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Shader Linking
In order to pass data between the vertex and fragment shader, a sort of link-program seems to be copying from the output of the vertex shader into the TRAM (the RAM used as input to rasterization and shading).
This program is located at offset 0x300 and upwards, and consists of a 64-bit words. The first word contains the location to copy from, in the vertex shader export, the latter word contains the location in TRAM, interpolation parameters are mixed in.
| Bits | Meaning |
|---|---|
| 0..1 | VEC4 select: 0 = full VEC4 1 = VEC4.z (VEC4.x = VEC4.z) |
| 3..6 | Vertex import index |
| 9..14 | TRAM row number |
| 16 | TRAM.x is constant across width |
| 17 | TRAM.x is constant across length |
| 18..19 | TRAM.x across point ? |
| 20 | VEC4.y is constant across width |
| 21 | TRAM.y is constant across length |
| 22..23 | TRAM.y across point ? |
| 24 | TRAM.z is constant across width |
| 25 | TRAM.z is constant across length |
| 26..27 | TRAM.z across point ? |
| 28 | TRAM.w is constant across width |
| 29 | TRAM.w is constant across length |
| 30..31 | TRAM.w across point ? |
| Bits | Meaning |
|---|---|
| 0..1 | Import component swizzle to TRAM.x |
| 2..3 | TRAM.x destination type |
| 4..5 | Import component swizzle to TRAM.y |
| 6..7 | TRAM.y destination type |
| 8..9 | Import component swizzle to TRAM.z |
| 10..11 | TRAM.z destination type |
| 12..13 | Import component swizzle to TRAM.w |
| 14..15 | TRAM.w destination type |
| 16 | TRAM.x triangle interpolation disable |
| 17 | TRAM.y triangle interpolation disable |
| 18 | TRAM.z triangle interpolation disable |
| 19 | TRAM.w triangle interpolation disable |
| Value | Meaning |
|---|---|
| 0 | none/skip |
| 1 | fx10 low halve |
| 2 | fx10 high halve |
| 3 | fp20 |
| Value | Meaning |
|---|---|
| 0 | VEC4.x |
| 1 | VEC4.y |
| 2 | VEC4.z |
| 3 | VEC4.w |
Disabling triangle interpolation picks the value from the third vertex in if drawing triangles. This is what we want for triangle strips and triangle fans, but not normal triangles. Which means we'll probably need to use the "constant across length"-flag in that case.
Defines the number of used TRAM rows.
| Bits | Meaning |
|---|---|
| 8..14 | number of used TRAM rows |
| 0..6 | 64 / number of used TRAM rows |