Update

3d_model.md

@@ -229,7 +229,7 @@ OK, back to the mainstream now. Nowadays as a [FOSS](foss.md) user you will most
   - 3D rendering (and also modeling) works with the concept of a **[scene](scene.md)** in which a number of models reside, as well as a virtual camera (or multiple ones), lights and other objects. These objects have **transformations** (normally translation, rotation and scale, represented by [matrices](matrix.md)) and may form a hierarchy, so called [scene graph](scene_graph.md) (some objects may be parents of other objects, meaning the child transformations are relative to parents) etc.
   - A 3D renderer will draw the triangles the model consists of by applying **[shading](shading.md)** to determine color of each [pixel](pixel.md) of the [rasterized](rasterization.md) triangle. Shading takes into account besides others texture(s) of the model, its material properties and light falling on the model (in which the model normals play a big role). Shading can be modified by creating **[shaders](shader.md)** (if you don't create custom shaders, some default one will be used).
   - Briefly learn about other concepts such as low/high poly modeling and basic **3D formats** such as [OBJ](obj.md) and [COLLADA](collada.md) (which features they support etc.), possible other models representations ([voxels](voxel.md), [point clouds](point_cloud.md), ...) etc.
-2. **Manually create a few extremely simple [low-poly](low_poly.md) untextured models**, e.g. that of a simple house, laptop, hammer, bottle etc. Keep the vertex and triangle count very low (under 100), make the model by MANUALLY creating every vertex and triangle and focus only on learning this low level geometry manipulation well (how to create a vertex, how to split an edge, how to rotate a triangle, ...), making the model conform to good practice and get familiar with tools you're using, i.e. learn the key binds, locking movement direction to principal axes, learn manipulating your 3D view, setting up the free/side/front/top view with reference images etc. Make the model nice! I.e. make it have correctly facing triangles (turn [backface culling](backface_culling.md) on to check this), avoid intersecting triangles, unnecessary triangles and vertices, remove all duplicate vertices (don't have multiple vertices with the same position), connect all that should be connected, avoid badly shaped triangles (e.g. extremely acute/long ones) etc. Also learn about normals and make them nice! I.e. try automatic normal generation (fiddle e.g. with angle thresholds for sharp/smooth edges), see how they affect the model look, try manually marking some edges sharp, try out smoothing groups etc. Save your final models in OBJ format (one of the simplest and most common formats supporting all you need at this stage). All this will be a lot to learn, that's why you must not try to create a complex model at this stage. You can keep yourself "motivated" e.g. by aiming for creating a low-poly model collection you can share at opengameart or somewhere :)
+2. **Manually create a few extremely simple [low-poly](low_poly.md) untextured models**, e.g. that of a simple house, laptop, hammer, bottle etc. Keep the vertex and triangle count very low (under 100), make the model by MANUALLY creating every vertex and triangle and focus only on learning this low level geometry manipulation well (how to create a vertex, how to split an edge, how to rotate a triangle, ...), making the model conform to good practice and get familiar with tools you're using, i.e. learn the key binds, locking movement direction to principal axes, learn manipulating your 3D view, setting up the free/side/front/top view with reference images etc. Make the model nice! I.e. make it have correctly facing triangles (turn [backface culling](backface_culling.md) on to check this), avoid intersecting triangles, unnecessary triangles and vertices, remove all duplicate vertices (don't have multiple vertices with the same position), connect all that should be connected, avoid badly shaped triangles (e.g. extremely acute/long ones) etc. Keep the triangle count as low as possible, remember, **there always has to be a very good reason to add a triangle** -- there must be no triangle at all whose purpose is not justified, i.e. which is not absolutely necessary to achieve something about the model's look. If you can take the triangle away and still make the model look more or less the same, the triangle must be taken away. Also learn about normals and make them nice! I.e. try automatic normal generation (fiddle e.g. with angle thresholds for sharp/smooth edges), see how they affect the model look, try manually marking some edges sharp, try out smoothing groups etc. Save your final models in OBJ format (one of the simplest and most common formats supporting all you need at this stage). All this will be a lot to learn, that's why you must not try to create a complex model at this stage. You can keep yourself "motivated" e.g. by aiming for creating a low-poly model collection you can share at opengameart or somewhere :)
 3. **Learn texturing** -- just take the models you have and try to put a simple texture on them by drawing a simple image, then unwrapping the UV coordinates and MANUALLY editing the UV map to fit on the model. Again the goal is to get familiar with the tools and concepts now; experiment with helpers such as unwrapping by "projecting from 3D view", using "smart" UV unwrap etc. Make the UV map nice! Just as model geometry, UV maps also have good practice -- e.g. you should utilize as many texture pixels as possible (otherwise you're wasting space in the image), watch out for [color bleeding](color_bleeding.md), the mapping should have kind of "uniform pixel density" (or possibly increased density on triangles where more details is supposed to be), some pixels of the texture may be mapped to multiple triangles if possible (to efficiently utilize them) etc. Only make a simple diffuse texture (don't do [PBR](pbr.md), material textures etc., that's too advanced now). Try out texture painting and manual texture creation in a 2D image program, get familiar with both. 
 4. **Learn modifiers and advanced tools**. Modifiers help you e.g. with the creation of symmetric models: you only model one side and the other one gets mirrored. Subdivide modifier will automatically create a higher poly version of your model (but you need to help it by telling it which sides are sharp etc.). [Boolean](bool.md) operations allow you to apply set operations like unification or subtraction of shapes (but usually create a messy geometry you have to repair!). There are many tools, experiment and learn about their pros and cons, try to incorporate them to your modeling.
 5. **Learn retopology and possibly sculpting**. Topology is an extremely important concept -- it says what the structure of triangles/polygons is, how they are distributed, how they are connected, which curves their edges follow etc. Good topology has certain rules (e.g. ideally only being composed of quads, being denser where the shape has more detail and sparser where it's flat, having edges so that animation won't deform the model badly etc.). Topology is important for efficiency (you utilize your polygon budget well), texturing and especially animation (nice deformation of the model). Creating more complex models is almost always done in the following two steps: