Implementar shader CRT con post-processing: migración completa GLSL a MSL

- Migrar shader CRT de GLSL a Metal Shading Language (MSL)
- Implementar renderizado de dos pasadas:
  * Paso 1: Renderizar escena a textura offscreen
  * Paso 2: Aplicar efecto CRT como post-procesamiento
- Añadir shaders CRT con scanlines, shadow mask y gamma correction
- Crear offscreen render target para renderizado intermedio
- Implementar fullscreen quad para post-procesamiento
- Configurar pipeline CRT con samplers linear y NEAREST
- Mantener compatibilidad con sprites multi-color existentes
- Resolución virtual CRT: 320x240 para apariencia retro auténtica

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <noreply@anthropic.com>

data/crtpi_240.glsl

@@ -0,0 +1,234 @@
+/*
+    crt-pi - A Raspberry Pi friendly CRT shader.
+
+    Copyright (C) 2015-2016 davej
+
+    This program is free software; you can redistribute it and/or modify it
+    under the terms of the GNU General Public License as published by the Free
+    Software Foundation; either version 2 of the License, or (at your option)
+    any later version.
+
+
+Notes:
+
+This shader is designed to work well on Raspberry Pi GPUs (i.e. 1080P @ 60Hz on a game with a 4:3 aspect ratio). It pushes the Pi's GPU hard and enabling some features will slow it down so that it is no longer able to match 1080P @ 60Hz. You will need to overclock your Pi to the fastest setting in raspi-config to get the best results from this shader: 'Pi2' for Pi2 and 'Turbo' for original Pi and Pi Zero. Note: Pi2s are slower at running the shader than other Pis, this seems to be down to Pi2s lower maximum memory speed. Pi2s don't quite manage 1080P @ 60Hz - they drop about 1 in 1000 frames. You probably won't notice this, but if you do, try enabling FAKE_GAMMA.
+
+SCANLINES enables scanlines. You'll almost certainly want to use it with MULTISAMPLE to reduce moire effects. SCANLINE_WEIGHT defines how wide scanlines are (it is an inverse value so a higher number = thinner lines). SCANLINE_GAP_BRIGHTNESS defines how dark the gaps between the scan lines are. Darker gaps between scan lines make moire effects more likely.
+
+GAMMA enables gamma correction using the values in INPUT_GAMMA and OUTPUT_GAMMA. FAKE_GAMMA causes it to ignore the values in INPUT_GAMMA and OUTPUT_GAMMA and approximate gamma correction in a way which is faster than true gamma whilst still looking better than having none. You must have GAMMA defined to enable FAKE_GAMMA.
+
+CURVATURE distorts the screen by CURVATURE_X and CURVATURE_Y. Curvature slows things down a lot.
+
+By default the shader uses linear blending horizontally. If you find this too blury, enable SHARPER.
+
+BLOOM_FACTOR controls the increase in width for bright scanlines.
+
+MASK_TYPE defines what, if any, shadow mask to use. MASK_BRIGHTNESS defines how much the mask type darkens the screen.
+
+*/
+
+#pragma parameter CURVATURE_X "Screen curvature - horizontal" 0.10 0.0 1.0 0.01
+#pragma parameter CURVATURE_Y "Screen curvature - vertical" 0.15 0.0 1.0 0.01
+#pragma parameter MASK_BRIGHTNESS "Mask brightness" 0.70 0.0 1.0 0.01
+#pragma parameter SCANLINE_WEIGHT "Scanline weight" 6.0 0.0 15.0 0.1
+#pragma parameter SCANLINE_GAP_BRIGHTNESS "Scanline gap brightness" 0.12 0.0 1.0 0.01
+#pragma parameter BLOOM_FACTOR "Bloom factor" 1.5 0.0 5.0 0.01
+#pragma parameter INPUT_GAMMA "Input gamma" 2.4 0.0 5.0 0.01
+#pragma parameter OUTPUT_GAMMA "Output gamma" 2.2 0.0 5.0 0.01
+
+// Haven't put these as parameters as it would slow the code down.
+#define SCANLINES
+#define MULTISAMPLE
+#define GAMMA
+//#define FAKE_GAMMA
+//#define CURVATURE
+//#define SHARPER
+// MASK_TYPE: 0 = none, 1 = green/magenta, 2 = trinitron(ish)
+#define MASK_TYPE 2
+
+
+#ifdef GL_ES
+#define COMPAT_PRECISION mediump
+precision mediump float;
+#else
+#define COMPAT_PRECISION
+#endif
+
+#ifdef PARAMETER_UNIFORM
+uniform COMPAT_PRECISION float CURVATURE_X;
+uniform COMPAT_PRECISION float CURVATURE_Y;
+uniform COMPAT_PRECISION float MASK_BRIGHTNESS;
+uniform COMPAT_PRECISION float SCANLINE_WEIGHT;
+uniform COMPAT_PRECISION float SCANLINE_GAP_BRIGHTNESS;
+uniform COMPAT_PRECISION float BLOOM_FACTOR;
