Update

3d_rendering.md

@@ -102,7 +102,7 @@ TODO: VoxelQuest has some innovative voxel rendering, check it out (https://www.
 
 If you're a complete noob and are asking what the essence of 3D is or just how to render simple 3Dish pictures for your game without needing a [PhD](phd.md), here's the very basics. Yes, you can use some 3D engine such as [Godot](godot.md) that has all the 3D rendering preprogrammed, but you'll surrender to [bloat](bloat.md), you won't really know what's going on and your ability to tinker with the rendering or optimizing it will be basically zero... AND you'll miss on all the [fun](fun.md) :) So here we just foreshadow some concepts you should start with if you want to program your own 3D rendering.
 
-The absolute basic thing in 3D is probably **[perspective](perspective.md)**, or the concept which says that "things further away look smaller". This is basically the number one thing you need to know and with which you can make simple 3D pictures, even though there are many more effects and concepts that "make pictures look 3D" and which you can potentially study later (lighting, shadows, [focus and blur](depth_of_field.md), [stereoscopy](stereo.md), [parallax](parallax.md), visibility/obstruction etc.). { It's probably possible to make something akin "3D" even without perspective, just with [orthographic](ortho.md) projection, but that's just getting to details now. Let's just suppose we need perspective. ~drummyfish }
+The absolute basic thing in 3D is probably **[perspective](perspective.md)**, or the concept which says that "things further away look smaller". This is basically the number one thing you need to know and with which you can make simple 3D pictures, even though there are many more effects and concepts that "make pictures look 3D" and which you can potentially study later (lighting, shadows, [focus and blur](depth_of_field.md), [stereoscopy](stereo.md), [parallax](parallax.md), visibility/obstruction etc.). { It's probably possible to make something akin to "3D" even without perspective, just with [orthographic](ortho.md) projection, but that's just getting to details now. Let's just suppose we need perspective. ~drummyfish }
 
 If you don't have rotating camera and other fancy things, perspective is actually mathematically very simple, you basically just **divide the object's size by its distance from the viewer**, i.e. its Z coordinate (you may divide by some multiple of Z coordinate, e.g. by 2 * Z to get different [field of view](fov.md)) -- the further away it is, the bigger number its size gets divided by so the smaller it becomes. This "dividing by distance" ultimately applies to all distances, so in the end even the details on the object get scaled according to their individual distance, but as a first approximation you may just consider scaling objects as a whole. Just keep in mind you should only draw objects whose Z coordinate is above some threshold (usually called a *near plane*) so that you don't divide by 0! With this "dividing by distance" trick you can make an extremely simple "3Dish" renderer that just draws [sprites](sprite.md) on the screen and scales them according to the perspective rules (e.g. some space simulator where the sprites are balls representing planets). There is one more thing you'll need to handle: **[visibility](visibility.md)**, i.e. nearer objects have to cover the further away objects -- you can do this by simply [sorting](sorting.md) the objects by distance and drawing them back-to-front ([painter's algorithm](painters_algorithm.md)).