🔒 Locked

[OpenGL] Render using buffer.

Started by inbgche Apr 24, 2006 at 7:06 AM 2 replies 850+ views

Original Post

Apr 24, 2006 at 7:06 AM

Is there any method that I save current frame buffer and render the buffer instead of full 3D scene in OpenGL. Because my scene do not change and it do not need any update, so I think if I can save my current frame buffer, and render using the buffer by just 2D rendering, performance will rise up dramatically. But, I didn't find the way. I read some function's decriptions, glCopyPixels(), glDrawPixels(). Unfortunately I didn't catch how can I make it using that functions. Any comments please...

IvanMilles

Apr 24, 2006 at 7:25 AM

GLint index;
glGenTextures (1, &index);
glBindTexture (GL_TEXTURE_2D, index);
glCopyTexImage2D (GL_TEXTURE_2D, 0, GL_RGB, 0, 0, winW, winH, 0);

Now index is a texture that contains your scene (provided that the scene is a power-of-two thing, otherwise you'll have to mess around a bit to do it).

But, if your scene isn't changing, why re-display it? Only re-render when something has changed in your scene. :)

taby

1,513

taby

Apr 24, 2006 at 7:38 AM

glGenRenderbuffersEXT can be used to create a specialized offscreen render buffer. I use this for the same purpose you do.

Here is a list of the related functions:
glBindFramebufferEXT;
glDeleteFramebuffersEXT;
glGenFramebuffersEXT;
glFramebufferTexture2DEXT;
glBindRenderbufferEXT;
glDeleteRenderbuffersEXT;
glGenRenderbuffersEXT;
glRenderbufferStorageEXT;
glFramebufferRenderbufferEXT;

The reason to redisplay the 2D buffer is so that any areas of the screen which may have been drawn over by the OS can be refreshed in a non-OS-specific way.

Tatsunami

Apr 24, 2006 at 7:42 AM

If you have a relatively-recent video card, the shiny new solution these days is to use the EXT_framebuffer_object extenstion.

This extension allows you to render the scene directly to a texture without needing any of the glCopy* functions.

Topic Locked

This topic has been locked by a moderator. New replies are not allowed.