+uniform COMPAT_PRECISION float INPUT_GAMMA;
+uniform COMPAT_PRECISION float OUTPUT_GAMMA;
+#else
+#define CURVATURE_X 0.05
+#define CURVATURE_Y 0.1
+#define MASK_BRIGHTNESS 0.80
+#define SCANLINE_WEIGHT 6.0
+#define SCANLINE_GAP_BRIGHTNESS 0.12
+#define BLOOM_FACTOR 3.5
+#define INPUT_GAMMA 2.4
+#define OUTPUT_GAMMA 2.2
+#endif
+
+/* COMPATIBILITY
+   - GLSL compilers
+*/
+
+//uniform vec2 TextureSize;
+#if defined(CURVATURE)
+varying vec2 screenScale;
+#endif
+varying vec2 TEX0;
+varying float filterWidth;
+
+#if defined(VERTEX)
+//uniform mat4 MVPMatrix;
+//attribute vec4 VertexCoord;
+//attribute vec2 TexCoord;
+//uniform vec2 InputSize;
+//uniform vec2 OutputSize;
+
+void main()
+{
+#if defined(CURVATURE)
+	screenScale = vec2(1.0, 1.0); //TextureSize / InputSize;
+#endif
+	filterWidth = (768.0 / 240.0) / 3.0;
+	TEX0 = vec2(gl_MultiTexCoord0.x, 1.0-gl_MultiTexCoord0.y)*1.0001;
+	gl_Position = gl_ModelViewProjectionMatrix * gl_Vertex;
+}
+#elif defined(FRAGMENT)
+
+uniform sampler2D Texture;
+
+#if defined(CURVATURE)
+vec2 Distort(vec2 coord)
+{
+	vec2 CURVATURE_DISTORTION = vec2(CURVATURE_X, CURVATURE_Y);
+	// Barrel distortion shrinks the display area a bit, this will allow us to counteract that.
+	vec2 barrelScale = 1.0 - (0.23 * CURVATURE_DISTORTION);
+	coord *= screenScale;
+	coord -= vec2(0.5);
+	float rsq = coord.x * coord.x + coord.y * coord.y;
+	coord += coord * (CURVATURE_DISTORTION * rsq);
+	coord *= barrelScale;
+	if (abs(coord.x) >= 0.5 || abs(coord.y) >= 0.5)
+		coord = vec2(-1.0);		// If out of bounds, return an invalid value.
+	else
+	{
+		coord += vec2(0.5);
+		coord /= screenScale;
+	}
+
+	return coord;
+}
+#endif
+
+float CalcScanLineWeight(float dist)
+{
+	return max(1.0-dist*dist*SCANLINE_WEIGHT, SCANLINE_GAP_BRIGHTNESS);
+}
+
+float CalcScanLine(float dy)
+{
+	float scanLineWeight = CalcScanLineWeight(dy);
+#if defined(MULTISAMPLE)
+	scanLineWeight += CalcScanLineWeight(dy-filterWidth);
+	scanLineWeight += CalcScanLineWeight(dy+filterWidth);
+	scanLineWeight *= 0.3333333;
+#endif
+	return scanLineWeight;
+}
+
+void main()
+{
+	vec2 TextureSize = vec2(320.0, 240.0);
+#if defined(CURVATURE)
+	vec2 texcoord = Distort(TEX0);
+	if (texcoord.x < 0.0)
+		gl_FragColor = vec4(0.0);
+	else
+#else
+	vec2 texcoord = TEX0;
+#endif
+	{
+		vec2 texcoordInPixels = texcoord * TextureSize;
+#if defined(SHARPER)
+		vec2 tempCoord = floor(texcoordInPixels) + 0.5;
+		vec2 coord = tempCoord / TextureSize;
+		vec2 deltas = texcoordInPixels - tempCoord;
+		float scanLineWeight = CalcScanLine(deltas.y);
+		vec2 signs = sign(deltas);
+		deltas.x *= 2.0;
+		deltas = deltas * deltas;
+		deltas.y = deltas.y * deltas.y;
+		deltas.x *= 0.5;
+		deltas.y *= 8.0;
+		deltas /= TextureSize;
+		deltas *= signs;
+		vec2 tc = coord + deltas;
+#else
+		float tempY = floor(texcoordInPixels.y) + 0.5;
+		float yCoord = tempY / TextureSize.y;
+		float dy = texcoordInPixels.y - tempY;
+		float scanLineWeight = CalcScanLine(dy);
+		float signY = sign(dy);
+		dy = dy * dy;
+		dy = dy * dy;
+		dy *= 8.0;
+		dy /= TextureSize.y;
+		dy *= signY;
+		vec2 tc = vec2(texcoord.x, yCoord + dy);
+#endif
+
+		vec3 colour = texture2D(Texture, tc).rgb;
+
+#if defined(SCANLINES)
+#if defined(GAMMA)
+#if defined(FAKE_GAMMA)
+		colour = colour * colour;
+#else
+		colour = pow(colour, vec3(INPUT_GAMMA));
+#endif
+#endif
+		scanLineWeight *= BLOOM_FACTOR;
+		colour *= scanLineWeight;
+
+#if defined(GAMMA)
+#if defined(FAKE_GAMMA)
+		colour = sqrt(colour);
+#else
+		colour = pow(colour, vec3(1.0/OUTPUT_GAMMA));
+#endif
+#endif
+#endif
+#if MASK_TYPE == 0
+		gl_FragColor = vec4(colour, 1.0);
+#else
+#if MASK_TYPE == 1
+		float whichMask = fract((gl_FragCoord.x*1.0001) * 0.5);
+		vec3 mask;
+		if (whichMask < 0.5)
+			mask = vec3(MASK_BRIGHTNESS, 1.0, MASK_BRIGHTNESS);
+		else
+			mask = vec3(1.0, MASK_BRIGHTNESS, 1.0);
+#elif MASK_TYPE == 2
+		float whichMask = fract((gl_FragCoord.x*1.0001) * 0.3333333);
+		vec3 mask = vec3(MASK_BRIGHTNESS, MASK_BRIGHTNESS, MASK_BRIGHTNESS);
+		if (whichMask < 0.3333333)
+			mask.x = 1.0;
+		else if (whichMask < 0.6666666)
+			mask.y = 1.0;
+		else
+			mask.z = 1.0;
+#endif
+
+		gl_FragColor = vec4(colour * mask, 1.0);
+#endif
+	}
+}
+#endif

