SPIRV-Cross/reference/shaders-msl/frag/input-attachment-ms.frag
Chip Davis fd738e3387 MSL: Adjust FragCoord for sample-rate shading.
In Metal, the `[[position]]` input to a fragment shader remains at
fragment center, even at sample rate, like OpenGL and Direct3D. In
Vulkan, however, when the fragment shader runs at sample rate, the
`FragCoord` builtin moves to the sample position in the framebuffer,
instead of the fragment center. To account for this difference, adjust
the `FragCoord`, if present, by the sample position. The -0.5 offset is
because the fragment center is at (0.5, 0.5).

Also, add an option to force sample-rate shading in a fragment shader.
Since Metal has no explicit control for this, this is done by adding a
dummy `[[sample_id]]` which is otherwise unused, if none is already
present. This is intended to be used from e.g. MoltenVK when a
pipeline's `minSampleShading` value is nonzero.

Instead of checking if any `Input` variables have `Sample`
interpolation, I've elected to check that the `SampleRateShading`
capability is present. Since `SampleId`, `SamplePosition`, and the
`Sample` interpolation decoration require this cap, this should be
equivalent for any valid SPIR-V module. If this isn't acceptable, let me
know.
2020-11-23 10:30:24 -06:00

28 lines
893 B
GLSL

#pragma clang diagnostic ignored "-Wmissing-prototypes"
#include <metal_stdlib>
#include <simd/simd.h>
using namespace metal;
struct main0_out
{
float4 FragColor [[color(0)]];
};
static inline __attribute__((always_inline))
float4 load_subpasses(thread const texture2d_ms<float> uInput, thread uint& gl_SampleID, thread float4& gl_FragCoord)
{
float4 _24 = uInput.read(uint2(gl_FragCoord.xy), gl_SampleID);
return _24;
}
fragment main0_out main0(texture2d_ms<float> uSubpass0 [[texture(0)]], texture2d_ms<float> uSubpass1 [[texture(1)]], uint gl_SampleID [[sample_id]], float4 gl_FragCoord [[position]])
{
main0_out out = {};
gl_FragCoord.xy += get_sample_position(gl_SampleID) - 0.5;
out.FragColor = (uSubpass0.read(uint2(gl_FragCoord.xy), 1) + uSubpass1.read(uint2(gl_FragCoord.xy), 2)) + load_subpasses(uSubpass0, gl_SampleID, gl_FragCoord);
return out;
}