add init_particles(), use SSBO

2 files changed, 65 insertions, 22 deletions

diff --git a/Makefile b/Makefile
index f0f7b3a..7ef6f8d 100644
--- a/Makefile
+++ b/Makefile
@@ -1,6 +1,6 @@
 CFLAGS=-std=c11 -fopenmp -W -Wall -pedantic -O2
 APP=compute-test
-LIBS=-fopenmp -lSDL2 -lGLEW -lGL
+LIBS=-fopenmp -lSDL2 -lGLEW -lGL -lcrypto
 OBJS=main.o
 
 .PHONY=all clean test
diff --git a/main.c b/main.c
index e112bfa..cc9ed66 100644
--- a/main.c
+++ b/main.c
@@ -1,6 +1,7 @@
 #include <stdbool.h>
 #include <stdlib.h>
 
+#include <openssl/rand.h>
 #include <GL/glew.h>
 #include <SDL2/SDL.h>
 
@@ -37,36 +38,35 @@ typedef struct {
 
 static const float
 verts[] = {
-  -0.5,  0.5, 0,
-   0.5,  0.5, 0,
-   0.0, -0.5, 0,
+  -1,  1, 0,
+   1,  1, 0,
+   0.0, -1, 0,
 };
 
 static const char
 vs_src[] =
   "#version 320 es\n"
   "\n"
-  "layout (std140, binding = 0) buffer particles {\n"
-  "  mediump vec4 positions[" S(NUM_PARTICLES) "];\n"
-  "  mediump vec4 velocities[" S(NUM_PARTICLES) "];\n"
-  "  mediump vec4 colors[" S(NUM_PARTICLES) "];\n"
+  "layout (std430, binding = 1) buffer particles {\n"
+  "  highp vec4 positions[" S(NUM_PARTICLES) "];\n"
+  "  highp vec4 velocities[" S(NUM_PARTICLES) "];\n"
+  "  highp vec4 colors[" S(NUM_PARTICLES) "];\n"
   "};\n"
   "\n"
   "layout (location = 0) in mediump vec3 pos;\n"
   "\n"
   "void main() {\n"
-  "  mediump float ofs = 0.002 * float(gl_InstanceID - 500);\n"
-  "  gl_Position = vec4(pos.x - ofs, pos.y, pos.z, 1);\n"
+  "  gl_Position = positions[gl_InstanceID] + 0.025 * vec4(pos, 1);\n"
   "}\n";
 
 static const char
 fs_src[] =
   "#version 320 es\n"
   "\n"
-  "layout (std140, binding = 0) buffer particles {\n"
-  "  mediump vec4 positions[" S(NUM_PARTICLES) "];\n"
-  "  mediump vec4 velocities[" S(NUM_PARTICLES) "];\n"
-  "  mediump vec4 colors[" S(NUM_PARTICLES) "];\n"
+  "layout (std430, binding = 1) buffer particles {\n"
+  "  highp vec4 positions[" S(NUM_PARTICLES) "];\n"
+  "  highp vec4 velocities[" S(NUM_PARTICLES) "];\n"
+  "  highp vec4 colors[" S(NUM_PARTICLES) "];\n"
   "};\n"
   "\n"
   "out mediump vec4 color;\n"
@@ -340,6 +340,56 @@ static Uint32 timer_cb(
   return interval;
 }
 
+static GLuint
+init_particles(void) {
+  // create shader storage buffer
+  GLuint ssbo;
+  glGenBuffers(1, &ssbo);
+
+  // generate seed data
+  uint8_t seeds[4 * NUM_PARTICLES];
+  if (!RAND_bytes(seeds, 4 * NUM_PARTICLES)) {
+    SDL_Log("RAND_bytes() failed");
+    exit(EXIT_FAILURE);
+  }
+
+  // populate data
+  float data[3 * 4 * NUM_PARTICLES];
+  #pragma omp parallel for
+  for (int i = 0; i < NUM_PARTICLES; i++) {
+    float x = 2.0 * seeds[4 * i + 0] / 0xFF - 1.0,
+          y = 2.0 * seeds[4 * i + 1] / 0xFF - 1.0;
+
+    // SDL_Log("%f,%f", x, y);
+
+    // populate position
+    data[4 * i + 0] = x;
+    data[4 * i + 1] = y;
+    data[4 * i + 2] = 0.0;
+    data[4 * i + 3] = 1.0;
+
+    // populate random velocity
+    data[4 * (NUM_PARTICLES + i) + 0] = 2.0 * seeds[4 * i + 2] / 0xFF - 1.0;
+    data[4 * (NUM_PARTICLES + i) + 1] = 2.0 * seeds[4 * i + 3] / 0xFF - 1.0;
+
+    // populate colors
+    data[4 * (2 * NUM_PARTICLES + i) + 0] = ((i % 3) == 0) ? 1.0 : 0.0;
+    data[4 * (2 * NUM_PARTICLES + i) + 1] = ((i % 3) == 1) ? 1.0 : 0.0;
+    data[4 * (2 * NUM_PARTICLES + i) + 2] = ((i % 3) == 2) ? 1.0 : 0.0;
+    data[4 * (2 * NUM_PARTICLES + i) + 3] = 1.0;
+  }
+
+  // populate buffer
+  glBindBuffer(GL_SHADER_STORAGE_BUFFER, ssbo);
+  glBufferData(GL_SHADER_STORAGE_BUFFER, sizeof(data), data, GL_STATIC_DRAW);
+  glBindBuffer(GL_SHADER_STORAGE_BUFFER, 0);
+
+  glBindBufferBase(GL_SHADER_STORAGE_BUFFER, 1, ssbo);
+
+  // return buffer
+  return ssbo;
+}
+
 int main(int argc, char *argv[]) {
   UNUSED(argc);
   UNUSED(argv);
@@ -357,14 +407,7 @@ int main(int argc, char *argv[]) {
   glBindVertexArray(vao);
 
   // generate shader storage buffer
-  GLuint ssbo;
-  glGenBuffers(1, &ssbo);
-  glBindBuffer(GL_SHADER_STORAGE_BUFFER, ssbo);
-  glBufferData(GL_SHADER_STORAGE_BUFFER, NUM_PARTICLES * 3 * 4 * sizeof(GLfloat), NULL, GL_STATIC_DRAW);
-  glBindBuffer(GL_SHADER_STORAGE_BUFFER, 0);
-
-  // bind uniform buffer to slot 0
-  // glBindBufferBase(GL_UNIFORM_BUFFER, 2, ubo);
+  GLuint ssbo = init_particles();
 
   // generate vertex buffer
   GLuint vbo;