source/main.cpp

@@ -38,6 +38,7 @@
 // Estructura para vértices de sprites
 struct SpriteVertex {
     float position[2];  // x, y coordinates
+    float color[4];     // r, g, b, a color components
     float texCoord[2];  // u, v texture coordinates
 };
 
@@ -204,24 +205,27 @@ fragment float4 triangle_fragment_main(VertexOut in [[stage_in]]) {
 }
 )";
 
-    // Shaders para sprites con textura
+    // Shaders para sprites con textura y color
     NSString* spriteVertexShaderSource = @R"(
 #include <metal_stdlib>
 using namespace metal;
 
 struct SpriteVertexIn {
     float2 position [[attribute(0)]];
-    float2 texCoord [[attribute(1)]];
+    float4 color [[attribute(1)]];
+    float2 texCoord [[attribute(2)]];
 };
 
 struct SpriteVertexOut {
     float4 position [[position]];
+    float4 color;
     float2 texCoord;
 };
 
 vertex SpriteVertexOut sprite_vertex_main(SpriteVertexIn in [[stage_in]]) {
     SpriteVertexOut out;
     out.position = float4(in.position, 0.0, 1.0);
+    out.color = in.color;
     out.texCoord = in.texCoord;
     return out;
 }
@@ -233,6 +237,7 @@ using namespace metal;
 
 struct SpriteVertexOut {
     float4 position [[position]];
+    float4 color;
     float2 texCoord;
 };
 
@@ -240,12 +245,205 @@ fragment float4 sprite_fragment_main(SpriteVertexOut in [[stage_in]],
                                    texture2d<float> spriteTexture [[texture(0)]],
                                    sampler textureSampler [[sampler(0)]]) {
     float4 textureColor = spriteTexture.sample(textureSampler, in.texCoord);
-    return textureColor;
+    return textureColor * in.color;  // Multiplicar textura por color de vértice para tinting
 }
 )";
 
