You are right about your assessment that stimuli positioning should be
done this way:
This is what we have been thought in computer engineering classes at any rate. The positioning should be done in a hierarchical way when drawing multipart scenes. This is not currently the case with every stimulus calling glLoadIdentity().
Just wanted to contribute a little to the discussion.
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 :)
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