From BlenderWiki
About
Here I'm gathering some ideas for high level design of the render engine. What I'm discussing here is not very far from the existing code, but there are no clear separations between the various parts in the code. Shuffling things around a bit and making the interfaces and functionality of various modules clear should help bring out the design better and show how it can be extended.
Interfaces
This is an overview of some interfaces, very simplified to give an idea of what they do. In practice these would be bigger, but listing those things would obscure the intention.
Engine
render(scene, result)
This corresponds to the render API. This design is only about the Blender render engine, and in particular the part that does the actual rendering. Compositing, sequencer, fields, etc sit at a higher level and may call render(scene, result) repeatedly.
DataBase
camera geometry lights materials textures raytree pointclouds shadowbuffers ...
Result
layers passes pixels
Camera
pos, dir = sample(x, y) x, y = project(pos)
ShadeInput
material geom p, dp/dxyz view uv, duv/dxyz ..
ShadeOutput
mask passes col
Material
col = bxdf(di|sp|tr|em, dir) dir = bxdf_sample(di|sp|tr|em) shade(shi, shr)
Various types of these may be BlenderMaterial, NodeMaterial, SLMaterial. What the right interface is, that's still unclear to me, because of the passive materials vs. active shaders, so both interfaces are here now.
Integrator
Not sure how this fits yet, is for example z-buffering part of an integrator? That seems kind of strange, but on the other hand an mlt integrator may want to sample the camera and so have full control over which pixel gets written to when. Also closely related to how a material is defined.
Texture
col = sample(p, dp/dxyz)
Environment
col = sample(dir, ddir/dxyz)
Geometry
rasterize(buffer) shi = shi_from_raster(id) raytree_insert(raytree) shi = shi_from_ray(id) geom = split_dice()
Examples: MeshGeometry, StrandGeometry, VolumeGeometry.
Light
i = intensity(pos) lpos = sample()
RayTree
build(geomlist) id = intersect(ray)
PointCloud
build(geomlist) col = lookup(pos, nor)
This would be for AAO, SSS or other things that need it.
ShadowBuffer
build(geomlist) i = intensity(pos)
