lower memory use for particle dataHEADmaster

1 files changed, 65 insertions, 54 deletions

diff --git a/main.c b/main.c
index e4bd106..5c8b5d9 100644
--- a/main.c
+++ b/main.c
@@ -38,10 +38,10 @@
 #define USE_GL_DEBUG false
 
 // number of particles
-#define NUM_PARTICLES 1024
+#define NUM_PARTICLES 2048
 
 // size of compute shader workgroups
-#define WORKGROUP_SIZE 128
+#define WORKGROUP_SIZE 1024
 
 typedef struct {
   const GLuint type;
@@ -72,17 +72,25 @@ verts[] = {
 };
 
 typedef struct {
-  float positions[4 * NUM_PARTICLES],
-        velocities[4 * NUM_PARTICLES],
-        colors[4 * NUM_PARTICLES];
+  float x, y;
+} vec2_t;
+
+typedef struct {
+  vec2_t positions[NUM_PARTICLES],
+         velocities[NUM_PARTICLES];
+  uint32_t colors[NUM_PARTICLES];
+  struct {
+    float r, g, b, a;
+  } palette[256];
 } particles_t;
 
 // shared particle shader storage buffer definition
 #define PARTICLE_BUFFER \
   "layout (std430, binding = 1) buffer particles {\n"   \
-  "  mediump vec4 positions[" S(NUM_PARTICLES) "];\n"   \
-  "  mediump vec4 velocities[" S(NUM_PARTICLES) "];\n"  \
-  "  mediump vec4 colors[" S(NUM_PARTICLES) "];\n"      \
+  "  mediump vec2 positions[" S(NUM_PARTICLES) "];\n"   \
+  "  mediump vec2 velocities[" S(NUM_PARTICLES) "];\n"  \
+  "  mediump uint colors[" S(NUM_PARTICLES) "];\n"      \
+  "  mediump vec4 palette[256];\n"                      \
   "};\n"
 
 // real compute shader
@@ -101,7 +109,7 @@ cs_src[] =
   "\n"
   "void main() {\n"
   "  mediump uint i = gl_GlobalInvocationID.x;\n"
-  "  positions[i].xy += delta * velocities[i].xy;\n"
+  "  positions[i] += delta * velocities[i];\n"
   "\n"
   "  if (positions[i].x > 1.1) {\n"
   "    positions[i].x -= 2.2;\n"
@@ -127,7 +135,7 @@ vs_src[] =
   "out mediump flat int instance_id;\n"
   "\n"
   "void main() {\n"
-  "  gl_Position = positions[gl_InstanceID] + 0.025 * vec4(pos, 1);\n"
+  "  gl_Position = vec4(positions[gl_InstanceID], 0, 1) + 0.025 * vec4(pos, 1);\n"
   "  instance_id = gl_InstanceID;\n"
   "}\n";
 
@@ -145,7 +153,7 @@ fs_src[] =
   "\n"
   "void main() {\n"
   "  mediump float alpha = 0.5f + 0.5f * (0.5f + 0.5 * sin(time * 3.141));\n"
-  "  color = vec4(colors[instance_id].rgb, 1) * alpha;\n"
+  "  color = palette[colors[instance_id]] * alpha;\n"
   "}\n";
 
 static const shader_t
@@ -267,12 +275,32 @@ color_map(uint8_t bits) {
   }
 }
 
+static void
+init_palette(
+  particles_t * const data
+) {
+  // generate palette seed data
+  uint8_t seeds[256];
+  if (!RAND_bytes(seeds, 256)) {
+    LOG_C("RAND_bytes() failed");
+    exit(EXIT_FAILURE);
+  }
+
+  #pragma omp parallel for
+  for (int i = 0; i < 256; i++) {
+    // get seed
+    const uint8_t cs = seeds[i];
+
+    // set color
+    data->palette[i].r = color_map(cs & 0x3);
+    data->palette[i].g = color_map((cs >> 2) & 0x3);
+    data->palette[i].b = color_map((cs >> 4) & 0x3);
+    data->palette[i].a = 1.0;
+  }
+}
+
 static GLuint
 init_particles(void) {
-  // create shader storage buffer
-  GLuint ssbo;
-  glGenBuffers(1, &ssbo);
-
   // generate seed data
   uint8_t seeds[5 * NUM_PARTICLES];
   if (!RAND_bytes(seeds, 5 * NUM_PARTICLES)) {
@@ -282,44 +310,27 @@ init_particles(void) {
 
