I'm trying to draw to a renderbuffer (512x512) that's larger than the screen size (i.e., 320x480).
After doing a glReadPixels, the image looks correct, except once the dimensions of the image exceed that of the screen size- in this example, past 320 horizontal and 480 vertical. What causes this anomaly? Is there something I'm missing? When the window size is >= the size of the renderbuffer, this code works absolutely fine.
Example image that was rendered to the buffer & glReadPixel'd: http://img593.imageshack.us/img593/3220/rendertobroke.png
unsigned int canvasFrameBuffer; bglGenFramebuffers(1, &canvasFrameBuffer); bglBindFramebuffer(BGL_RENDERBUFFER, canvasFrameBuffer); // Attach renderbuffer unsigned int canvasRenderBuffer; bglGenRenderbuffers(1, &canvasRenderBuffer); bglBindRenderbuffer(BGL_RENDERBUFFER, canvasRenderBuffer); bglRenderbufferStorage(BGL_RENDERBUFFER, BGL_RGBA4, width, height); bglFramebufferRenderbuffer(BGL_FRAMEBUFFER, BGL_COLOR_ATTACHMENT0, BGL_RENDERBUFFER, canvasRenderBuffer); bglViewport(0, 0, width, height); Matrix::matrix_t identity, colorMatrix; Matrix::LoadIdentity(&identity); Matrix::LoadIdentity(&colorMatrix); bglClearColor(1.0f, 1.0f, 1.0f, 1.0f); bglClear(BGL_COLOR_BUFFER_BIT); Vector::vector_t oldPos, oldScale; Vector::Copy(&oldPos, &pos); Vector::Mul(&pos, 0.0f); Vector::Copy(&oldScale, &scale); Vector::Load(&scale, 1, 1, 1); int oldHAlign = halignment; int oldVAlign = valignment; halignment = Font::HALIGN_LEFT; valignment = Font::VALIGN_BOTTOM; float oldXRatio = vid.xratio; float oldYRatio = vid.yratio; vid.xratio = 1; vid.yratio = 1; Drawing::Set2D(this->size.x, this->size.y); // glOrtho and setup projection/modelview matrices Draw(&identity, &colorMatrix); Vector::Copy(&pos, &oldPos); Vector::Copy(&scale, &oldScale); halignment = oldHAlign; valignment = oldVAlign; vid.xratio = oldXRatio; vid.yratio = oldYRatio; byte *buffer = (byte*)Z_Malloc(width * height * 3, ZT_STATIC); bglPixelStorei(BGL_PACK_ALIGNMENT, 1); bglReadPixels(0, 0, width, height, BGL_RGB, BGL_UNSIGNED_BYTE, buffer); byte *final = RGBtoLuminance(buffer, width, height); SaveTGA("canvas.tga", final, width, height, 1); Z_Free(buffer); // unbind frame buffer bglBindRenderbuffer(BGL_RENDERBUFFER, 0); bglBindFramebuffer(BGL_FRAMEBUFFER, 0); bglDeleteRenderbuffers(1, &canvasRenderBuffer); bglDeleteFramebuffers(1, &canvasFrameBuffer); bglViewport(0, 0, vid.width, vid.height); 