extract noise to file

shader/quad/shader.frag

@@ -53,6 +53,6 @@ void main()
     float kSigma = 7.0;
     float threshold = 0.3;
 
-    FragColor = denoise(ourTexture, TexCoord, sigma, kSigma, threshold);
-    //FragColor = texture(ourTexture, TexCoord);
+    //FragColor = denoise(ourTexture, TexCoord, sigma, kSigma, threshold);
+    FragColor = texture(ourTexture, TexCoord);
 }

shader/root/rt.glsl

@@ -108,6 +108,8 @@ void main()
 
     pixel.xyz = mix(pixel.xyz, vec3(1.0), depth);
 
+    pixel.xyz = texture(_noise, uv*.5-.5).xyz;
+
     // output to a specific pixel in the image
     imageStore(img_output, ivec2(gl_GlobalInvocationID.xy), pixel);
 }

src/gfx.c

@@ -1,5 +1,4 @@
 #include "gfx.h"
-#include "random.h"
 
 float vertices[] = {
     // position             color               uvs
@@ -196,7 +195,6 @@ int createTextures(int width, int height, struct Shaders shaders, struct Texture
     return 0;
 }
 
-// creates a noise texture in active texture 1
 GLuint createNoiseTexture(int width, int height)
 {
     // same init steps as with a regular texture
@@ -212,14 +210,10 @@ GLuint createNoiseTexture(int width, int height)
 
     int channels = 4; // rgba
     int length = width*height*channels;
-    printf("generating %d random floats\n", length);
-
     float* data = (float*)malloc(length*sizeof(float));
 
-    for (int i = 0; i < length; i++)
-    {
-        data[i] = randomFloat();
-    }
+    //writeWhiteNoiseToTexture(data, width, height);
+    writeBlueNoiseToTexture(data, width, height);
 
     glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA32F, width, height, 0, GL_RGBA, GL_FLOAT, data);
     glBindImageTexture(0, texture, 0, GL_FALSE, 0, GL_READ_ONLY, GL_RGBA32F);

src/gfx.h

@@ -7,7 +7,7 @@
 #include <SDL2/SDL_opengl.h>
 
 #include "io.h"
-#include "random.h"
+#include "noise.h"
 
 struct Shaders
 {

src/noise.c

@@ -0,0 +1,131 @@
+#include "noise.h"
+
+void writeWhiteNoiseToTexture(float* data, int width, int height)
+{
+    int channels = 4; // rgba
+    int length = width*height*channels;
+
+    printf("generating %d random floats\n", length);
+    for (int i = 0; i < length; i++)
+    {
+        data[i] = randomFloat();
+    }
+}
+
+void generateBlueNoisePoints(vec2* points, int m, int n)
+{
+    float start = now();
+    float elapsed;
+    int candidatesTested = 0;
+
+    struct Candidate
+    {
+        vec2 pos;
+        // distance to closest point already in pattern
+        float distance;
+    };
+
+    for (int i = 0; i < n; i++)
+    {
+        // generate a bunch of candidates
+        int count = m * i;
+        struct Candidate candidates[count];
+
+        for (int j = 0; j < count; j++)
+        {
+            struct Candidate* c = &candidates[j];
+
+            c->pos[0] = randomFloat();
+            c->pos[1] = randomFloat();
+            // the largest distance we should expect is sqrt(2),
+            // so pick a maximum larger than that
+            c->distance = 1.5; 
+
+            // get the distance of the closest point already in the pattern
+            for (int k = 0; k < i; k++)
+            {
+                float distance = glm_vec2_distance(c->pos, points[k]);
+                if (distance < c->distance)
+                {
+                    c->distance = distance;
+                }
+            }
+
+            candidatesTested += i;
+
+            float killAfter = 10.0;
+            elapsed = now() - start;
+            if (elapsed > killAfter)
+            {
+                printf("noise generation took too long (%fs), exiting\n", elapsed);
+                exit(1);
+            }
+        }
+
+        // of our candidates, now determine which of them has the furthest
+        // closest-distance
+        int furthest = -1;
+        float furthestDistance = 0.0;
+        for (int j = 0; j < count; j++)
+        {
+            if (candidates[j].distance > furthestDistance)
+            {
+                furthest = j;
+                furthestDistance = candidates[j].distance;
+            }
+        }
+
+        glm_vec2_copy(candidates[furthest].pos, points[i]);
+    }
+
+    elapsed = now() - start;
+    printf("generated %d blue noise (m=%d) points from %d candidates in %fs\n",
+        n,
+        m,
+        candidatesTested,
+        elapsed);
+}
+
+void writeBlueNoiseToTexture(float* data, int width, int height)
+{
+    printf("generating blue noise\n");
+    int channels = 4;
+
+    // blue noise gen parameters
+    int m = 10;     // roughly controls the evenness...?
+    int n = 100;    // number of points to generate
+
+    // for each channel
+    for (int channel = 0; channel < channels; channel++)
+    {
+        // generate a bunch of points
+        vec2 points[n];
+        generateBlueNoisePoints(points, m, n);
+
+        for (int i = 0; i < width*height; i++)
+        {
+            int pixelIdx = i;
+            int x = pixelIdx % width;
+            int y = pixelIdx / width;
+            float u = x / (float)width;
+            float v = y / (float)height;
+            vec2 pixel = {u,v};
+
+            //float value = 0.0f;
+            int componentIdx = i * channels + channel;
+            for (int j = 0; j < n; j++)
+            {
+                float d = glm_vec2_distance(points[j], pixel);
+                //value += 1.0f / (d*d);
+
+                float r = 0.01;
+                if (d < r)
+                {
+                    data[componentIdx] = 1.0;
+                }
+            }
+            //data[componentIdx] = value / (float)n;
+        }
+    }
+}
+

src/noise.h

@@ -0,0 +1,13 @@
+#pragma once
+
+#include "GL/glew.h"
+#include <cglm/vec2.h>
+
+#include "io.h"
+#include "random.h"
+#include "clock.h"
+
+void writeWhiteNoiseToTexture(float* data, int width, int height);
+
+void generateBlueNoisePoints(vec2* points, int m, int n);
+void writeBlueNoiseToTexture(float* data, int width, int height);