-    // Compilar shaders de fondo
+    // Shaders para CRT post-processing (fullscreen quad)
+    NSString* crtVertexShaderSource = @R"(
+#include <metal_stdlib>
+using namespace metal;
+
+struct CRTVertexOut {
+    float4 position [[position]];
+    float2 texCoord;
+};
+
+vertex CRTVertexOut crt_vertex_main(uint vertexID [[vertex_id]]) {
+    CRTVertexOut out;
+
+    // Fullscreen quad con coordenadas de textura
+    float2 positions[6] = {
+        float2(-1.0, -1.0),  // Bottom left
+        float2( 1.0, -1.0),  // Bottom right
+        float2(-1.0,  1.0),  // Top left
+        float2( 1.0, -1.0),  // Bottom right
+        float2( 1.0,  1.0),  // Top right
+        float2(-1.0,  1.0)   // Top left
+    };
+
+    float2 texCoords[6] = {
+        float2(0.0, 1.0),    // Bottom left
+        float2(1.0, 1.0),    // Bottom right
+        float2(0.0, 0.0),    // Top left
+        float2(1.0, 1.0),    // Bottom right
+        float2(1.0, 0.0),    // Top right
+        float2(0.0, 0.0)     // Top left
+    };
+
+    out.position = float4(positions[vertexID], 0.0, 1.0);
+    out.texCoord = texCoords[vertexID];
+
+    return out;
+}
+)";
+
+    // CRT Fragment Shader - Migrado de GLSL a MSL
+    NSString* crtFragmentShaderSource = @R"(
+#include <metal_stdlib>
+using namespace metal;
+
+// Parámetros del CRT shader
+#define CURVATURE_X 0.05
+#define CURVATURE_Y 0.1
+#define MASK_BRIGHTNESS 0.80
+#define SCANLINE_WEIGHT 6.0
+#define SCANLINE_GAP_BRIGHTNESS 0.12
+#define BLOOM_FACTOR 3.5
+#define INPUT_GAMMA 2.4
+#define OUTPUT_GAMMA 2.2
+
+// Features habilitadas
+#define SCANLINES
+#define MULTISAMPLE
+#define GAMMA
+// #define FAKE_GAMMA
+// #define CURVATURE
+// #define SHARPER
+#define MASK_TYPE 2
+
+struct CRTVertexOut {
+    float4 position [[position]];
+    float2 texCoord;
+};
+
+float CalcScanLineWeight(float dist) {
+    return max(1.0 - dist * dist * SCANLINE_WEIGHT, SCANLINE_GAP_BRIGHTNESS);
+}
+
+float CalcScanLine(float dy, float filterWidth) {
+    float scanLineWeight = CalcScanLineWeight(dy);
+#ifdef MULTISAMPLE
+    scanLineWeight += CalcScanLineWeight(dy - filterWidth);
+    scanLineWeight += CalcScanLineWeight(dy + filterWidth);
+    scanLineWeight *= 0.3333333;
+#endif
+    return scanLineWeight;
+}
+
+fragment float4 crt_fragment_main(CRTVertexOut in [[stage_in]],
+                                texture2d<float> sceneTexture [[texture(0)]],
+                                sampler sceneSampler [[sampler(0)]]) {
+    float2 TextureSize = float2(320.0, 240.0);  // Resolución virtual del CRT
+    float filterWidth = (768.0 / 240.0) / 3.0;
+
+    float2 texcoord = in.texCoord;
+
+    // Convertir a píxeles
+    float2 texcoordInPixels = texcoord * TextureSize;
+
+#ifdef SHARPER
+    float2 tempCoord = floor(texcoordInPixels) + 0.5;
+    float2 coord = tempCoord / TextureSize;
+    float2 deltas = texcoordInPixels - tempCoord;
+    float scanLineWeight = CalcScanLine(deltas.y, filterWidth);
+    float2 signs = sign(deltas);
+    deltas.x *= 2.0;
+    deltas = deltas * deltas;
+    deltas.y = deltas.y * deltas.y;
+    deltas.x *= 0.5;
+    deltas.y *= 8.0;
+    deltas /= TextureSize;
+    deltas *= signs;
+    float2 tc = coord + deltas;
+#else
+    float tempY = floor(texcoordInPixels.y) + 0.5;
+    float yCoord = tempY / TextureSize.y;
+    float dy = texcoordInPixels.y - tempY;
+    float scanLineWeight = CalcScanLine(dy, filterWidth);
+    float signY = sign(dy);
+    dy = dy * dy;
+    dy = dy * dy;
+    dy *= 8.0;
+    dy /= TextureSize.y;
+    dy *= signY;
+    float2 tc = float2(texcoord.x, yCoord + dy);
+#endif
+
+    // Samplear la textura de escena
+    float3 colour = sceneTexture.sample(sceneSampler, tc).rgb;
+
+#ifdef SCANLINES
+#ifdef GAMMA
+#ifdef FAKE_GAMMA
+    colour = colour * colour;
+#else
+    colour = pow(colour, float3(INPUT_GAMMA));
+#endif
+#endif
+    scanLineWeight *= BLOOM_FACTOR;
+    colour *= scanLineWeight;
+
+#ifdef GAMMA
+#ifdef FAKE_GAMMA
+    colour = sqrt(colour);
+#else
+    colour = pow(colour, float3(1.0 / OUTPUT_GAMMA));
+#endif
+#endif
+#endif
+
+    // Shadow mask
+#if MASK_TYPE == 0
+    return float4(colour, 1.0);
+#else
+#if MASK_TYPE == 1
+    float whichMask = fract((in.position.x * 1.0001) * 0.5);
+    float3 mask;
+    if (whichMask < 0.5) {
+        mask = float3(MASK_BRIGHTNESS, 1.0, MASK_BRIGHTNESS);
+    } else {
+        mask = float3(1.0, MASK_BRIGHTNESS, 1.0);
+    }
+#elif MASK_TYPE == 2
+    float whichMask = fract((in.position.x * 1.0001) * 0.3333333);
+    float3 mask = float3(MASK_BRIGHTNESS, MASK_BRIGHTNESS, MASK_BRIGHTNESS);
+    if (whichMask < 0.3333333) {
+        mask.x = 1.0;
+    } else if (whichMask < 0.6666666) {
+        mask.y = 1.0;
+    } else {
+        mask.z = 1.0;
+    }
+#endif
+
+    return float4(colour * mask, 1.0);
+#endif
+}
+)";
+
+    // Compilar shaders CRT
     NSError* error = nil;
+    id<MTLLibrary> crtVertexLibrary = [device newLibraryWithSource:crtVertexShaderSource options:nil error:&error];
+    if (!crtVertexLibrary || error) {
+        if (error) {
+            std::cout << "Failed to compile CRT vertex shader: " << [[error localizedDescription] UTF8String] << std::endl;
+        }
+        return -1;
+    }
+
+    id<MTLLibrary> crtFragmentLibrary = [device newLibraryWithSource:crtFragmentShaderSource options:nil error:&error];
+    if (!crtFragmentLibrary || error) {
+        if (error) {
+            std::cout << "Failed to compile CRT fragment shader: " << [[error localizedDescription] UTF8String] << std::endl;
+        }
+        return -1;
+    }
+
+    id<MTLFunction> crtVertexFunction = [crtVertexLibrary newFunctionWithName:@"crt_vertex_main"];
+    id<MTLFunction> crtFragmentFunction = [crtFragmentLibrary newFunctionWithName:@"crt_fragment_main"];
+
+    // Compilar shaders de fondo
     id<MTLLibrary> backgroundVertexLibrary = [device newLibraryWithSource:backgroundVertexShaderSource options:nil error:&error];
     if (!backgroundVertexLibrary || error) {
         if (error) {
@@ -348,14 +546,17 @@ fragment float4 sprite_fragment_main(SpriteVertexOut in [[stage_in]],
     spritePipelineDescriptor.colorAttachments[0].destinationRGBBlendFactor = MTLBlendFactorOneMinusSourceAlpha;
     spritePipelineDescriptor.colorAttachments[0].destinationAlphaBlendFactor = MTLBlendFactorOneMinusSourceAlpha;
 
