I think you're probably right about this. I'm entirely self-taught in
OpenGL, and I never came across the arguments you presented, although
they seem entirely logical. I've gone ahead and made a few
modifications to VisionEgg.Core to do what you propose, and everything
seems to work fine.
I've put a copy of the new source code here:
The bug I discovered last week was that changes to the modelview matrix state would, against the above stated policy, cause other stimuli to draw wrongly. So, I updated those builtin stimuli which modified it to restore it after use. If we want to live by the documentation as written, my approach is just a workaround, and I need to fix all stimuli to be insensitive to the state of the modelview matrix when their draw() method is called.
The modelview matrix state is an aspect that I just stumbled onto, and I found something somewhat worrisome.
http://www.opengl.org/resources/faq/technical/viewing.htm (section 8.030) http://sjbaker.org/steve/omniv/projection_abuse.html
These both seem to say that all of the camera movements should be taking place in the modelview matrix and not the projection matrix. This came up when I started using my custom-made viewport that does the mapping for our screen. It involves several camera modifications to capture views at different perspectives. I put a Model3DS into the scene and put it on a circular path to make sure that it properly moves from camera to camera, only to find that it showed up in every camera at the same time.
I *think*, after preliminary analysis, that a simple yet tedious modification would fix this problem without modifying existing behaviour. I'm willing to put the time into making this modification assuming that it's deemed a legitimate concern. I think that if we were to modify every stimulus and remove the glLoadIdentity(), and then in the Viewport class wrap stimulus.draw() with a glPushMatrix() and glPopMatrix(), it would be possible to do everything as we are right now without having to modify the GL_PROJECTION matrix to point the camera.
Any thoughts? This may not be a complete analysis... I've just spent an hour or two tracing through (mostly my) code to figure out what the problem is. As I said before though, I'm not adverse to testing and fixing this problem myself. I've used the library a fair bit this summer already and I'd love to contribute back :)
Tony ====================================== The Vision Egg mailing list Archives: http://www.freelists.org/archives/visionegg Website: http://www.visionegg.org/mailinglist.html
-- Andrew D. Straw Post-doctoral scholar ,-. Dickinson Lab \_/ California Institute of Technology 8||} Mailcode 138-78 / \ Pasadena CA 91125, USA `-^ email: astraw@xxxxxxxxxxx office: +1 626 395 4396
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