From c1fcd1a0c0b8cc79f1e921282876134ed67517ee Mon Sep 17 00:00:00 2001
From: Lior Halphon <LIJI32@gmail.com>
Date: Fri, 15 Jun 2018 13:58:50 +0300
Subject: [PATCH] Added frame blending

---
 Cocoa/GBViewMetal.m        | 21 +++++++++++++++++++++
 Shaders/MasterShader.metal |  7 ++++++-
 2 files changed, 27 insertions(+), 1 deletion(-)

diff --git a/Cocoa/GBViewMetal.m b/Cocoa/GBViewMetal.m
index 157ddf37..89534929 100644
--- a/Cocoa/GBViewMetal.m
+++ b/Cocoa/GBViewMetal.m
@@ -24,6 +24,7 @@ static const vector_float2 rect[] =
     id<MTLBuffer> vertices;
     id<MTLRenderPipelineState> pipeline_state;
     id<MTLCommandQueue> command_queue;
+    id<MTLBuffer> mix_previous_buffer;
 }
 
 - (void)createInternalView
@@ -46,6 +47,12 @@ static const vector_float2 rect[] =
                                    length:sizeof(rect)
                                   options:MTLResourceStorageModeShared];
 
+    
+    static const bool default_mix_value = false;
+    mix_previous_buffer = [device newBufferWithBytes:&default_mix_value
+                                              length:sizeof(default_mix_value)
+                                             options:MTLResourceStorageModeShared];
+    
     [self loadShader];
 }
 
@@ -93,12 +100,19 @@ static const vector_float2 rect[] =
                mipmapLevel:0
                  withBytes:[self currentBuffer]
                bytesPerRow:PITCH];
+    if ([self shouldBlendFrameWithPrevious]) {
+        [previous_texture replaceRegion:region
+                            mipmapLevel:0
+                              withBytes:[self previousBuffer]
+                            bytesPerRow:PITCH];
+    }
     
     MTLRenderPassDescriptor *render_pass_descriptor = view.currentRenderPassDescriptor;
     id<MTLCommandBuffer> command_buffer = [command_queue commandBuffer];
 
     if(render_pass_descriptor != nil)
     {
+        *(bool *)[mix_previous_buffer contents] = [self shouldBlendFrameWithPrevious];
         id<MTLRenderCommandEncoder> render_encoder =
             [command_buffer renderCommandEncoderWithDescriptor:render_pass_descriptor];
         
@@ -113,9 +127,16 @@ static const vector_float2 rect[] =
                                  offset:0
                                 atIndex:0];
         
+        [render_encoder setFragmentBuffer:mix_previous_buffer
+                                   offset:0
+                                  atIndex:0];
+        
         [render_encoder setFragmentTexture:texture
                                   atIndex:0];
         
+        [render_encoder setFragmentTexture:previous_texture
+                                   atIndex:1];
+        
         [render_encoder drawPrimitives:MTLPrimitiveTypeTriangleStrip
                           vertexStart:0
                           vertexCount:4];
diff --git a/Shaders/MasterShader.metal b/Shaders/MasterShader.metal
index a5157642..928c4c75 100644
--- a/Shaders/MasterShader.metal
+++ b/Shaders/MasterShader.metal
@@ -37,9 +37,14 @@ static inline float4 texture(texture2d<half> texture, float2 pos)
 }
 
 fragment float4 fragment_shader(rasterizer_data in [[stage_in]],
-                                texture2d<half> image [[ texture(0) ]])
+                                texture2d<half> image [[ texture(0) ]],
+                                texture2d<half> previous_image [[ texture(1) ]],
+                                constant bool *mix_previous [[ buffer(0) ]])
 {
     in.texcoords.y = 1 - in.texcoords.y;
+    if (*mix_previous) {
+        return mix(texture(image, in.texcoords), texture(previous_image, in.texcoords), 0.5);
+    }
     return texture(image, in.texcoords);
 }