We are developing software for slide show creation and use OpenGL. We use FBO + PBO for fast data reading from VGA to RAM but on some video cards from ATI we faced with the following problems:
- swapping RGB components
- pixel shifting
There are no problems if we do not use PBO. Also we have noticed that the aspect ratio of PBO/FBO (4:3) solve the pixel shifting problem.
Any thoughts or suggestions?
Here are more details:
- ATI Radeon HD 3650
PBO code:
public bool PBO_Initialize(
int bgl_size_w,
int bgl_size_h)
{
PBO_Release();
if (mCSGL12Control1 != null)
{
GL mGL = mCSGL12Control1.GetGL();
mCSGL12Control1.wgl_MakeCurrent();
//
// check PBO is supported by your video card
if (mGL.bglGenBuffersARB == true &&
mGL.bglBindBufferARB == true &&
mGL.bglBufferDataARB == true &&
mGL.bglBufferSubDataARB == true &&
mGL.bglMapBufferARB == true &&
mGL.bglUnmapBufferARB == true &&
mGL.bglDeleteBuffersARB == true &&
mGL.bglGetBufferParameterivARB == true)
{
mGL.glGenBuffersARB(2, _pbo_imageBuffers);
int clientHeight1 = bgl_size_h / 2;
int clientHeight2 = bgl_size_h - clientHeight1;
int clientSize1 = bgl_size_w * clientHeight1 * 4;
int clientSize2 = bgl_size_w * clientHeight2 * 4;
mGL.glBindBufferARB(GL.GL_PIXEL_PACK_BUFFER_ARB, _pbo_imageBuffers[0]);
mGL.glBufferDataARB(GL.GL_PIXEL_PACK_BUFFER_ARB, clientSize1, IntPtr.Zero,
GL.GL_STREAM_READ_ARB);
mGL.glBindBufferARB(GL.GL_PIXEL_PACK_BUFFER_ARB, _pbo_imageBuffers[1]);
mGL.glBufferDataARB(GL.GL_PIXEL_PACK_BUFFER_ARB, clientSize2, IntPtr.Zero,
GL.GL_STREAM_READ_ARB);
return true;
}
}
return false;
}
... PBO read data back to memory
int clientHeight1 = _bgl_size_h / 2;
int clientHeight2 = _bgl_size_h - clientHeight1;
int clientSize1 = _bgl_size_w * clientHeight1 * 4;
int clientSize2 = _bgl_size_w * clientHeight2 * 4;
//mGL.glPushAttrib(GL.GL_VIEWPORT_BIT | GL.GL_COLOR_BUFFER_BIT);
// Bind two different buffer objects and start the glReadPixels
// asynchronously. Each call will return directly after
// starting the DMA transfer.
mGL.glBindBufferARB(GL.GL_PIXEL_PACK_BUFFER_ARB, _pbo_imageBuffers[0]);
mGL.glReadPixels(0, 0, _bgl_size_w, clientHeight1, imageFormat,
pixelTransferMethod, IntPtr.Zero);
mGL.glBindBufferARB(GL.GL_PIXEL_PACK_BUFFER_ARB, _pbo_imageBuffers[1]);
mGL.glReadPixels(0, clientHeight1, _bgl_size_w, clientHeight2, imageFormat,
pixelTransferMethod, IntPtr.Zero);
//mGL.glPopAttrib();
mGL.glBindFramebufferEXT(GL.GL_FRAMEBUFFER_EXT, 0);
// Process partial images. Mapping the buffer waits for
// outstanding DMA transfers into the buffer to finish.
