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3d_rendering.md
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You may have come here just to learn about the typical realtime 3D rendering used in today's [games](game.md) because aside from research and niche areas this kind of 3D is what we normally deal with in practice. This is what this section is about.
Nowadays "game 3D" means a [GPU](gpu.md) accelerated 3D [rasterization](rasterization.md) done with rendering [APIs](api.md) such as [OpenGL](opengl.md), [Vulkan](vulkan.md), [Direct3D](d3d.md) or [Metal](metal.md) (the last two being [proprietary](proprietary.md) and therefore [shit](shit.md)) and higher level engines above them, e.g. [Godot](godot.md), [OpenSceneGraph](osg.md) etc. The methods seem to be evolving to some kind of rasterization/[pathtracing](pathtracing.md) hybrid, but rasterization is still the basis.
These days "game 3D" means a [GPU](gpu.md) accelerated 3D [rasterization](rasterization.md) done with rendering [APIs](api.md) such as [OpenGL](opengl.md), [Vulkan](vulkan.md), [Direct3D](d3d.md) or [Metal](metal.md) (the last two being [proprietary](proprietary.md) and therefore [shit](shit.md)) and higher level engines above them, e.g. [Godot](godot.md), [OpenSceneGraph](osg.md) etc. The methods seem to be evolving to some kind of rasterization/[pathtracing](pathtracing.md) hybrid, but rasterization is still the basis.
This mainstream rendering uses an [object order](object_order.md) approach (it blits 3D objects onto the screen rather than determining each pixel's color separately) and works on the principle of **triangle rasterization**, i.e. 3D models are composed of triangles (or higher polygons which are however eventually broken down into triangles) and these triangles are projected onto the screen according to the position of the virtual camera and laws of [perspective](perspective.md). Projecting the triangles means finding the 2D screen coordinates of each of the triangle's three vertices -- once we have thee coordinates, we draw (rasterize) the triangle to the screen just as a "normal" 2D triangle (well, with some asterisks).
Furthermore things such as [z-buffering](z_buffer.md) (for determining correct overlap of triangles) and [double buffering](double_buffering.md) are used, which makes this approach very memory ([RAM](ram.md)/[VRAM](vram.md)) expensive -- of course mainstream computers have more than enough memory but smaller computers (e.g. [embedded](embedded.md)) may suffer and be unable to handle this kind of rendering. Thankfully it is possible to adapt and imitate this kind of rendering even on "small" computers -- even those that don't have a GPU, i.e. with pure [software rendering](sw_rendering.md). For this we e.g. replace z-buffering with [painter's algorithm](painters_algorithm.md) (triangle sorting), drop features like [perspective correction](perspective_correction.md), [MIP mapping](mip_mapping.md) etc. (of course quality of the output will go down).
Additionally things such as [z-buffering](z_buffer.md) (for determining correct overlap of triangles) and [double buffering](double_buffering.md) are used, which makes this approach very memory ([RAM](ram.md)/[VRAM](vram.md)) expensive -- of course mainstream computers have more than enough memory but smaller computers (e.g. [embedded](embedded.md)) may suffer and be unable to handle this kind of rendering. Thankfully it is possible to adapt and imitate this kind of rendering even on "small" computers -- even those that don't have a GPU, i.e. with pure [software rendering](sw_rendering.md). For this we e.g. replace z-buffering with [painter's algorithm](painters_algorithm.md) (triangle sorting), drop features like [perspective correction](perspective_correction.md), [MIP mapping](mip_mapping.md) etc. (of course quality of the output will go down).
Also additionally there's a lot of [bloat](bloat.md) added in such as complex [screen space](screen_space.md) shaders, [pathtracing](pathtracing.md) (popularly known as *raytracing*), [megatexturing](megatexturing.md), [shadow rendering](shadow.md), [postprocessing](postprocessing.md), [compute shaders](compute_shader.md) etc. This may make it difficult to get into "modern" 3D rendering. Remember to [keep it simple](kiss.md).