Hi,
I'm using floating point textures as my targets for multipass RTT. In my
tests I have noticed that if three or less camera nodes are set up using
GL_RGBA16F_ARB internal format textures, the frame rate stays at a constant
75FPS when only the texture is rendered to the screen (i.e. the texture is
rendered over the full window).
If I add an additional camera node, the frame rate drops to 15 FPS. Five
nodes yields 8FPS, and 5FPS are achieved with six nodes. Also, if I set
the texture to render to 1/4 of the screen and position the main camera so
that the actual scene being rendered to texture is visible, I'll get 25FPS
for the three camera node implementation.
I'm setting up my textures with internal formats of GL_RGBA16F_ARB, a
source type of GL_FLOAT, and a source format of GL_RGBA.
The FBO is set up like:
fbo->setAttachment(GL_COLOR_ATTACHMENT0_EXT,
osg::FrameBufferAttachment(texture));
fbo->setAttachment(GL_DEPTH_ATTACHMENT_EXT,
osg::FrameBufferAttachment(new osg::RenderBuffer(512, 512,
GL_DEPTH_COMPONENT24)));
My min/max filters are set up as NEAREST.
If I change my textures to internal formats of GL_RGBA and the source type
as GL_UNSIGNED_BYTE, my performance is great.
Any thoughts?
Thanks,
Brian
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