[Mesa3d-users] Unexpected: Mesa faster than nVidia OpenGL

[Robert B. <ro...@sc...>]

Hi,

A student of mine stumbled upon something I can not explain.
I am hoping someone on this list can help us.

He has written a Vtk program that extracts an isosurface
from a stack of medical images and renders the result on
screen.

While measuring performance, I asked him to make a
comparison between Mesa (5.0.1) and the hardware accelerated
OpenGL drivers (nVidia 1.0-4363).

To my suprise, it takes Mesa 2 seconds to render the first
image, the nVidia drivers take 44 seconds! The number of
triangles is exactly the same (roughly 0.5 million), the
rendered images are almost the same (to the extend one would
expect with different rendering engines) and the results are
reproducable on other machines.

When interacting with the image (i.e. rotating, scaling,
etc.), the nVidia drivers are clearly faster than Mesa.
Still; I'm puzzled by this huge difference in the first
image.

Does anybody have any clue why this is?

Thanks,
-- Rob

-- 
[] Robert Belleman, PhD    X  Faculty of Science, Informatics Inst.    []
[] ro...@sc...  |X| University of Amsterdam, the Netherlands []
[] tel: (+31) 20 525 7510  X  http://www.science.uva.nl/~robbel/       []