SPIRV-Cross/shaders-msl/frag/sample-rate-frag-coord-sample-input.frag

#version 450

layout(set = 0, binding = 0) uniform sampler2DArray tex;

layout(location = 0) sample in float foo;
layout(location = 0) out vec4 FragColor;

void main()
{
	FragColor = texture(tex, vec3(gl_FragCoord.xy, foo));
}
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. 2020-11-20 21:41:46 +00:00			`#version 450`

			`layout(set = 0, binding = 0) uniform sampler2DArray tex;`

			`layout(location = 0) sample in float foo;`
			`layout(location = 0) out vec4 FragColor;`

			`void main()`
			`{`
			`FragColor = texture(tex, vec3(gl_FragCoord.xy, foo));`
			`}`