Shadow Map Sample

core/cross/gl/renderer_gl.cc

Index: core/cross/gl/renderer_gl.cc
===================================================================
--- core/cross/gl/renderer_gl.cc	(revision 20998)
+++ core/cross/gl/renderer_gl.cc	(working copy)
@@ -1567,6 +1567,11 @@
   MakeCurrentLazy();
   Bitmap::Ref bitmap = Bitmap::Ref(new Bitmap(service_locator()));
   bitmap->Allocate(Texture::ARGB8, width(), height(), 1, false);
+  
+  // Note: glReadPixels caputres the alpha component of the frame buffer as well
+  // as the color components, the graphics pipeline usually ignores the alpha
+  // channel when drawing to the screen, so unless the alpha is 1, the png image
+  // generated might exhibit suprise translucency.
   ::glReadPixels(0, 0, width(), height(), GL_BGRA, GL_UNSIGNED_BYTE,
                  bitmap->image_data());
   bool result = bitmap->SaveToPNGFile((file_name + ".png").c_str());