-    // Configurar vertex descriptor para sprites
+    // Configurar vertex descriptor para sprites (position + color + texCoord)
     MTLVertexDescriptor* spriteVertexDescriptor = [[MTLVertexDescriptor alloc] init];
     spriteVertexDescriptor.attributes[0].format = MTLVertexFormatFloat2;  // position
     spriteVertexDescriptor.attributes[0].offset = 0;
     spriteVertexDescriptor.attributes[0].bufferIndex = 0;
-    spriteVertexDescriptor.attributes[1].format = MTLVertexFormatFloat2;  // texCoord
+    spriteVertexDescriptor.attributes[1].format = MTLVertexFormatFloat4;  // color
     spriteVertexDescriptor.attributes[1].offset = 8;
     spriteVertexDescriptor.attributes[1].bufferIndex = 0;
+    spriteVertexDescriptor.attributes[2].format = MTLVertexFormatFloat2;  // texCoord
+    spriteVertexDescriptor.attributes[2].offset = 24;
+    spriteVertexDescriptor.attributes[2].bufferIndex = 0;
     spriteVertexDescriptor.layouts[0].stride = sizeof(SpriteVertex);
     spriteVertexDescriptor.layouts[0].stepFunction = MTLVertexStepFunctionPerVertex;
 
@@ -417,15 +618,57 @@ fragment float4 sprite_fragment_main(SpriteVertexOut in [[stage_in]],
         return -1;
     }
 
