixelIndex = 0;
  y = anchorPoint[1] < 0 ? anchorPoint[1] : 0;

  while (y < anchorPoint[1] && y < LCR_EFFECTIVE_RESOLUTION_Y) // top strip
  {
    for (int x = 0; x < LCR_EFFECTIVE_RESOLUTION_X; ++x)
    {
      LCR_drawPixel(pixelIndex,topColor);
      pixelIndex++;
    }

    y++;
  }

  anchorPoint[1] += 2 * LCR_IMAGE_SIZE * LCR_SETTING_SKY_SIZE;
    
  int linesLeft = 0;
  int skyPart = 0;

  while (y < anchorPoint[1] && y < LCR_EFFECTIVE_RESOLUTION_Y) // image strip
  {
    if (!linesLeft)
    {
      LCR_loadImage(sky + skyPart);
      linesLeft = LCR_IMAGE_SIZE / 2;
      skyPart++;
    }

    if (y >= 0)
    {
      for (int ix = 0; ix < 2 * LCR_IMAGE_SIZE * LCR_SETTING_SKY_SIZE;
        ix += LCR_SETTING_SKY_SIZE)
      {
        unsigned int color = LCR_getNextImagePixel();
        unsigned long startIndex = pixelIndex;

        for (int k = 0; k < LCR_SETTING_SKY_SIZE; ++k)
        {
          if (y + k >= LCR_EFFECTIVE_RESOLUTION_Y)
            break;

          for (int j = 0; j < LCR_SETTING_SKY_SIZE; ++j)
          {
            int x = anchorPoint[0] + ix + j;

            if (x >= 2 * LCR_IMAGE_SIZE * LCR_SETTING_SKY_SIZE)
              x -= 2 * LCR_IMAGE_SIZE * LCR_SETTING_SKY_SIZE;

            while (x < LCR_EFFECTIVE_RESOLUTION_X)
            {
              LCR_drawPixel(startIndex + x,color);
              x += 2 * LCR_IMAGE_SIZE * LCR_SETTING_SKY_SIZE;
            }
          }

          startIndex += LCR_EFFECTIVE_RESOLUTION_X;
        }
      }
    
      pixelIndex += LCR_EFFECTIVE_RESOLUTION_X * LCR_SETTING_SKY_SIZE;
      y += LCR_SETTING_SKY_SIZE;
    }
    else
    {
      for (int ix = 0; ix < 2 * LCR_IMAGE_SIZE; ++ix)
        LCR_getNextImagePixel();
   
      for (int i = 0; i < LCR_SETTING_SKY_SIZE; ++i)
      {
        if (y >= 0)
          for (int x = 0; x < LCR_EFFECTIVE_RESOLUTION_X; ++x)
          {
            LCR_drawPixel(pixelIndex,topColor);
            pixelIndex++;
          }

        y++;
      }
    }

    linesLeft--;
  }

  while (y < 0) // can still be the case
    y = 0;

  while (y < LCR_EFFECTIVE_RESOLUTION_Y) // bottom strip
  {
    for (int x = 0; x < LCR_EFFECTIVE_RESOLUTION_X; ++x)
    {
      LCR_drawPixel(pixelIndex,bottomColor);
      pixelIndex++;
    }

    y++;
  }
}

void _LCR_rendererLoadMapChunk(uint8_t chunk, int8_t x, int8_t y, int8_t z)
{
  LCR_renderer.models[chunk] = LCR_renderer.mapModel;

  if (x < 0 || x >= LCR_RENDERER_CHUNK_RESOLUTION ||
      y < 0 || y >= LCR_RENDERER_CHUNK_RESOLUTION ||
      z < 0 || z >= LCR_RENDERER_CHUNK_RESOLUTION)
  {
    LCR_renderer.models[chunk].triangleCount = 0;
    LCR_renderer.loadedChunks[chunk] = 0;
  }
  else
  {
    int blockNum = x | (y << 2) | (z << 4);

    LCR_renderer.loadedChunks[chunk] = blockNum;

    int triCount =
      (blockNum == LCR_RENDERER_CHUNKS_TOTAL - 1 ?
      (LCR_renderer.mapModel.triangleCount - 1) :
        LCR_renderer.chunkStarts[blockNum + 1])
        - LCR_renderer.chunkStarts[blockNum];

    if (triCount < 0)
      triCount = 0;

    LCR_renderer.models[chunk].triangles =
      LCR_renderer.mapTris + LCR_renderer.chunkStarts[blockNum] * 3;