mGL.glBindBufferARB(GL.GL_PIXEL_PACK_BUFFER_ARB, _pbo_imageBuffers[0]);
IntPtr pboMemory1 = mGL.glMapBufferARB(GL.GL_PIXEL_PACK_BUFFER_ARB,
GL.GL_READ_ONLY_ARB);
mGL.glBindBufferARB(GL.GL_PIXEL_PACK_BUFFER_ARB, _pbo_imageBuffers[1]);
IntPtr pboMemory2 = mGL.glMapBufferARB(GL.GL_PIXEL_PACK_BUFFER_ARB,
GL.GL_READ_ONLY_ARB);
System.Runtime.InteropServices.Marshal.Copy(pboMemory1, _bgl_rgbaData_out, 0, clientSize1);
System.Runtime.InteropServices.Marshal.Copy(pboMemory2, _bgl_rgbaData_out, clientSize1, clientSize2);
// Unmap the image buffers
mGL.glBindBufferARB(GL.GL_PIXEL_PACK_BUFFER_ARB, _pbo_imageBuffers[0]);
mGL.glUnmapBufferARB(GL.GL_PIXEL_PACK_BUFFER_ARB);
mGL.glBindBufferARB(GL.GL_PIXEL_PACK_BUFFER_ARB, _pbo_imageBuffers[1]);
mGL.glUnmapBufferARB(GL.GL_PIXEL_PACK_BUFFER_ARB);
FBO initialization
private static void FBO_Initialize(GL mGL,
ref int[] bgl_texture,
ref int[] bgl_framebuffer,
ref int[] bgl_renderbuffer,
ref byte[] bgl_rgbaData,
int bgl_size_w,
int bgl_size_h)
{
// Texture
mGL.glGenTextures(1, bgl_texture);
mGL.glBindTexture(GL.GL_TEXTURE_2D, bgl_texture[0]);
mGL.glTexParameteri(GL.GL_TEXTURE_2D, GL.GL_TEXTURE_MAG_FILTER, GL.GL_NEAREST);
mGL.glTexParameteri(GL.GL_TEXTURE_2D, GL.GL_TEXTURE_MIN_FILTER, GL.GL_NEAREST);
mGL.glTexParameteri(GL.GL_TEXTURE_2D, GL.GL_TEXTURE_WRAP_S, GL.GL_CLAMP_TO_EDGE);
mGL.glTexParameteri(GL.GL_TEXTURE_2D, GL.GL_TEXTURE_WRAP_T, GL.GL_CLAMP_TO_EDGE);
IntPtr null_ptr = new IntPtr(0);
// <null> means reserve texture memory, but texels are undefined
mGL.glTexImage2D(GL.GL_TEXTURE_2D, 0, GL.GL_RGBA, bgl_size_w, bgl_size_h, 0, GL.GL_RGBA, GL.GL_UNSIGNED_BYTE, null_ptr);
//
mGL.glGenFramebuffersEXT(1, bgl_framebuffer);
mGL.glBindFramebufferEXT(GL.GL_FRAMEBUFFER_EXT, bgl_framebuffer[0]);
mGL.glGenRenderbuffersEXT(1, bgl_renderbuffer);
mGL.glBindRenderbufferEXT(GL.GL_RENDERBUFFER_EXT, bgl_renderbuffer[0]);
mGL.glRenderbufferStorageEXT(GL.GL_RENDERBUFFER_EXT, GL.GL_DEPTH_COMPONENT24, bgl_size_w, bgl_size_h);
mGL.glFramebufferTexture2DEXT(GL.GL_FRAMEBUFFER_EXT, GL.GL_COLOR_ATTACHMENT0_EXT,
GL.GL_TEXTURE_2D, bgl_texture[0], 0);
mGL.glFramebufferRenderbufferEXT(GL.GL_FRAMEBUFFER_EXT, GL.GL_DEPTH_ATTACHMENT_EXT,
GL.GL_RENDERBUFFER_EXT, bgl_renderbuffer[0]);
// Errors?
int status = mGL.glCheckFramebufferStatusEXT(GL.GL_FRAMEBUFFER_EXT);
if (status != GL.GL_FRAMEBUFFER_COMPLETE_EXT || mGL.glGetError() != GL.GL_NO_ERROR)
{
mGL.glFramebufferTexture2DEXT(GL.GL_FRAMEBUFFER_EXT, GL.GL_COLOR_ATTACHMENT0_EXT,
GL.GL_TEXTURE_2D, 0, 0);
mGL.glFramebufferRenderbufferEXT(GL.GL_FRAMEBUFFER_EXT, GL.GL_DEPTH_ATTACHMENT_EXT,
GL.GL_RENDERBUFFER_EXT, 0);
mGL.glBindTexture(GL.GL_TEXTURE_2D, 0);
mGL.glDeleteTextures(1, bgl_texture);
mGL.glBindRenderbufferEXT(GL.GL_RENDERBUFFER_EXT, 0);
mGL.glDeleteRenderbuffersEXT(1, bgl_renderbuffer);
mGL.glBindFramebufferEXT(GL.GL_FRAMEBUFFER_EXT, 0);
mGL.glDeleteFramebuffersEXT(1, bgl_framebuffer);
throw new Exception("Bad framebuffer.");
}
mGL.glDrawBuffer(GL.GL_COLOR_ATTACHMENT0_EXT);
mGL.glReadBuffer(GL.GL_COLOR_ATTACHMENT0_EXT); // For glReadPixels()
mGL.glBindFramebufferEXT(GL.GL_FRAMEBUFFER_EXT, 0);
mGL.glDrawBuffer(GL.GL_BACK);
mGL.glReadBuffer(GL.GL_BACK);
mGL.glBindTexture(GL.GL_TEXTURE_2D, 0);
bgl_rgbaData = new byte[bgl_size_w * bgl_size_h * 4];
}
