glPrimitiveRestartIndex()

OpenGL OpenGL: Advanced Coding
1

Hi ,
I am trying to use glPrimitiveRestartIndex() to draw GL_LINES. Here is code :

const GLfloat data[] =
{
-0.9f, -0.6f,
-0.9f, -0.9f,
-0.6f, -0.9f,
-0.6f, -0.6f,

		-0.3f,-0.6f, 
		-0.3f,-0.9f, 
		0.0f,-0.9f,
		0.0f,-0.6f
    };

   GLuint  indices [] = {0, 1, 2, 3 ,666,  4 , 5 ,6 , 7 };

glPrimitiveRestartIndex(666);
glDrawElements(GL_LINES, 9 , GL_UNSIGNED_INT ,(GLvoid *)0);

Now, with this code it draws only 3 parallel lines instead of 4.
But when i increase the count in glDraw to 10, it draws 4 lines correctly. Is it what expected?
When i replace GL_LINES with GL_TRIANGLE_FAN with count=9, it correctly draws 2 quads.

Please let me know where i am going wrong.

Thanks in advance,

2

LINES is not a strip primitive that needs broken. It’s automatically broken every 2 verts. Why are you combining these? If you’re just trying to support a wireframe mode, would:

glPolygonMode ( GL_FRONT_AND_BACK, do_wireframe ? GL_LINE : GL_FILL );

work just as well?

That said, not sure why what you’re doing (LINES+restart) shouldn’t work. I don’t recall any language that limits the use of restart based on primitive type. Probably just a hardly if ever used combination.

3

Sigh - cross-post: glPrimitiveRestartIndex() - OpenGL: Basic Coding - Khronos Forums