    LCR_renderer.models[chunk].triangleCount = triCount;
  }
}

/**
  Serves for smoothing out angle change, e.g. that of camera rotation.
*/
S3L_Unit _LCR_rendererSmoothRot(S3L_Unit angleOld, S3L_Unit angleNew,
  unsigned int amount)
{
  /* We have to do the following angle correction -- even if keep angles in
  correct range at the start of frame, subsequent steps may alter the rotations
  and here we could end up with bad ranges again. */
  S3L_Unit angleDiff = S3L_wrap(angleNew,S3L_F) - S3L_wrap(angleOld,S3L_F);

  if (angleDiff == 0)
    return angleNew;

  S3L_Unit angleDiffAbs = S3L_abs(angleDiff);

  if (angleDiffAbs > S3L_F / 2) // consider e.g. 350 degrees minus 1 degree
  {
    angleDiffAbs = S3L_F - angleDiffAbs;
    angleDiff = (angleDiff > 0) ? -1 * angleDiffAbs : angleDiffAbs;
  }

  if (angleDiffAbs > (3 * S3L_F) / 8) // angle too big, rotate immediately
    return angleNew;

  return angleOld + (angleDiff / S3L_nonZero(amount));
}

/**
  Loads the map models with 8 chunks that are nearest to a certain point
  towards which camera is looking.
*/
void _LCR_rendererLoadMapChunks(void)
{
  LCR_LOG2("loading map chunks");

  int8_t camChunk[3], chunkOffsets[3];
  S3L_Vec4 cp = LCR_renderer.scene.camera.transform.translation;
  S3L_Vec4 cf;
  
  S3L_rotationToDirections(LCR_renderer.scene.camera.transform.rotation,
    LCR_RENDERER_CHUNK_SIZE_HORIZONTAL / 2,&cf,0,0);

  cp.x += (LCR_MAP_SIZE_BLOCKS * LCR_RENDERER_UNIT) / 2;
  cp.y += (LCR_MAP_SIZE_BLOCKS * LCR_RENDERER_UNIT) / 4;
  cp.z += (LCR_MAP_SIZE_BLOCKS * LCR_RENDERER_UNIT) / 2;

  cf.x += cp.x % LCR_RENDERER_CHUNK_SIZE_HORIZONTAL;
  cf.y += cp.y % (LCR_RENDERER_CHUNK_SIZE_HORIZONTAL / 2);
  cf.z += cp.z % LCR_RENDERER_CHUNK_SIZE_HORIZONTAL;

  camChunk[0] = cp.x / LCR_RENDERER_CHUNK_SIZE_HORIZONTAL;
  camChunk[1] = cp.y / (LCR_RENDERER_CHUNK_SIZE_HORIZONTAL / 2);
  camChunk[2] = cp.z / LCR_RENDERER_CHUNK_SIZE_HORIZONTAL;

  chunkOffsets[0] =
    (cf.x >= (LCR_RENDERER_CHUNK_SIZE_HORIZONTAL / 2)) ? 1 : -1;

  chunkOffsets[1] =
    (cf.y >= (LCR_RENDERER_CHUNK_SIZE_HORIZONTAL / 4)) ? 1 : -1;

  chunkOffsets[2] =
    (cf.z >= (LCR_RENDERER_CHUNK_SIZE_HORIZONTAL / 2)) ? 1 : -1;

  for (uint8_t i = 0; i < 8; ++i)
    _LCR_rendererLoadMapChunk(i,
      camChunk[0] + ((i & 0x01) ? chunkOffsets[0] : 0),
      camChunk[1] + ((i & 0x02) ? chunkOffsets[1] : 0),
      camChunk[2] + ((i & 0x04) ? chunkOffsets[2] : 0));
}

/**
  Draws the LOD overlay.
*/
void LCR_rendererDrawLOD(void)
{
  LCR_LOG2("drawing LOD");

#if LCR_SETTING_LOD_DISTANCE < 64
  int variability = 0;

  for (unsigned int i = 0; i < LCR_RENDERER_LOD_BLOCKS; ++i)
    if (LCR_renderer.gridOfLODs[i])
    {
      uint8_t byte = LCR_renderer.gridOfLODs[i];
      unsigned int bx, by, bz;

      bz = (i / 8) * 8 + 4;
      by = (i % 8) * 8 + 4;

      for (unsigned int j = 0; j < 8; ++j)
      {
        if (byte & 0x01)
        {
          variability = variability < 14 ? variability + 1 : 0;
          bx = j * 8 + 4;

