add multiple samples per pixel

launch

@@ -1,12 +1,13 @@
 #!/usr/bin/env bash
 
 executable="$1"
+options="$2"
 prime="prime-run"
 
 if command -v $prime &> /dev/null
 then
-    echo "launching $executable with nvidia prime offloading"
+    echo "launching $executable $options with nvidia prime offloading"
-    $prime $executable
+    $prime $executable $options
 else
-    $executable
+    $executable $options
 fi

makefile

@@ -46,7 +46,11 @@ clean:
 	-rm -r $(BIN_DIR)
 	-rm */*.o
 
+# TODO: extract run-* out to like, python scripts? arguments can be implemented with argparse to
+# manage simple interface with C binary
 run: $(TARGET)
-	$(LAUNCH) $(TARGET)
+	$(LAUNCH) $(TARGET) 1.0
+run-converge: $(TARGET) 
+	$(LAUNCH) $(TARGET) 0.0
 
 .PHONY: run clean

shader/include/constants.glsl

@@ -1,7 +1,7 @@
-const float INF = 50.0;
+const float INF = 30.0;
 const float PI = 3.14159;
 const float E = 2.71828;
-const int BOUNCES = 4;
+const int BOUNCES = 5;
 
 // materials
 const int MAT_SKY = -1;

shader/include/depth.glsl

@@ -0,0 +1,16 @@
+float getLinearDepth(float distance)
+{
+    return distance/INF;
+}
+
+float getLogarithmicDepth(float distance)
+{
+    // n roughly correlates to steepness of log curve
+    // TODO: what does this mean in mathematical terms??
+    float n = 4;
+    float f = INF;
+    float z = distance;
+    
+    // logarithmic depth
+    return max(0,log(z*pow(E,n)/f)/n);
+}

shader/include/intersect.glsl

@@ -33,7 +33,7 @@ void intersectPlane(Ray ray, inout RayHit bestHit, vec3 p, vec3 normal)
             bestHit.distance = t;
             bestHit.position = ray.origin + t*ray.direction;
             bestHit.normal = normal;
-            bestHit.albedo = vec3(1.0,1.0,1.0);
+            bestHit.albedo = vec3(1.0,.4,.4);
             bestHit.material = MAT_LAMBERT;
         }
     }

shader/include/ray.glsl

@@ -3,6 +3,7 @@ struct Ray
     vec3 origin;
     vec3 direction;
     vec3 energy;
+    float distance;
 };
 Ray createRay(vec3 origin, vec3 direction)
 {
@@ -11,6 +12,7 @@ Ray createRay(vec3 origin, vec3 direction)
     ray.origin = origin;
     ray.direction = direction;
     ray.energy = vec3(1.0,1.0,1.0);
+    ray.distance = 0;
 
     return ray;
 }

shader/include/scene.glsl

@@ -1,19 +1,17 @@
-RayHit trace(Ray ray)
+RayHit trace(inout Ray ray)
 {
     RayHit hit = createRayHit();
 
-    Sphere s;
+    // floor
-    s.cr = vec4(0.0,0.0,0.0,5.0);
-    s.albedo = vec3(1.0,0.0,0.0);
-    s.material = MAT_CHROME;
-    intersectSphere(ray, hit, s);
-
     intersectPlane(ray, hit, vec3(0.0,-1.5,0.0),vec3(0.0,1.0,0.0));
 
+    // spheres
     for (int i = 0; i < _activeSpheres; i++)
     {
         intersectSphere(ray, hit, _spheres[i]);
     }
 
+    ray.distance += hit.distance * float(hit.distance < INF);
+
     return hit;
 }

shader/root/rt.glsl

@@ -24,6 +24,7 @@ uniform vec3 _skyColor = vec3(0.68,0.85,0.9);
 // scene.glsl includes scene trace function
 #include scene.glsl     
 #include lighting.glsl
+#include depth.glsl
 
 vec3 shade(inout Ray ray, RayHit hit)
 {
@@ -77,14 +78,25 @@ void main()
     int bounces = (1-sky) * BOUNCES; 
     pixel.xyz = mix(pixel.xyz, _skyColor, sky);
 
-    // trace the rays path around the scene
+    // sample
-    for (int j = 0; j < bounces; j++)
+    int samples = 2;
+    for (int i = 0; i < samples; i++)
     {
-        RayHit hit = trace(ray);
+        float sampleDepth = 0;
 
-        pixel.xyz += ray.energy * shade(ray, hit);
+        // trace the ray's path around the scene
+        for (int j = 0; j < bounces; j++)
+        {
+            RayHit hit = trace(ray);
 
-        if (length(ray.energy) < 0.001) break;
+            depth = getLogarithmicDepth(ray.distance);
+
+            pixel.xyz += ray.energy * shade(ray, hit);
+
+            if (length(ray.energy) < 0.001) break;
+        }
+
+        depth += sampleDepth / float(samples);
     }
 
     pixel.xyz = mix(pixel.xyz, vec3(1.0), depth);

shader/root/rtpre.glsl

@@ -18,6 +18,7 @@ layout (rgba32f, binding = 3) writeonly uniform image2D g1_output;
 #include camera.glsl
 #include image.glsl
 #include scene.glsl
+#include depth.glsl
 
 void main()
 {
@@ -34,18 +35,7 @@ void main()
     Ray ray = createCameraRay(uv);
     RayHit hit = trace(ray);
 
