primera implementacio de postfx

data/shaders/postfx.frag

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+#version 450
+
+// Vulkan GLSL fragment shader — PostFX effects
+// Used for SDL3 GPU API (SPIR-V path, Win/Linux).
+// Compile: glslc postfx.frag -o postfx.frag.spv
+//          xxd -i postfx.frag.spv > ../../source/core/rendering/sdl3gpu/postfx_frag_spv.h
+//
+// PostFXUniforms must match exactly the C++ struct in sdl3gpu_shader.hpp
+// (8 floats, 32 bytes, std140/scalar layout).
+
+layout(location = 0) in  vec2 v_uv;
+layout(location = 0) out vec4 out_color;
+
+layout(set = 2, binding = 0) uniform sampler2D scene;
+
+layout(set = 3, binding = 0) uniform PostFXUniforms {
+    float vignette_strength;
+    float chroma_strength;
+    float scanline_strength;
+    float screen_height;
+    float mask_strength;
+    float gamma_strength;
+    float curvature;
+    float bleeding;
+    float pixel_scale;   // physical pixels per logical pixel (vh / tex_height_)
+    float time;          // seconds since SDL init
+    float oversample;    // supersampling factor (1.0 = off, 3.0 = 3×SS)
+    float flicker;       // 0 = off, 1 = phosphor flicker ~50 Hz — 48 bytes total (3 × 16)
+} u;
+
+// YCbCr helpers for NTSC bleeding
+vec3 rgb_to_ycc(vec3 rgb) {
+    return vec3(
+         0.299*rgb.r + 0.587*rgb.g + 0.114*rgb.b,
+        -0.169*rgb.r - 0.331*rgb.g + 0.500*rgb.b + 0.5,
+         0.500*rgb.r - 0.419*rgb.g - 0.081*rgb.b + 0.5
+    );
+}
+vec3 ycc_to_rgb(vec3 ycc) {
+    float y  = ycc.x;
+    float cb = ycc.y - 0.5;
+    float cr = ycc.z - 0.5;
+    return clamp(vec3(
+        y + 1.402*cr,
+        y - 0.344*cb - 0.714*cr,
+        y + 1.772*cb
+    ), 0.0, 1.0);
+}
+
+void main() {
+    vec2 uv = v_uv;
+
+    // Curvatura barrel CRT
+    if (u.curvature > 0.0) {
+        vec2 c = uv - 0.5;
+        float rsq = dot(c, c);
+        vec2 dist = vec2(0.05, 0.1) * u.curvature;
+        vec2 barrelScale = vec2(1.0) - 0.23 * dist;
+        c += c * (dist * rsq);
+        c *= barrelScale;
+        if (abs(c.x) >= 0.5 || abs(c.y) >= 0.5) {
+            out_color = vec4(0.0, 0.0, 0.0, 1.0);
+            return;
+        }
+        uv = c + 0.5;
+    }
+
+    // Muestra base
+    vec3 base = texture(scene, uv).rgb;
+
+    // Sangrado NTSC — difuminado horizontal de crominancia.
+    // step = 1 pixel lógico de juego en UV (corrige SS: textureSize.x = game_w * oversample).
+    vec3 colour;
+    if (u.bleeding > 0.0) {
+        float tw   = float(textureSize(scene, 0).x);
+        float step = u.oversample / tw;  // 1 pixel lógico en UV
+        vec3 ycc    = rgb_to_ycc(base);
+        vec3 ycc_l2 = rgb_to_ycc(texture(scene, uv - vec2(2.0*step, 0.0)).rgb);
+        vec3 ycc_l1 = rgb_to_ycc(texture(scene, uv - vec2(1.0*step, 0.0)).rgb);
+        vec3 ycc_r1 = rgb_to_ycc(texture(scene, uv + vec2(1.0*step, 0.0)).rgb);
+        vec3 ycc_r2 = rgb_to_ycc(texture(scene, uv + vec2(2.0*step, 0.0)).rgb);
+        ycc.yz = (ycc_l2.yz + ycc_l1.yz*2.0 + ycc.yz*2.0 + ycc_r1.yz*2.0 + ycc_r2.yz) / 8.0;
+        colour = mix(base, ycc_to_rgb(ycc), u.bleeding);
+    } else {
