use shader storage instead of uniform buffer, remove hard-coded particle count

1 files changed, 24 insertions, 20 deletions

diff --git a/main.c b/main.c
index e6aded0..e112bfa 100644
--- a/main.c
+++ b/main.c
@@ -12,6 +12,10 @@
 // custom SDL_USEREVENT code for timer
 #define EVENT_CODE_TIMER 0
 
+#define NUM_PARTICLES 1000
+#define SS(v) #v
+#define S(v) SS(v)
+
 typedef struct {
   const GLuint type;
   const char *src;
@@ -42,10 +46,10 @@ static const char
 vs_src[] =
   "#version 320 es\n"
   "\n"
-  "layout (std140, binding = 0) uniform particles {\n"
-  "  mediump vec4 positions[1000];\n"
-  "  mediump vec4 velocities[1000];\n"
-  "  mediump vec4 colors[1000];\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"
   "};\n"
   "\n"
   "layout (location = 0) in mediump vec3 pos;\n"
@@ -59,10 +63,10 @@ static const char
 fs_src[] =
   "#version 320 es\n"
   "\n"
-  "layout (std140, binding = 0) uniform particles {\n"
-  "  mediump vec4 positions[1000];\n"
-  "  mediump vec4 velocities[1000];\n"
-  "  mediump vec4 colors[1000];\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"
   "};\n"
   "\n"
   "out mediump vec4 color;\n"
@@ -352,15 +356,15 @@ int main(int argc, char *argv[]) {
   glGenVertexArrays(1, &vao);
   glBindVertexArray(vao);
 
-  // generate uniform buffer
-  GLuint ubo;
-  glGenBuffers(1, &ubo);
-  glBindBuffer(GL_UNIFORM_BUFFER, ubo);
-  glBufferData(GL_UNIFORM_BUFFER, 1000 * 3 * 4 * sizeof(GLfloat), NULL, GL_STATIC_DRAW);
-  glBindBuffer(GL_UNIFORM_BUFFER, 0);
+  // 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);
+  // glBindBufferBase(GL_UNIFORM_BUFFER, 2, ubo);
 
   // generate vertex buffer
   GLuint vbo;
@@ -375,8 +379,8 @@ int main(int argc, char *argv[]) {
   glBindVertexArray(0);
 
   // link program, get uniforms
-  GLuint prog = link_program(2, RENDER_SHADERS);
-  GLint u_time = glGetUniformLocation(prog, "time");
+  GLuint render_prog = link_program(2, RENDER_SHADERS);
+  GLint u_time = glGetUniformLocation(render_prog, "time");
 
   // main loop
   while (!ctx.done) {
@@ -390,13 +394,13 @@ int main(int argc, char *argv[]) {
     glClearColor(0, 0, 0, 1);
     glClear(GL_COLOR_BUFFER_BIT);
 
-    // use program, set uniform
-    glUseProgram(prog);
+    // use render program, set uniform
+    glUseProgram(render_prog);
     glUniform1f(u_time, now / 1000.0);
 
     // draw
     glBindVertexArray(vao);
-    glDrawArraysInstanced(GL_TRIANGLES, 0, 3, 1000);
+    glDrawArraysInstanced(GL_TRIANGLES, 0, 3, NUM_PARTICLES);
     glBindVertexArray(0);
 
     // swap buffer