-    // Crear vertex buffer para sprites
+    // Crear vertex buffer para sprites (para 5 sprites = 30 vértices)
-    id<MTLBuffer> spriteVertexBuffer = [device newBufferWithLength:1024 options:MTLResourceCPUCacheModeDefaultCache];
+    id<MTLBuffer> spriteVertexBuffer = [device newBufferWithLength:4096 options:MTLResourceCPUCacheModeDefaultCache];
     if (!spriteVertexBuffer) {
         std::cout << "Failed to create sprite vertex buffer" << std::endl;
         return -1;
     }
 
-    std::cout << "Metal pipelines created successfully (background + triangle + sprites)" << std::endl;
+    // Crear offscreen render target para CRT post-processing
+    CGSize drawableSize = metalLayer.drawableSize;
+    MTLTextureDescriptor* offscreenTextureDescriptor = [MTLTextureDescriptor texture2DDescriptorWithPixelFormat:MTLPixelFormatBGRA8Unorm
+                                                                                                             width:(NSUInteger)drawableSize.width
+                                                                                                            height:(NSUInteger)drawableSize.height
+                                                                                                         mipmapped:NO];
+    offscreenTextureDescriptor.usage = MTLTextureUsageRenderTarget | MTLTextureUsageShaderRead;
+
+    id<MTLTexture> offscreenTexture = [device newTextureWithDescriptor:offscreenTextureDescriptor];
+    if (!offscreenTexture) {
+        std::cout << "Failed to create offscreen render target" << std::endl;
+        return -1;
+    }
+
+    // Crear pipeline CRT post-processing
+    MTLRenderPipelineDescriptor* crtPipelineDescriptor = [[MTLRenderPipelineDescriptor alloc] init];
+    crtPipelineDescriptor.vertexFunction = crtVertexFunction;
+    crtPipelineDescriptor.fragmentFunction = crtFragmentFunction;
+    crtPipelineDescriptor.colorAttachments[0].pixelFormat = metalLayer.pixelFormat;
+
+    id<MTLRenderPipelineState> crtPipelineState = [device newRenderPipelineStateWithDescriptor:crtPipelineDescriptor error:&error];
+    if (!crtPipelineState || error) {
+        if (error) {
+            std::cout << "Failed to create CRT render pipeline: " << [[error localizedDescription] UTF8String] << std::endl;
+        }
+        return -1;
+    }
+
+    // Crear sampler para CRT (linear para suavizar la escalada)
+    MTLSamplerDescriptor* crtSamplerDescriptor = [[MTLSamplerDescriptor alloc] init];
+    crtSamplerDescriptor.minFilter = MTLSamplerMinMagFilterLinear;
+    crtSamplerDescriptor.magFilter = MTLSamplerMinMagFilterLinear;
+    crtSamplerDescriptor.sAddressMode = MTLSamplerAddressModeClampToEdge;
+    crtSamplerDescriptor.tAddressMode = MTLSamplerAddressModeClampToEdge;
+
+    id<MTLSamplerState> crtSampler = [device newSamplerStateWithDescriptor:crtSamplerDescriptor];
+    if (!crtSampler) {
+        std::cout << "Failed to create CRT sampler" << std::endl;
+        return -1;
+    }
+
+    std::cout << "Metal pipelines created successfully (background + triangle + sprites + CRT)" << std::endl;
     std::cout << "Sprite texture loaded: " << [bitmap pixelsWide] << "x" << [bitmap pixelsHigh] << std::endl;
+    std::cout << "Offscreen render target created: " << (int)drawableSize.width << "x" << (int)drawableSize.height << std::endl;
 
     // Main loop
     bool quit = false;
@@ -444,12 +687,12 @@ fragment float4 sprite_fragment_main(SpriteVertexOut in [[stage_in]],
             continue;
         }
 
-        // Crear render pass descriptor
+        // PASO 1: Renderizar escena a offscreen texture
-        MTLRenderPassDescriptor* renderPassDescriptor = [MTLRenderPassDescriptor renderPassDescriptor];
+        MTLRenderPassDescriptor* offscreenRenderPassDescriptor = [MTLRenderPassDescriptor renderPassDescriptor];
-        renderPassDescriptor.colorAttachments[0].texture = drawable.texture;
+        offscreenRenderPassDescriptor.colorAttachments[0].texture = offscreenTexture;
-        renderPassDescriptor.colorAttachments[0].loadAction = MTLLoadActionClear;
+        offscreenRenderPassDescriptor.colorAttachments[0].loadAction = MTLLoadActionClear;
-        renderPassDescriptor.colorAttachments[0].clearColor = MTLClearColorMake(0.0, 0.0, 0.0, 1.0);
+        offscreenRenderPassDescriptor.colorAttachments[0].clearColor = MTLClearColorMake(0.0, 0.0, 0.0, 1.0);
-        renderPassDescriptor.colorAttachments[0].storeAction = MTLStoreActionStore;
+        offscreenRenderPassDescriptor.colorAttachments[0].storeAction = MTLStoreActionStore;
 
