Use texture for clipping

CMakeLists.txt

@@ -23,4 +23,5 @@ add_subdirectory(ex5_aarect)
 add_subdirectory(ex6_mstxt)
 add_subdirectory(ex7_aarect2)
 add_subdirectory(ex8_clip)
-add_subdirectory(ex9_aaclip)
+add_subdirectory(ex9_aaclip)
+add_subdirectory(ex10_aaclip2)

ex10_aaclip2/CMakeLists.txt

@@ -0,0 +1,22 @@
+cmake_minimum_required(VERSION 3.13)
+project(aaclip2)
+
+set(CMAKE_CXX_STANDARD 17)
+
+add_executable(aaclip2 aaclip2.mm aaclip2.metal)
+
+target_link_libraries(aaclip2 ${APPKIT_LIBRARY})
+target_link_libraries(aaclip2 "-framework Cocoa")
+target_link_libraries(aaclip2 "-framework Metal")
+target_link_libraries(aaclip2 "-framework MetalKit")
+target_link_libraries(aaclip2 "-framework QuartzCore")
+
+add_custom_command(
+        OUTPUT ${PROJECT_BINARY_DIR}/aaclip2sh.metallib_
+        WORKING_DIR ${PROJECT_BINARY_DIR}
+        COMMAND ${METAL} -o aaclip2sh.air ${CMAKE_SOURCE_DIR}/ex10_aaclip2/aaclip2.metal
+        COMMAND ${METALLIB} -o aaclip2sh.metallib_ aaclip2sh.air
+        COMMAND ${CMAKE_COMMAND} -E copy aaclip2sh.metallib_ aaclip2sh.metallib
+        MAIN_DEPENDENCY aaclip2.metal
+        VERBATIM
+)

ex10_aaclip2/aaclip2.metal

@@ -0,0 +1,93 @@
+#include <simd/simd.h>
+#include "aaclip2.h"
+
+using namespace metal;
+
+struct VertexInput {
+    float3 position [[attribute(VertexAttributePosition)]];
+    half4 color [[attribute(VertexAttributeColor)]];
+};
+
+struct TxVertexInput {
+    float3 position [[attribute(VertexAttributePosition)]];
+    half4 color [[attribute(VertexAttributeColor)]];
+    float2 texCoords [[attribute(VertexAttributeTexPos)]];
+};
+
+struct ShaderInOut {
+    float4 position [[position]];
+    half4  color;
+};
+
+struct TxShaderInOut {
+    float4 position [[position]];
+    half4  color;
+    float2 texCoords [[attribute(VertexAttributeTexPos)]];
+};
+
+struct StencilShaderInOut {
+    float4 position [[position]];
+    char color;
+};
+
+vertex ShaderInOut vert(VertexInput in [[stage_in]],
+	   constant FrameUniforms& uniforms [[buffer(FrameUniformBuffer)]]) {
+    ShaderInOut out;
+    float4 pos4 = float4(in.position, 1.0);
+    out.position = uniforms.projectionViewModel * pos4;
+    out.color = in.color / 255.0;
+    return out;
+}
+
+vertex StencilShaderInOut vert_stencil(VertexInput in [[stage_in]],
+    constant FrameUniforms& uniforms [[buffer(FrameUniformBuffer)]]) {
+    StencilShaderInOut out;
+    float4 pos4 = float4(in.position, 1.0);
+    out.position = uniforms.projectionViewModel * pos4;
+    out.color = 0xFF;
+    return out;
+}
+
+fragment half4 frag(ShaderInOut in [[stage_in]]) {
+    return in.color;
+}
+
+fragment unsigned int frag_stencil(StencilShaderInOut in [[stage_in]]) {
+    return in.color;
+}
+
+vertex TxShaderInOut tx_vert(TxVertexInput in [[stage_in]],
+    constant FrameUniforms& uniforms [[buffer(FrameUniformBuffer)]]) {
+    TxShaderInOut out;
+    float4 pos4 = float4(in.position, 1.0);
+    out.position = uniforms.projectionViewModel * pos4;
+    out.color = in.color / 255.0;
+    out.texCoords = in.texCoords;
+    return out;
+}
+
+fragment half4 tx_frag(
+        TxShaderInOut vert  [[stage_in]],
+texture2d<float, access::sample> renderTexture [[texture(0)]],
+        texture2d<float, access::sample> stencilTexture [[texture(1)]]
+)
+{
+    constexpr sampler textureSampler (mag_filter::linear,
+                                  min_filter::linear);
+    float4 pixelColor = renderTexture.sample(textureSampler, vert.texCoords);
+    float4 stencil = stencilTexture.sample(textureSampler, vert.texCoords);
+    if (stencil.r ==  0.0 && stencil.g ==  0.0 && stencil.b ==  0.0 && stencil.a ==  0.0) {
+        discard_fragment();
+    }
+    return half4(pixelColor.r*pixelColor.a, pixelColor.g*pixelColor.a, pixelColor.b*pixelColor.a, 1.0);
+}
+
+kernel void stencil2tex(const device uchar *imageBuffer [[buffer(0)]],
+    device uchar4 *outputBuffer [[buffer(1)]],
+    uint gid [[thread_position_in_grid]])
+{
+    uchar p = imageBuffer[gid];
+    outputBuffer[gid] = uchar4(p, p, p, p);
+    //outputBuffer[gid] = uchar4(255, 255, 255, 255);
+
+}