glDrawElements()

[Unregistered]

Hi guys, a little help required with glDrawElements().
I can't for the life of me get it to draw anything, heres some code I am using

void display( void )
{
	GLuint indices[] = { 50, 50,
		             50, 70,
			     70, 70,
			     70, 50 };
	
	glClear( GL_COLOR_BUFFER_BIT );
	glPushMatrix();

	glColor3f( 1.0, 1.0, 1.0 );

	glEnableClientState( GL_VERTEX_ARRAY );
	glVertexPointer( 2, GL_INT, 0, indices );

	glDrawElements( GL_POLYGON, 8, GL_UNSIGNED_INT, indices );
	glDisableClientState( GL_VERTEX_ARRAY );
	
	glPopMatrix();
	glutSwapBuffers();
}

In the opengl red book it states that the type argument for glDrawElements() should be GL_UNSIGNED_BYTE, GL_UNSIGNED_SHORT or GL_UNSIGNED_INT.
However it also states that the type argument for glVertexPointer() should be GL_SHORT, GL_INT, GL_FLOAT or GL_DOUBLE. No unsigned type!!!
So, do you not need glVertexPointer() when using glDrawElements()? I tried it and that didn't work either.
Any comments would be great.

[no-one]

ask here http://www.opengl.org they can solve this faster than i can.

[C_Coder]

For those interested the answer is that glDrawElements needs 2 array's, the vertex array and the index array. You pass the index array to glDrawElements not the vertex array

GLfloat vertexs[] = { 25.0, 25.0,
                      25.0, 75.0,
		      75.0, 75.0,
		      75.0, 25.0 };

GLubyte indices[] = { 0, 1, 2, 3 };

glEnableClientState( GL_VERTEX_ARRAY );
glEnableClientState( GL_INDEX_ARRAY );

glIndexPointer( GL_UNSIGNED_BYTE, 0, indices );
glVertexPointer( 2, GL_FLOAT, 0, vertexs );

glDrawElements( GL_QUADS, 4, GL_UNSIGNED_BYTE, indices );

The index array specifies which order to use the vertices in so you could do

GLfloat vertexs[] = { 25.0, 25.0,
                      25.0, 75.0,
		      75.0, 75.0,
		      75.0, 25.0 };

GLubyte indices[] = { 1, 2, 3 };

glEnableClientState( GL_VERTEX_ARRAY );
glEnableClientState( GL_INDEX_ARRAY );

glIndexPointer( GL_UNSIGNED_BYTE, 0, indices );
glVertexPointer( 2, GL_FLOAT, 0, vertexs );

glDrawElements( GL_TRIANGLES, 3, GL_UNSIGNED_BYTE, indices );

Which only uses 3 of the vertices and draws a triangle.

[Ti22]

I found this very useful, I got my array to draw the points I want.

thx alot.