         // Crear command buffer
         id<MTLCommandBuffer> commandBuffer = [commandQueue commandBuffer];
@@ -457,58 +700,104 @@ fragment float4 sprite_fragment_main(SpriteVertexOut in [[stage_in]],
             continue;
         }
 
-        // Crear render command encoder
+        // Crear render command encoder para offscreen
-        id<MTLRenderCommandEncoder> renderEncoder = [commandBuffer renderCommandEncoderWithDescriptor:renderPassDescriptor];
+        id<MTLRenderCommandEncoder> offscreenEncoder = [commandBuffer renderCommandEncoderWithDescriptor:offscreenRenderPassDescriptor];
-        if (!renderEncoder) {
+        if (!offscreenEncoder) {
             continue;
         }
 
         // 1. Dibujar fondo degradado primero
-        [renderEncoder setRenderPipelineState:backgroundPipelineState];
+        [offscreenEncoder setRenderPipelineState:backgroundPipelineState];
-        [renderEncoder drawPrimitives:MTLPrimitiveTypeTriangle vertexStart:0 vertexCount:6];
+        [offscreenEncoder drawPrimitives:MTLPrimitiveTypeTriangle vertexStart:0 vertexCount:6];
 
         // 2. Dibujar triángulo encima
-        [renderEncoder setRenderPipelineState:trianglePipelineState];
+        [offscreenEncoder setRenderPipelineState:trianglePipelineState];
-        [renderEncoder drawPrimitives:MTLPrimitiveTypeTriangle vertexStart:0 vertexCount:3];
+        [offscreenEncoder drawPrimitives:MTLPrimitiveTypeTriangle vertexStart:0 vertexCount:3];
 
-        // 3. Dibujar sprite con alpha blending
+        // 3. Dibujar 5 sprites con diferentes colores
-        [renderEncoder setRenderPipelineState:spritePipelineState];
+        [offscreenEncoder setRenderPipelineState:spritePipelineState];
 
-        // Configurar textura y sampler
+        // Configurar textura y sampler para sprites
-        [renderEncoder setFragmentTexture:spriteTexture atIndex:0];
+        [offscreenEncoder setFragmentTexture:spriteTexture atIndex:0];
-        [renderEncoder setFragmentSamplerState:textureSampler atIndex:0];
+        [offscreenEncoder setFragmentSamplerState:textureSampler atIndex:0];
 
-        // Crear sprite centrado con un tamaño pequeño
+        // Crear 5 sprites en diferentes posiciones con diferentes colores
-        SpriteVertex spriteVertices[6];  // 2 triángulos para formar un quad
+        SpriteVertex spriteVertices[30];  // 5 sprites × 6 vértices cada uno
 
-        // Sprite centrado de 30x30 pixels en pantalla de 960x720 (mantiene proporción de 10px en 320x240)
+        // Configuración común
         float spriteSize = 30.0f;
         float windowWidth = 960.0f;
         float windowHeight = 720.0f;
+        float halfWidth = (spriteSize / windowWidth);
+        float halfHeight = (spriteSize / windowHeight);
 
-        // Convertir a coordenadas NDC
+        // Posiciones de los 5 sprites (evitando el centro donde está el triángulo)
-        float halfWidth = (spriteSize / windowWidth);   // 0.1 en NDC
+        float positions[5][2] = {
-        float halfHeight = (spriteSize / windowHeight); // 0.133 en NDC
+            {-0.6f,  0.6f},  // Esquina superior izquierda
+            { 0.6f,  0.6f},  // Esquina superior derecha
+            {-0.6f, -0.6f},  // Esquina inferior izquierda
+            { 0.6f, -0.6f},  // Esquina inferior derecha
+            { 0.0f, -0.8f}   // Centro inferior
+        };
+
+        // Colores para cada sprite (RGBA)
+        float colors[5][4] = {
+            {1.0f, 0.0f, 0.0f, 1.0f},  // Rojo
+            {0.0f, 1.0f, 0.0f, 1.0f},  // Verde
+            {0.0f, 0.0f, 1.0f, 1.0f},  // Azul
+            {1.0f, 1.0f, 0.0f, 1.0f},  // Amarillo
+            {1.0f, 0.0f, 1.0f, 1.0f}   // Magenta
+        };
+
+        // Generar vértices para los 5 sprites
+        for (int i = 0; i < 5; i++) {
+            float centerX = positions[i][0];
+            float centerY = positions[i][1];
+
+            // Índice base para este sprite
+            int baseIndex = i * 6;
 
