design.txt revision 3c827367444ee418f129b2c238299f49d3264554 
1Reference Renderer Design Notes
2-------------------------------
3
4Requirements:
5 - must support arbitrary VA arrays
6 - must support primitive setup reference
7 - must support lines, points
8 - must support instancing
9 - must support vertex shading -> custom position transformations
10 - flat, noperspective shading
11 - multiple render targets
12 - faster shading? move packet loop inside shader
13   (helper class can make shader implementation easier)
14 - can be extended for tessellation and geometry shading
15
16Integrate with:
17 - sglr
18 - random shader generator
19
20Uniforms:
21 - shader objects can contain parameters, renderer doesn't care about them
22 - can contain simple data or references to resources (textures for example)
23
24Pipeline:
25
26Vertex cache:
27 - based on indices setup transformed vertex buffer
28 - in:
29   + index list
30   + VS generic output count
31 - out:
32   + VS execution queue
33   + index remap information?
34 - trivial implementation:
35   + run VS for all vertices at once
36
37VertexShader:
38 - provides position & point size
39 - transforms other vertices
40 - in:
41   + VertexAttrib array
42   + packet list:
43     + VertexID, InstanceID (pack into some accessor?)
44   + uniform ptr
45 - out:
46   + position
47   + point size
48   + array of generic transformed attributes (float/int/uint)
49
50Tessellation:
51 - \todo [pyry] Define
52 - replaces primitive assembly?
53
54Primitive assembly:
55 - sets up primitives
56 - gl3: triangles, points, lines (adjecency?)
57 - in:
58   + full primitive type
59   + index list
60   + position & point size from VS
61 - out:
62   + primitive list for rasterization / geometry shading
63     + positions
64	 + provoking vertex for flatshading
65
66GeometryShader:
67 - in:
68   + primitive list
69 - out:
70   + changed primitive list
71
72Coordinate transform:
73 - in:
74   + primitive list
75 - out:
76   + coordinates after viewport transform
77   + z-clipping bits
78
79Rasterizer:
80 - pretty much as it is currently
81
82FragmentShader:
83 - in:
84   + packet list:
85     + base coordinates
86	 + barycentrics, both perspective and non-perspective
87	 + generic attribute accessor (2 or 3 vertices)
88	 + provoking vertex index
89   + uniform ptr
90 - out:
91   + shaded packet list:
92     + colors per render target
93	 + modified live mask - for discard
94 - utils:
95   + compute derivatives from data in SoA form
96   + compute lod for texturing
97