+        colour = base;
+    }
+
+    // Aberración cromática (drift animado con time para efecto NTSC real)
+    float ca = u.chroma_strength * 0.005 * (1.0 + 0.15 * sin(u.time * 7.3));
+    colour.r = texture(scene, uv + vec2(ca, 0.0)).r;
+    colour.b = texture(scene, uv - vec2(ca, 0.0)).b;
+
+    // Corrección gamma (linealizar antes de scanlines, codificar después)
+    if (u.gamma_strength > 0.0) {
+        vec3 lin = pow(colour, vec3(2.4));
+        colour = mix(colour, lin, u.gamma_strength);
+    }
+
+    // Scanlines — 1 pixel físico oscuro por fila lógica.
+    // Usa uv.y (independiente del offset de letterbox) con pixel_scale para
+    // calcular la posición dentro de la fila en coordenadas físicas.
+    // 3x: 1 dark + 2 bright. 4x: 1 dark + 3 bright.
+    // bright=3.5×, dark floor=0.42 (mantiene aspecto CRT original).
+    if (u.scanline_strength > 0.0) {
+        float ps          = max(1.0, round(u.pixel_scale));
+        float frac_in_row = fract(uv.y * u.screen_height);
+        float row_pos     = floor(frac_in_row * ps);
+        float is_dark     = step(ps - 1.0, row_pos);
+        float scan        = mix(3.5, 0.42, is_dark);
+        colour           *= mix(1.0, scan, u.scanline_strength);
+    }
+
+    if (u.gamma_strength > 0.0) {
+        vec3 enc = pow(colour, vec3(1.0 / 2.2));
+        colour = mix(colour, enc, u.gamma_strength);
+    }
+
+    // Viñeta
+    vec2 d = uv - 0.5;
+    float vignette = 1.0 - dot(d, d) * u.vignette_strength;
+    colour *= clamp(vignette, 0.0, 1.0);
+
+    // Máscara de fósforo RGB — después de scanlines (orden original):
+    // filas brillantes saturadas → máscara invisible, filas oscuras → RGB visible.
+    if (u.mask_strength > 0.0) {
+        float whichMask = fract(gl_FragCoord.x * 0.3333333);
+        vec3 mask = vec3(0.80);
+        if (whichMask < 0.3333333)
+            mask.x = 1.0;
+        else if (whichMask < 0.6666666)
+            mask.y = 1.0;
+        else
+            mask.z = 1.0;
+        colour = mix(colour, colour * mask, u.mask_strength);
+    }
+
+    // Parpadeo de fósforo CRT (~50 Hz)
+    if (u.flicker > 0.0) {
+        float flicker_wave = sin(u.time * 100.0) * 0.5 + 0.5;
+        colour *= 1.0 - u.flicker * 0.04 * flicker_wave;
+    }
+
+    out_color = vec4(colour, 1.0);
+}

data/shaders/postfx.vert

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+#version 450
+
+// Vulkan GLSL vertex shader — postfx full-screen triangle
+// Used for SDL3 GPU API (SPIR-V path, Win/Linux).
+// Compile: glslc postfx.vert -o postfx.vert.spv
+//          xxd -i postfx.vert.spv > ../../source/core/rendering/sdl3gpu/postfx_vert_spv.h
+
+layout(location = 0) out vec2 v_uv;
+
+void main() {
+    // Full-screen triangle (no vertex buffer needed)
+    const vec2 positions[3] = vec2[3](
+        vec2(-1.0, -1.0),
+        vec2( 3.0, -1.0),
+        vec2(-1.0,  3.0)
+    );
+    const vec2 uvs[3] = vec2[3](
+        vec2(0.0, 1.0),
+        vec2(2.0, 1.0),
+        vec2(0.0,-1.0)
+    );
+    gl_Position = vec4(positions[gl_VertexIndex], 0.0, 1.0);
+    v_uv        = uvs[gl_VertexIndex];
+}