Question to OpenGL Evaluator

[LangFox]

Hello everyone,
I tried evaluator today, the following is origin code:

:
	GLfloat pfControlPoints[][3] = 
	{
		{-5.0f,  5.0f, 0.0f}, {0.0f,  5.0f, 0.0f}, {5.0f,  5.0f, 0.0f},
		{-5.0f,  0.0f, 0.0f}, {0.0f,  0.0f, 0.0f}, {5.0f,  0.0f, 0.0f},
		{-5.0f, -5.0f, 0.0f}, {0.0f, -5.0f, 0.0f}, {5.0f, -5.0f, 0.0f},
	};
 
	glEnable(GL_MAP1_VERTEX_3);
	glMap1f(GL_MAP1_VERTEX_3, 0.0, 1.0, 3, 9, &pfControlPoints[0][0]);
	glBegin(GL_LINE_STRIP);
	{
		for(i = 0; i < 100; i++)
			glEvalCoord1f((GLfloat)i/100);
	}
	glEnd();

I think the code is right, but it didn't work until I did some change to glMap1f() like this:

glMap1f(GL_MAP1_VERTEX_3, 0.0, 1.0, 3, 8, &pfControlPoints[0][0]);

I don't know why. Could you help me? Thanks in advance!

[Bob]

Check the maximum order your implementation supports; glGetInteger with GL_MAX_EVAL_ORDER. I bet you can't use more than 8 points.

[LangFox]

Yes, that's it!
Thank you.