glDrawElements + Vertex Array + High Polycount = No Lighting?

OpenGL Development JOGL Development
#1

When I use glDrawElements on a model with a really high polygon count, opengl lighting stops working. This doesn’t happen if I use glDrawArrays, or if I use vertex buffer objects.

http://people.umass.edu/eraboin/elements.jpg

http://people.umass.edu/eraboin/arrays.jpg

The left picture is with glDrawElements, the right is with glDrawArrays. This only happens if the model has more than ~1500 vertices, but that’s not really a stable number. I want to know what’s causing this so I can avoid it in my program… but I want to keep using glDrawElements, and provide support for cards that can’t use vertex buffer objects.

#2

Have you tried installing the DebugGL pipeline in your GLEventListener.init() method (see the Gears and other demos’ source code for examples)? Does it report any errors? I would guess you may be handing invalid indices to glDrawElements.

#3

I have drawable.setGL(new DebugGL(drawable.getGL())); in the init() method of my GLEventListener. I don’t get any error messages.

However, since you brought it up, this is what the Gears demo looks like on my computer:

http://people.umass.edu/eraboin/gears.jpg

… notice the lack of lighting around the edges.

I’m using JOGL 1.1 b12, under WinXP SP1. I’ve got a Radeon 9800 PRO, with Omega drivers installed.

If it turns out that my computer is just acting strange, that’s actually ok. Because I can test it with VBOs instead, as long as vertex arrays will work for other users when they try it.

#4

My guess is that it’s a bug in the Omega drivers.