Gökhan Sever wrote:
This is technically called OpenGL backend, isn't it?
well, I think it's different -- he's not really using the standard backend API.
The trick with doing a real OpenGL back-end, is that a lot of computation time is spend doing transforms, and that can't be fully pushed to the back-end, because MPL provided arbitrary transforms.
There is also a fair bi tof time spent pushing data to the back-end.
I think to really get the benefit of OpenGL, you'd need the back-end to be semi-perstent -- you'd pass data in, and teh back-end would render it without having to pass the data in again. This would only support transforms that the back-end supports (linear only?). However, I think there could still be areal performance benefit bey breaking the transform pipeline into two parts -- one from arbitrary coordinates to something orthogonal and linear, and then a final one from that to screen coordinates (zooming and panning). Then you'd at least get full hardware accelerated performance for zooming and panning
We're doing this for a high-performance interactive mapping app, and it's working pretty well. However, OpenGL is pretty darn low-level, so there's a lot of code to write!
Christopher Barker, Ph.D.
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