SPIRV-Cross/reference/shaders-msl/tese/triangle-tess-level.tese
Chip Davis f3c0942d10 MSL: Use vectors for the tessellation level builtins in tese shaders.
The tessellation levels in Metal are stored as a densely-packed array of
half-precision floating point values. But, stage-in attributes in Metal
have to have offsets and strides aligned to a multiple of four, so we
can't add them individually. Luckily for us, the arrays have lengths
less than 4. So, let's use vectors for them!

Triangles get a single attribute with a `float4`, where the outer levels
are in `.xyz` and the inner levels are in `.w`. The arrays are unpacked
as though we had added the elements individually. Quads get two: a
`float4` with the outer levels and a `float2` with the inner levels.
Further, since vectors can be indexed as arrays, there's no need to
unpack them in this case.

This also saves on precious vertex attributes. Before, we were using up
to 6 of them. Now we need two at most.
2019-02-22 12:18:51 -06:00

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878 B
GLSL

#include <metal_stdlib>
#include <simd/simd.h>
using namespace metal;
struct main0_out
{
float4 gl_Position [[position]];
};
struct main0_patchIn
{
float4 gl_TessLevel [[attribute(0)]];
};
[[ patch(triangle, 0) ]] vertex main0_out main0(main0_patchIn patchIn [[stage_in]], float3 gl_TessCoord [[position_in_patch]])
{
main0_out out = {};
float gl_TessLevelInner[2] = {};
float gl_TessLevelOuter[4] = {};
gl_TessLevelInner[0] = patchIn.gl_TessLevel.w;
gl_TessLevelOuter[0] = patchIn.gl_TessLevel.x;
gl_TessLevelOuter[1] = patchIn.gl_TessLevel.y;
gl_TessLevelOuter[2] = patchIn.gl_TessLevel.z;
out.gl_Position = float4((gl_TessCoord.x * gl_TessLevelInner[0]) * gl_TessLevelOuter[0], (gl_TessCoord.y * gl_TessLevelInner[0]) * gl_TessLevelOuter[1], (gl_TessCoord.z * gl_TessLevelInner[0]) * gl_TessLevelOuter[2], 1.0);
return out;
}