-    // n roughly correlates to steepness of log curve
+    float depth = getLogarithmicDepth(hit.distance);
-    // TODO: what does this mean in mathematical terms??
-    float n = 4;
-    float f = INF;
-    float z = hit.distance;
-    
-    float depth;
-    // linear depth
-    //depth = z/f;
-
-    // logarithmic depth
-    depth = max(0,log(z*pow(E,n)/f)/n);
 
     // pack normal into texture
     pixel.xyz = hit.normal*0.5+0.5;

src/cam.c

@@ -2,10 +2,8 @@
 
 const float FOVY = 90.0;
 
-void updateCameraUniforms(GLuint shaderProgram, float aspect)
+void updateCameraUniforms(GLuint shaderProgram, float aspect, float t)
 {
-    float t = now();
-
     // wobble up dir
     vec3 cdir, cright, cup;
     vec3 up = {0.1*sin(t),1.0,0.05*cos(0.5*t)};

src/cam.h

@@ -6,4 +6,4 @@
 
 #include "clock.h"
 
-void updateCameraUniforms(GLuint shaderProgram, float aspect);
+void updateCameraUniforms(GLuint shaderProgram, float aspect, float t);

src/clock.c

@@ -1,6 +1,11 @@
 #include "clock.h"
 
-float now() 
+float now()
-{ 
+{
-    return (float)SDL_GetTicks() / 1000.0; 
+    return (float)SDL_GetTicks() / 1000.0;
+}
+
+float nowScaled(struct Epoch t)
+{ 
+    return t.scale * now();
 }

src/clock.h

@@ -2,5 +2,12 @@
 
 #include <SDL2/SDL.h>
 
-// seconds since program start
+struct Epoch
+{
+    float scale;
+};
+
+// real seconds since program start
 float now();
+// simulation seconds since program start
+float nowScaled(struct Epoch e);

src/gfx.c

@@ -174,16 +174,6 @@ void setVertexAttributes()
     // color
     glVertexAttribPointer(1, 3, GL_FLOAT, GL_FALSE, stride, (void*)(3*sizeof(float)));
     glEnableVertexAttribArray(1);
-
-
-
-
-
-
-
-
-
-
     // uv 
     glVertexAttribPointer(2, 2, GL_FLOAT, GL_FALSE, stride, (void*)(6*sizeof(float)));
     glEnableVertexAttribArray(2);

src/main.c

@@ -10,12 +10,13 @@
 const int WIDTH = 420;
 const int HEIGHT = 420;
 
-void updateUniforms(GLuint shaderProgram);
+void updateUniforms(GLuint shaderProgram, float t);
 
 SDL_Window *window;
 
 struct Shaders shaders;
 struct Textures textures;
+struct Epoch epoch;
 
 void initialise()
 {
@@ -32,8 +33,21 @@ void initialise()
     createTextures(WIDTH, HEIGHT, shaders, &textures);
 }
 
-int main()
+void parseArgs(int argc, char* argv[], struct Epoch* e)
 {
+    // check we have the right number of arguments
+    if (argc != 2)
+    {
+        fprintf(stderr, "usage: oglc TIMESPEED\n");
+    }
+
+    sscanf(argv[1], "%f", &(e->scale));
+}
+
+int main(int argc, char* argv[])
+{
+    parseArgs(argc, argv, &epoch);
+
     initialise();
 
     float start = now();
@@ -41,6 +55,7 @@ int main()
     for (frames = 0; !checkQuit(); frames++)
     {
         GLuint shader;
+        float t = nowScaled(epoch);
 
         // prepass
         // TODO: write output to different texture than main output
@@ -48,18 +63,17 @@ int main()
         glActiveTexture(GL_TEXTURE0);
         glBindTexture(GL_TEXTURE_2D, textures.g0);
         glUseProgram(shader);
-        updateUniforms(shader);
+        updateUniforms(shader, t);
         glDispatchCompute((GLuint)WIDTH, (GLuint)HEIGHT, 1);
 
         // make sure we're finished writing to the texture before trying to read it
         glMemoryBarrier(GL_ALL_BARRIER_BITS);
 
-        // dispatch compute shaders
         shader = shaders.lighting;
         glActiveTexture(GL_TEXTURE0);
         glBindTexture(GL_TEXTURE_2D, textures.target);
         glUseProgram(shader);
-        updateUniforms(shader);
+        updateUniforms(shader, t);
         //int loc = glGetUniformLocation(shader, "_g0");
         //glUniform1i(loc, textures.g0);
         glDispatchCompute((GLuint)WIDTH, (GLuint)HEIGHT, 1);
@@ -67,6 +81,18 @@ int main()
         // make sure we're finished writing to the texture before trying to read it
         glMemoryBarrier(GL_SHADER_IMAGE_ACCESS_BARRIER_BIT);
 
