View Full Version : Draw a square?
05-02-2011, 10:12 AM
Hi, I try to draw a square but I have the problem which can be see and the images. Can someone explain me why?
I use GL_QUADS.
05-02-2011, 10:26 AM
It looks like you are drawing the vertices in the wrong order. You need to keep an orientation. Can you post your draw code here?
05-02-2011, 10:36 AM
05-02-2011, 10:42 AM
As I said, it is in the wrong order.
// change coord 3 with 4.
BTW, why homogeneous coords are set to 0.0f? It shouldn't be 1.0f?
05-02-2011, 10:45 AM
Ok, it works! Thank you!
I try with 0.0f and 1.0f and I don't see any difference, so I prefer with 0.0f because it's easier to read.
05-02-2011, 11:13 AM
It is odd. Using 0.0 as the homogeous coordinates gives you a vector instead of a point. Maybe, when you are drawing, you are ignoring the fourth coordinate. In order to have project points on screen, OpenGL divides x,y and z by the w value, if it is different from 0.
05-02-2011, 12:05 PM
In my code I write:
It has been copied from a code on Internet
Now I put glVertexPointer(4,GL_FLOAT,4*sizeof(GL_FLOAT),0);
with the w value to 1.0f.
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