   // populate particle data
   particles_t data;
-
   #pragma omp parallel for
   for (int i = 0; i < NUM_PARTICLES; i++) {
-    // calculate position
-    const float px = 2.0 * seeds[5 * i + 0] / 0xFF - 1.0,
-                py = 2.0 * seeds[5 * i + 1] / 0xFF - 1.0;
-
-    // LOG_D("%f,%f", px, py);
-
     // set position
-    data.positions[4 * i + 0] = px;
-    data.positions[4 * i + 1] = py;
-    data.positions[4 * i + 2] = 0.0;
-    data.positions[4 * i + 3] = 1.0;
-
-    // calculate velocity
-    const float vx = 2.0 * seeds[5 * i + 2] / 0xFF - 1.0,
-                vy = 2.0 * seeds[5 * i + 3] / 0xFF - 1.0;
+    data.positions[i].x = 2.0 * seeds[5 * i + 0] / 0xFF - 1.0;
+    data.positions[i].y = 2.0 * seeds[5 * i + 1] / 0xFF - 1.0;
 
     // set velocity
-    data.velocities[4 * i + 0] = vx;
-    data.velocities[4 * i + 1] = vy;
-    data.velocities[4 * i + 2] = 0;
-    data.velocities[4 * i + 3] = 0;
-
-    // calculate color
-    const uint8_t cs = seeds[5 * i + 4];
-    const float r = color_map(cs & 0x3),
-                g = color_map((cs >> 2) & 0x3),
-                b = color_map((cs >> 4) & 0x3);
+    data.velocities[i].x = 2.0 * seeds[5 * i + 2] / 0xFF - 1.0;
+    data.velocities[i].y = 2.0 * seeds[5 * i + 3] / 0xFF - 1.0;
 
     // set color
-    data.colors[4 * i + 0] = r;
-    data.colors[4 * i + 1] = g;
-    data.colors[4 * i + 2] = b;
-    data.colors[4 * i + 3] = 1.0;
+    data.colors[i] = seeds[5 * i + 4] & 0x3f;
   }
 
+  // generate palette
+  init_palette(&data);
+
+  // create shader storage buffer
+  GLuint ssbo;
+  glGenBuffers(1, &ssbo);
+
   // populate buffer
   glBindBuffer(GL_SHADER_STORAGE_BUFFER, ssbo);
   glBufferData(GL_SHADER_STORAGE_BUFFER, sizeof(particles_t), &data, GL_DYNAMIC_DRAW);
@@ -391,19 +402,19 @@ update_particles(
     #pragma omp parallel for
     for (int i = 0; i < NUM_PARTICLES; i++) {
       // update x coordinate
-      data->positions[4 * i + 0] += delta * data->velocities[4 * i + 0];
-      if (data->positions[4 * i + 0] < -1.1) {
-        data->positions[4 * i + 0] += 2.2;
-      } else if (data->positions[4 * i + 0] > 1.1) {
-        data->positions[4 * i + 0] -= 2.2;
+      data->positions[i].x += delta * data->velocities[i].x;
+      if (data->positions[i].x < -1.1) {
+        data->positions[i].x += 2.2;
+      } else if (data->positions[i].x > 1.1) {
+        data->positions[i].x -= 2.2;
       }
 
       // update y coordinate
-      data->positions[4 * i + 1] += delta * data->velocities[4 * i + 1];
-      if (data->positions[4 * i + 1] < -1.1) {
-        data->positions[4 * i + 1] += 2.2;
-      } else if (data->positions[4 * i + 1] > 1.1) {
-        data->positions[4 * i + 1] -= 2.2;
+      data->positions[i].y += delta * data->velocities[i].y;
+      if (data->positions[i].y < -1.1) {
+        data->positions[i].y += 2.2;
+      } else if (data->positions[i].y > 1.1) {
+        data->positions[i].y -= 2.2;
       }
     }