+        // TODO: frame blending
+        //
+        // before we get to our normal rendering pass we need to blend our samples
+        // across multiple frames. to do this, we should maintain an accumulation
+        // buffer where we can store pixel data while a new frame is being generated.
+        // this can be a collection of two buffers, where one is written to and the 
+        // other is read from. to render a new frame, the newly sampled raw frame can
+        // be combined with data from the previous frame. by repeatedly taking the
+        // average over a large number of frames a cleaner image can be generated.
+        // this is most effective for static images, and will produce motion blur on
+        // a moving image.
+
         // normal drawing pass
         shader = shaders.quad;
         glUseProgram(shader);
@@ -87,7 +113,7 @@ int main()
     return 0;
 }
 
-void updateUniforms(GLuint shaderProgram)
+void updateUniforms(GLuint shaderProgram, float t)
 {
     // update random values
     vec4 seed = 
@@ -100,19 +126,17 @@ void updateUniforms(GLuint shaderProgram)
     int loc = glGetUniformLocation(shaderProgram, "_seed");
     glUniform4fv(loc, 1, seed);
 
-    // update time
-    float t = now();
     float sin_t = sin(t);
     loc = glGetUniformLocation(shaderProgram, "_t");
     glUniform4f(loc, t, sin_t, (1.0 + sin_t)*0.5, 0.0f);
 
     // update camera
     float aspect = (float)WIDTH/(float)HEIGHT;
-    updateCameraUniforms(shaderProgram, aspect);
+    updateCameraUniforms(shaderProgram, aspect, t);
 
     // make and update spheres
-    const int sphereCount = 42;
+    const int sphereCount = 41;
     struct Sphere spheres[sphereCount];
-    makeSpheres(spheres, sphereCount);
+    makeSpheres(spheres, sphereCount, t);
     updateSphereUniforms(shaderProgram, spheres, sphereCount);
 }

src/sphere.c

@@ -1,9 +1,7 @@
 #include "sphere.h"
 
-void makeSpheres(struct Sphere *spheres, int count)
+void makeSpheres(struct Sphere *spheres, int count, float t)
 {
-    //float t = time();
-
     vec3 albedos[] = 
     {
         {0.0,0.0,1.0},
@@ -15,21 +13,33 @@ void makeSpheres(struct Sphere *spheres, int count)
         {1.0,1.0,1.0}
     };
 
-    // distance from center
-    float d = 6.0;
-    float radius = 0.5;
-    float x;
     vec3 sc = {0.0,0.0,1.0};
 
-    float t = now();
+    int sphereIdx = 0;
-    for (int i = 0; i < count; i++)
+
+    // a shiny sphere in the middle which bobs around
+    int middleSpheres = 1;
+    sc[0] = 2.5*sin(t*2.67);
+    sc[1] = 1.5+sin(t*1.09);
+    sc[2] = 2.5*cos(-t*2.13);
+    float radius = 1.7;
+    vec3 col = {0.0,0.0,0.0};
+    spheres[sphereIdx++] = makeSphere(sc,radius,col,1);
+
+    // rainbow spheres
+    int rainbowSpheres = count - middleSpheres;
+    // distance from center
+    float d = 6.0;
+    radius = 0.5;
+    float x;
+    for (int i = 0; i < rainbowSpheres; i++)
     {
-        x = 2.0*CGLM_PI * (float)i/(float)count;
+        x = 2.0*CGLM_PI * (float)i/(float)rainbowSpheres;
         sc[0] = sin(x)*d;
         sc[1] = sin(x*3.0-5.0*sin(t));
         sc[2] = cos(x)*d;
 
-        float ic = i/(float)count*CGLM_PI*2.0;
+        float ic = i/(float)rainbowSpheres*CGLM_PI*2.0;
         float r = sin(ic);
         float g = sin(ic+CGLM_PI/1.5);
         float b = sin(ic+2.0*CGLM_PI/1.5);
@@ -38,8 +48,8 @@ void makeSpheres(struct Sphere *spheres, int count)
         glm_vec3_scale(col, 0.5, col);
         glm_vec3_adds(col, 0.5, col);
 
-        int material = i % 2 == 0;
+        int material = i % 2;
-        spheres[i] = makeSphere(sc,radius,col,material);
+        spheres[sphereIdx++] = makeSphere(sc,radius,col,material);
     }
 }
 

src/sphere.h

@@ -16,7 +16,7 @@ struct Sphere
     int material;
 };
 
-void makeSpheres(struct Sphere *spheres, int count);
+void makeSpheres(struct Sphere *spheres, int count, float t);
 struct Sphere makeSphere(vec3 center, float radius, vec3 albedo, int material);
 //void updateSphereUniform(GLuint shaderProgram, struct Sphere sphere);
 void updateSphereUniforms(GLuint shaderProgram, struct Sphere *spheres, int count);