One of the largest performance hits I take is with lines.  Even using the direct OpenGL commands for a line, really drags down the fps when your talking about 20,000+ lines.

Code:

gl.glBegin(gl.GL_LINES);
gl.glColor4f(red(c), green(c), blue(c), linealpha);
gl.glVertex3f(x,y,z); //creates line
gl.glVertex3f(x,y,z);
gl.glEnd();
 

I've had no such performance loss using textures on a quad.  I've loaded up 500,000+ textured quads without much performance loss.  Is there any way to create a line using a texture in OpenGL, perhaps a rectangle quad?

I wrap the code in a display list.

Ok, but how would I apply a texture to it?  Could you give an example?  What would the size of the image for stretching (or repeating) it across the defined line space.  Interesting thought on the triangle!  I've tried VBO's before and did not see any increase but am willing to give it a try.  The main performance issue seemed to be in creating the lines themselves, and not how I called it, but I'm open to whatever to get it to perform better.