          _LCR_rendererDrawLODBlock(bx,by,bz,(4 * LCR_EFFECTIVE_RESOLUTION_Y)
            / 3,LCR_SETTING_LOD_COLOR,variability);
        }

        byte >>= 1;
      }
    }
#endif
}

void LCR_drawLevelFloor(void)
{
  LCR_LOG2("drawing floor");

#if LCR_SETTING_FLOOR_PARTICLE_SIZE != 0
#define _STEP ((LCR_MAP_SIZE_BLOCKS * LCR_RENDERER_UNIT) / LCR_SETTING_FLOOR_PARTICLE_RESOLUTION)

  S3L_Vec4 floorPoint, projectedPoint;

  floorPoint.z = -1 * (LCR_MAP_SIZE_BLOCKS / 2) * LCR_RENDERER_UNIT + _STEP / 2;
  floorPoint.y = -1 *(LCR_MAP_SIZE_BLOCKS / 2) * (LCR_RENDERER_UNIT / 2);
  floorPoint.w = LCR_SETTING_RESOLUTION_X / LCR_SETTING_FLOOR_PARTICLE_SIZE;

  for (uint8_t j = 0; j < LCR_SETTING_FLOOR_PARTICLE_RESOLUTION; ++j)
  {
    floorPoint.x = -1 * (LCR_MAP_SIZE_BLOCKS / 2) * LCR_RENDERER_UNIT
      + _STEP / 2;

    for (uint8_t i = 0; i < LCR_SETTING_FLOOR_PARTICLE_RESOLUTION; ++i)
    {
      S3L_project3DPointToScreen(floorPoint,LCR_renderer.scene.camera,
        &projectedPoint);
    
      if (projectedPoint.w > 0 && projectedPoint.w < LCR_EFFECTIVE_RESOLUTION_X)
        LCR_rendererDrawRect(projectedPoint.x,projectedPoint.y,
          projectedPoint.w,projectedPoint.w,LCR_SETTING_LOD_COLOR,1);

      floorPoint.x += _STEP;
    }

    floorPoint.z += _STEP;
  }
#undef _STEP
#endif
}

#if LCR_ANIMATE_CAR
void _LCR_rendererAnimateCar(void)
{
  LCR_LOG2("animating car");

  for (int i = LCR_renderer.frame % LCR_SETTING_CAR_ANIMATION_SUBDIVIDE;
    i < LCR_CAR_VERTEX_COUNT; i += LCR_SETTING_CAR_ANIMATION_SUBDIVIDE)
  {
    if (LCR_carVertexTypes[i] > 0)
    {
      S3L_Unit s = S3L_sin(-1 * LCR_renderer.wheelRotation),
               c = S3L_cos(-1 * LCR_renderer.wheelRotation);

      S3L_Unit v[2], tmp; 

      unsigned int index = 3 * i;
      uint8_t offset = (LCR_carVertexTypes[i] == 1) * 2;

      v[0] = LCR_carVertices[index + 2] -
        LCR_renderer.wheelRotationCenters[offset];
      v[1] = LCR_carVertices[index + 1] -
        LCR_renderer.wheelRotationCenters[offset + 1];

      tmp = v[0];
      v[0] = (v[0] * c - v[1] * s) / S3L_F;
      v[1] = (tmp  * s + v[1] * c) / S3L_F;

      LCR_renderer.animatedCarVerts[index + 2] =
        v[0] + LCR_renderer.wheelRotationCenters[offset];
      LCR_renderer.animatedCarVerts[index + 1] =
        v[1] + LCR_renderer.wheelRotationCenters[offset + 1];

      if (LCR_carVertexTypes[i] == 1)
      {
        /* Turn front wheels; this is not real turning but just a fake by
           skewing in Z and X directions. */
        LCR_renderer.animatedCarVerts[index] = LCR_carVertices[index];

        LCR_renderer.animatedCarVerts[index + 2] -=
          (LCR_renderer.animatedCarVerts[index] * LCR_renderer.wheelSteer)
          / (8 * S3L_F);

        LCR_renderer.animatedCarVerts[index] +=
          ((LCR_renderer.animatedCarVerts[index + 2] -
          LCR_renderer.wheelRotationCenters[2]) * LCR_renderer.wheelSteer)
          / (2 * S3L_F);
      }
    }
  }
}
#endif

void LCR_rendererCameraFollow(void)
{
  LCR_LOG2("following camera");

  S3L_Transform3D transPrev = LCR_renderer.scene.camera.transform;

