shark: Render UI with compute

title/shark-shaders/build.rs

@@ -26,7 +26,7 @@ struct Shader {
     name: &'static str,
 }
 
-const SHADERS: [Shader; 5] = [
+const SHADERS: [Shader; 3] = [
     Shader {
         stage: ShaderStage::Vertex,
         name: "basic",
@@ -39,14 +39,6 @@ const SHADERS: [Shader; 5] = [
         stage: ShaderStage::Compute,
         name: "display_transform",
     },
-    Shader {
-        stage: ShaderStage::Vertex,
-        name: "ui",
-    },
-    Shader {
-        stage: ShaderStage::Fragment,
-        name: "ui",
-    },
 ];
 
 fn main() {

title/shark-shaders/shaders/display_transform.comp.glsl

@@ -1,12 +1,50 @@
 #version 460
 
-layout (local_size_x = 8, local_size_y = 8, local_size_z = 1) in;
+#extension GL_EXT_scalar_block_layout : require
+#extension GL_EXT_control_flow_attributes : require
+
+struct CachedGlyph {
+    uint x0;
+    uint x1;
+    uint y0;
+    uint y1;
+
+    float offset_x0;
+    float offset_x1;
+    float offset_y0;
+    float offset_y1;
+};
+
+struct GlyphInstance {
+    float x;
+    float y;
+    uint index;
+    uint color;
+};
+
+layout(std430, set = 0, binding = 0) uniform uniformBuffer {
+    uint screen_width;
+    uint screen_height;
+    uint atlas_width;
+    uint atlas_height;
+    uint num_primitives;
+};
+
+layout (set = 0, binding = 1, rgba16f) uniform readonly image2D render_target;
+layout (set = 0, binding = 2, rgba16f) uniform writeonly image2D swapchain_image;
 
-layout (set = 0, binding = 0) uniform sampler linear_sampler;
+layout (set = 0, binding = 3) uniform sampler bilinear_sampler;
 
-layout (set = 0, binding = 1) uniform texture3D tony_mc_mapface_lut;
-layout (set = 0, binding = 2, rgba16f) uniform readonly image2D render_target;
-layout (set = 0, binding = 3, rgba16f) uniform writeonly image2D swapchain_image;
+layout (set = 0, binding = 4) uniform texture2D glyph_atlas;
+layout (set = 0, binding = 5) uniform texture3D tony_mc_mapface_lut;
+
+layout(std430, set = 0, binding = 6) readonly buffer glyphBuffer {
+    CachedGlyph cached_glyphs[];
+};
+
+layout(std430, set = 0, binding = 7) readonly buffer glyphInstanceBuffer {
+    GlyphInstance glyph_instances[];
+};
 
 float srgb_oetf(float a) {
     return (.0031308f >= a) ? 12.92f * a : 1.055f * pow(a, .4166666666666667f) - .055f;
@@ -20,11 +58,37 @@ vec3 tony_mc_mapface(vec3 stimulus) {
     const vec3 encoded = stimulus / (stimulus + 1.0);
     const float LUT_DIMS = 48.0;
     const vec3 uv = (encoded * ((LUT_DIMS - 1.0) / LUT_DIMS) + 0.5 / LUT_DIMS);
-    return textureLod(sampler3D(tony_mc_mapface_lut, linear_sampler), uv, 0.0).rgb;
+    return textureLod(sampler3D(tony_mc_mapface_lut, bilinear_sampler), uv, 0.0).rgb;
 }
 
+layout (local_size_x = 8, local_size_y = 8, local_size_z = 1) in;
+
 void main() {
+    vec4 accum = vec4(0.0);
+
+    for (int i = 0; i < num_primitives; i++) {
+        const GlyphInstance gi = glyph_instances[i];
+        const CachedGlyph cg = cached_glyphs[gi.index];
+        const vec4 color = unpackUnorm4x8(gi.color).bgra;
+        const vec2 glyph_top_left = vec2(gi.x + cg.offset_x0, gi.y + cg.offset_y0);
+        const vec2 glyph_bottom_right = vec2(gi.x + cg.offset_x1, gi.y + cg.offset_y1);
+        const vec2 glyph_size = vec2(cg.offset_x1 - cg.offset_x0, cg.offset_y1 - cg.offset_y0);
+        const vec2 sample_center = gl_GlobalInvocationID.xy; // half pixel offset goes here?
+        if (sample_center.x >= glyph_top_left.x &&
+            sample_center.x <= glyph_bottom_right.x &&
+            sample_center.y >= glyph_top_left.y &&
+            sample_center.y <= glyph_bottom_right.y) {
+            const vec2 uv = mix(vec2(cg.x0, cg.y0), vec2(cg.x1, cg.y1), (sample_center - glyph_top_left) / glyph_size) / vec2(atlas_width, atlas_height);
+            const float coverage = textureLod(sampler2D(glyph_atlas, bilinear_sampler), uv, 0.0).r;
+            accum = coverage * color;
+            accum.a = coverage;
+            break;
+        }
+    }
+
     vec3 stimulus = imageLoad(render_target, ivec2(gl_GlobalInvocationID.xy)).rgb;
-    vec3 srgb = srgb_oetf(tony_mc_mapface(stimulus));
-    imageStore(swapchain_image, ivec2(gl_GlobalInvocationID.xy), vec4(srgb, 1.0));
+    vec3 transformed = tony_mc_mapface(stimulus);
+    vec3 srgb = srgb_oetf(transformed);
+    vec3 composited = accum.rgb + (srgb * (1.0 - accum.a));
+    imageStore(swapchain_image, ivec2(gl_GlobalInvocationID.xy), vec4(composited, 1.0));
 }