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yossi
12-30-2007, 09:01 AM
Hello guys,

I wrote a small tutorial for myself that renders a triangle with FSAA. I have the NVIDIA FX 5700. I use GLFW (do all the windows stuff) to define a rendering buffer with say 16 samples per fragment.
When I render the trig I do see smoothing along the trig's edges with the backgroung. The problem is that I can't turn off the multi sampling rendering by calling glDisable(GL_MULTISAMPLE_ARB).
It seems that glEnable/glDisable with GL_MULTISAMPLE_ARB dosen't work. Once the multisample buffer is defined, I can't return to normal rendering.
Do I miss something trivial?
Thanks

Dark Photon
12-31-2007, 10:23 AM
FSAA...NVIDIA FX 5700...GLFW...16 samples per fragment...I do see smoothing along the trig's edges...problem is that I can't turn off the multi sampling rendering by calling glDisable(GL_MULTISAMPLE_ARB)....Once the multisample buffer is defined, I can't return to normal rendering.
I too would like some clarification on how exactly this works. For instance:

http://people.freebsd.org/~rhh/opengl/msaa_confusion.gif

(Note: scroll right; above pic contains 3 sub-images)

This is with the latest NVidia drivers (169.07) on Linux on a GeForce 6800. __GL_FSAA_MODE=0 is FSAA disabled, whereas 4 is 4x Bilinear Multisampling. All were rendered to a window allocated in a 4X MSAA visual.

It appears that glDisable( GL_MULTISAMPLE ) only disables multisample "rasterization" (as the spec says) but it does not disable multisample "downsample filtering". Is this correct? And are there any OpenGL-defined controls for modifying the latter?

Don't think so, but I wanted to double-check.

yossi, I don't know if this is your original question, but if not please clarify.

yossi
01-01-2008, 06:55 AM
Thanks Dark photon for your reply and HNY to you,

I get more or less what you have sent as images. When disabled and GL_FSA_MODE is 4, still there is smoothing of the edges. I thought I would get no smoothing at all like in the left image
(?!)