             // Primer triángulo (bottom-left, bottom-right, top-left)
-        spriteVertices[0] = {{-halfWidth, -halfHeight}, {0.0f, 1.0f}}; // bottom-left
+            spriteVertices[baseIndex + 0] = {{centerX - halfWidth, centerY - halfHeight}, {colors[i][0], colors[i][1], colors[i][2], colors[i][3]}, {0.0f, 1.0f}};
-        spriteVertices[1] = {{ halfWidth, -halfHeight}, {1.0f, 1.0f}}; // bottom-right
+            spriteVertices[baseIndex + 1] = {{centerX + halfWidth, centerY - halfHeight}, {colors[i][0], colors[i][1], colors[i][2], colors[i][3]}, {1.0f, 1.0f}};
-        spriteVertices[2] = {{-halfWidth,  halfHeight}, {0.0f, 0.0f}}; // top-left
+            spriteVertices[baseIndex + 2] = {{centerX - halfWidth, centerY + halfHeight}, {colors[i][0], colors[i][1], colors[i][2], colors[i][3]}, {0.0f, 0.0f}};
 
             // Segundo triángulo (bottom-right, top-right, top-left)
-        spriteVertices[3] = {{ halfWidth, -halfHeight}, {1.0f, 1.0f}}; // bottom-right
+            spriteVertices[baseIndex + 3] = {{centerX + halfWidth, centerY - halfHeight}, {colors[i][0], colors[i][1], colors[i][2], colors[i][3]}, {1.0f, 1.0f}};
-        spriteVertices[4] = {{ halfWidth,  halfHeight}, {1.0f, 0.0f}}; // top-right
+            spriteVertices[baseIndex + 4] = {{centerX + halfWidth, centerY + halfHeight}, {colors[i][0], colors[i][1], colors[i][2], colors[i][3]}, {1.0f, 0.0f}};
-        spriteVertices[5] = {{-halfWidth,  halfHeight}, {0.0f, 0.0f}}; // top-left
+            spriteVertices[baseIndex + 5] = {{centerX - halfWidth, centerY + halfHeight}, {colors[i][0], colors[i][1], colors[i][2], colors[i][3]}, {0.0f, 0.0f}};
+        }
 
         // Copiar vértices al buffer
         void* spriteData = [spriteVertexBuffer contents];
         memcpy(spriteData, spriteVertices, sizeof(spriteVertices));
 
-        // Configurar vertex buffer y dibujar
+        // Configurar vertex buffer y dibujar todos los sprites en offscreen
-        [renderEncoder setVertexBuffer:spriteVertexBuffer offset:0 atIndex:0];
+        [offscreenEncoder setVertexBuffer:spriteVertexBuffer offset:0 atIndex:0];
-        [renderEncoder drawPrimitives:MTLPrimitiveTypeTriangle vertexStart:0 vertexCount:6];
+        [offscreenEncoder drawPrimitives:MTLPrimitiveTypeTriangle vertexStart:0 vertexCount:30];
 
-        [renderEncoder endEncoding];
+        [offscreenEncoder endEncoding];
+
+        // PASO 2: Aplicar CRT post-processing a la pantalla final
+        MTLRenderPassDescriptor* finalRenderPassDescriptor = [MTLRenderPassDescriptor renderPassDescriptor];
+        finalRenderPassDescriptor.colorAttachments[0].texture = drawable.texture;
+        finalRenderPassDescriptor.colorAttachments[0].loadAction = MTLLoadActionClear;
+        finalRenderPassDescriptor.colorAttachments[0].clearColor = MTLClearColorMake(0.0, 0.0, 0.0, 1.0);
+        finalRenderPassDescriptor.colorAttachments[0].storeAction = MTLStoreActionStore;
+
+        // Crear encoder para CRT post-processing
+        id<MTLRenderCommandEncoder> crtEncoder = [commandBuffer renderCommandEncoderWithDescriptor:finalRenderPassDescriptor];
+        if (!crtEncoder) {
+            continue;
+        }
+
+        // Aplicar CRT shader al resultado offscreen
+        [crtEncoder setRenderPipelineState:crtPipelineState];
+        [crtEncoder setFragmentTexture:offscreenTexture atIndex:0];
+        [crtEncoder setFragmentSamplerState:crtSampler atIndex:0];
+        [crtEncoder drawPrimitives:MTLPrimitiveTypeTriangle vertexStart:0 vertexCount:6];
+
+        [crtEncoder endEncoding];
 
         // Presentar drawable
         [commandBuffer presentDrawable:drawable];