Programming The Vertex Shader
This information is only for the ones of you who are interested and have a bit of programming experience as well as a minimal understanding of 3D math.
These are the instructions:
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| Instruction | Parameters | Action |
|---|---|---|
| nop | Row 0 - Cell 1 | do nothing |
| mov | dest, src | move |
| mul | dest, src1, rc2 | Set dest to the product of src1 and src2 |
| add | dest, src1, rc2 | Add src1 to src2. [And the optional negation creates subtraction] |
| mad | dest, src1, rc2, rc3 | Multiply src1 by src2 and add src3 - into dst |
| rsq | dest, src | Reciprocal square root of src (much more useful than straight 'square root').dest.x = dest.y = dest.z = dest.w = 1/sqrt(src) |
| dp3 | dest, src1, src2 | 3 Component dot product |
| dp4 | dest, src1, src2 | 4 Component dot product |
| dst | dest, src1, src2 | Calculate distance vector. src1 vector is (NA,d*d,d*d,NA) and src2 is (NA,1/d,NA,1/d).dest is set to (1,d,d*d,1/d) |
| lit | dest, src | Calculates lighting coefficients from two dot products and a power. src is:src.x = n o l (unit normal and light vectors)src.y = n o h (unit normal and halfangle vectors)src.z is unusedsrc.w = power (in range +128 to -128) |
| min | dest, src1, src2 | Component-wise min operation |
| max | dest, src1, src2 | Component-wise max operation |
| slt | dest, src1, src2 | dest = (src1 < src2) ? 1 : 0 |
| sge | dest, src1, src2 | dst = (src1 >= src2) ? 1 : 0 |
| expp | dest, src.w | dest.x = 2 ** (int)src.wdest.y = fractional part (src.w)dest.z = 2 ** src.wdest.w = 1.0 |
| log | dest, src.w | dest.x = exponent((int)src.w)dest.y = mantissa(src.w)dest.z = log2(src.w)dest.w = 1.0 |
| rcp | dest, src.w | dest.x = dest.y = dest.z = dest.w = 1 / src |
These few instructions are already quite powerful. To make the handling easier, NVIDIA added a few more features, 'costless' negation and swizzling...