  LCR_renderer.scene.camera.transform.translation.y =
    S3L_clamp(
      LCR_renderer.scene.camera.transform.translation.y,
      LCR_renderer.carModel->transform.translation.y +
      (LCR_SETTING_CAMERA_HEIGHT - LCR_SETTING_CAMERA_HEIGHT_BAND) *
        LCR_RENDERER_UNIT / 8,
      LCR_renderer.carModel->transform.translation.y +
      (LCR_SETTING_CAMERA_HEIGHT + LCR_SETTING_CAMERA_HEIGHT_BAND) *
        LCR_RENDERER_UNIT / 8);

  S3L_Vec4 toCam = LCR_renderer.scene.camera.transform.translation;

  S3L_vec3Sub(&toCam,LCR_renderer.carModel->transform.translation);

  S3L_Unit horizontalDist = S3L_sqrt(toCam.x * toCam.x + toCam.z * toCam.z);

  if (horizontalDist == 0)
  {
    toCam.z = 1;
    horizontalDist = 1;
  }

  S3L_Unit horizontalDistNew =
    S3L_clamp(horizontalDist,
      (LCR_SETTING_CAMERA_DISTANCE - LCR_SETTING_CAMERA_DISTANCE_BAND)
      * (LCR_RENDERER_UNIT / 4),
      (LCR_SETTING_CAMERA_DISTANCE + LCR_SETTING_CAMERA_DISTANCE_BAND)
      * (LCR_RENDERER_UNIT / 4));

  if (horizontalDistNew != horizontalDist)
  {
    toCam.x = (toCam.x * horizontalDistNew) / horizontalDist;
    toCam.z = (toCam.z * horizontalDistNew) / horizontalDist;

    LCR_renderer.scene.camera.transform.translation.x =
      LCR_renderer.carModel->transform.translation.x +
      (toCam.x * horizontalDistNew) / horizontalDist;

    LCR_renderer.scene.camera.transform.translation.z =
      LCR_renderer.carModel->transform.translation.z +
      (toCam.z * horizontalDistNew) / horizontalDist;
  }

  S3L_lookAt(LCR_renderer.carModel->transform.translation,
    &(LCR_renderer.scene.camera.transform));

#if LCR_SETTING_SMOOTH_ANIMATIONS
  // now average with previous transform to smooth the animation out:

  S3L_vec3Add(&(LCR_renderer.scene.camera.transform.translation),
  transPrev.translation);

  LCR_renderer.scene.camera.transform.translation.x /= 2;
  LCR_renderer.scene.camera.transform.translation.y /= 2;
  LCR_renderer.scene.camera.transform.translation.z /= 2;
 
  LCR_renderer.scene.camera.transform.rotation.x = _LCR_rendererSmoothRot(
    transPrev.rotation.x,LCR_renderer.scene.camera.transform.rotation.x,8);

  LCR_renderer.scene.camera.transform.rotation.y = _LCR_rendererSmoothRot(
    transPrev.rotation.y,LCR_renderer.scene.camera.transform.rotation.y,6);
#endif
}

void LCR_rendererSetWheelState(LCR_GameUnit rotation, LCR_GameUnit steer)
{
#if LCR_ANIMATE_CAR
  LCR_renderer.wheelRotation = rotation;
  LCR_renderer.wheelSteer = steer;
#endif
}

void LCR_rendererDraw(void)
{
  LCR_LOG2("rendering frame (start)");

  // first make sure rotations are in correct range:
  LCR_renderer.scene.camera.transform.rotation.y = S3L_wrap(
    LCR_renderer.scene.camera.transform.rotation.y, S3L_F);

  LCR_renderer.scene.camera.transform.rotation.x = S3L_clamp(
    LCR_renderer.scene.camera.transform.rotation.x,-1 * S3L_F / 4,S3L_F / 4);

  LCR_renderer.previousTriID = -1;
  S3L_newFrame();
  
#if LCR_ANIMATE_CAR  
  _LCR_rendererAnimateCar();
#endif

  _LCR_rendererLoadMapChunks(); // TODO: call only once in a while?

  LCR_rendererDrawSky(1,
    LCR_renderer.scene.camera.transform.rotation.y,
    -4 * LCR_renderer.scene.camera.transform.rotation.x);

  LCR_drawLevelFloor();
  LCR_rendererDrawLOD();

  LCR_LOG2("gonna render 3D scene");
  S3L_drawScene(LCR_renderer.scene);
  LCR_LOG2("rendering 3D scene done");
 
  LCR_renderer.frame++;

  LCR_LOG2("rendering frame (end)");
}

#endif // guard