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/*
See LICENSE folder for this sample’s licensing information.
Abstract:
Metal shaders used for this sample
*/
#include <metal_stdlib>
#include <simd/simd.h>
using namespace metal;
// Include header shared between this Metal shader code and C code executing Metal API commands
#import "AAPLShaderTypes.h"
// Vertex shader outputs and fragment shader inputs
typedef struct
{
// The [[position]] attribute of this member indicates that this value is the clip space
// position of the vertex when this structure is returned from the vertex function
float4 clipSpacePosition [[position]];
// Since this member does not have a special attribute, the rasterizer interpolates
// its value with the values of the other triangle vertices and then passes
// the interpolated value to the fragment shader for each fragment in the triangle
float4 color;
} RasterizerData;
// Vertex function
vertex RasterizerData
vertexShader(uint vertexID [[vertex_id]],
constant AAPLVertex *vertices [[buffer(AAPLVertexInputIndexVertices)]],
constant vector_uint2 *viewportSizePointer [[buffer(AAPLVertexInputIndexViewportSize)]])
{
RasterizerData out;
// Initialize our output clip space position
out.clipSpacePosition = vector_float4(0.0, 0.0, 0.0, 1.0);
// Index into our array of positions to get the current vertex
// Our positions are specified in pixel dimensions (i.e. a value of 100 is 100 pixels from
// the origin)
float2 pixelSpacePosition = vertices[vertexID].position.xy;
// Dereference viewportSizePointer and cast to float so we can do floating-point division
vector_float2 viewportSize = vector_float2(*viewportSizePointer);
// The output position of every vertex shader is in clip-space (also known as normalized device
// coordinate space, or NDC). A value of (-1.0, -1.0) in clip-space represents the
// lower-left corner of the viewport whereas (1.0, 1.0) represents the upper-right corner of
// the viewport.
// Calculate and write x and y values to our clip-space position. In order to convert from
// positions in pixel space to positions in clip-space, we divide the pixel coordinates by
// half the size of the viewport.
out.clipSpacePosition.xy = pixelSpacePosition / (viewportSize / 2.0);
// Pass our input color straight to our output color. This value will be interpolated
// with the other color values of the vertices that make up the triangle to produce
// the color value for each fragment in our fragment shader
out.color = vertices[vertexID].color;
return out;
}
// Fragment function
fragment float4 fragmentShader(RasterizerData in [[stage_in]])
{
// We return the color we just set which will be written to our color attachment.
return in.color;
}