Make PBO speedier

diff --git a/clouds.cpp b/clouds.cpp
index ff6e59d8faca801d28a5638897a28e115ffb0b37..5787181c79fbac832a0984d362a654eaaa6ae619 100644 (file)
--- a/clouds.cpp
+++ b/clouds.cpp
@@ -167,7 +167,7 @@ mat4 faceView(mat4 m) {
 const int shadeWidth = 256, shadeHeight = 256;
 
 #ifdef PBO
-const int numPbos = 64;
+const int numPbos = 512;
 GLuint pboBufs[numPbos];
 GLuint pboOffsets[numPbos]; // offsets into GL_PIXEL_PACK_BUFFER that
                             // mapPixelRead should read from
@@ -176,8 +176,10 @@ GLbyte sink[shadeWidth * shadeHeight * 4];
 void inline mapPixelRead(int pboBuf, int metaball) {
   glBindBuffer(GL_PIXEL_PACK_BUFFER, pboBufs[pboBuf]);
   GLubyte *src =
-      (GLubyte *)glMapBufferRange(GL_PIXEL_PACK_BUFFER, pboOffsets[pboBuf],
+      (GLubyte *)glMapBufferRange(GL_PIXEL_PACK_BUFFER, 0,
                                   4 * sizeof(GLubyte), GL_MAP_READ_BIT);
+      /* (GLubyte *)glMapBufferRange(GL_PIXEL_PACK_BUFFER, pboOffsets[pboBuf], */
+      /*                             4 * sizeof(GLubyte), GL_MAP_READ_BIT); */
   vec4 pixel = vec4(src[0], src[1], src[2], src[3]) / vec4(255.f);
   glUnmapBuffer(GL_PIXEL_PACK_BUFFER);
 
@@ -272,9 +274,10 @@ void shadeClouds() {
     /* glReadPixels(screenPos.x, screenPos.y, 1, 1, GL_RGBA, GL_UNSIGNED_BYTE,
      */
     /*              NULL); */
-    glReadPixels(0, 0, shadeWidth, shadeHeight, GL_RGBA, GL_UNSIGNED_BYTE,
-                 NULL);
-    pboOffsets[pboIdx] = screenPos.x * 4 + screenPos.y * shadeWidth * 4;
+    /* glReadPixels(0, 0, shadeWidth, shadeHeight, GL_RGBA, GL_UNSIGNED_BYTE, */
+    /*              NULL); */
+    glReadPixels(screenPos.x, screenPos.y, 64, 64, GL_RGBA, GL_UNSIGNED_BYTE, NULL);
+    /* pboOffsets[pboIdx] = screenPos.x * 4 + screenPos.y * shadeWidth * 4; */
 
     int nextPbo = (pboIdx + 1) % numPbos;
     if (i >= numPbos - 1) {
@@ -549,7 +552,7 @@ int main(int argc, char **argv) {
   glGenBuffers(numPbos, pboBufs);
   for (int i = 0; i < numPbos; i++) {
     glBindBuffer(GL_PIXEL_PACK_BUFFER, pboBufs[i]);
-    glBufferData(GL_PIXEL_PACK_BUFFER, shadeWidth * shadeHeight * 4, NULL,
+    glBufferData(GL_PIXEL_PACK_BUFFER, 64 * 64 * 4, NULL,
                  GL_DYNAMIC_READ);
   }
   glBindBuffer(GL_PIXEL_PACK_BUFFER, 0);