View Full Version : Changing Implementation-Dependent State Variables

07-22-2003, 08:10 AM
Is there any way to change the values of implementation dependent state variables.

Specifically, I wish to set a value for 'GL_MAX_EVAL_ORDER'. I need to do this because I want to render bezier curves with more than 8 control points. (output from ATT's graphViz tool)


07-22-2003, 10:28 PM
Those are not variables, but rather constants telling you how much the max are in the implementation, you cannot change those and the HW/driver cant handle any bigger number than what you get..

For bezier curves you can easily calculate this in the cpu instead.

07-23-2003, 02:03 AM
This is a common misunderstanding of the meaning of eval ORDER and NUMBER of control points!

You can evaluate as many control points as you want. You only need to map a subset needed for the desired order and step over your control grid in multiple steps.
You actually don't want to evaluate a polynome of 8's order most of the time.
Quadratic or cubic interpolation might be sufficient for most cases.
Hmm, you might have to take care which (s, t) are evaluated to get the second derivative continuos.