OpenGL won't render with top left coordinates

Question

I got my projection matrix setup with glOrtho() like this:

glOrtho(-Application.HALF_WIDTH, Application.HALF_WIDTH, -Application.HALF_HEIGHT, Application.HALF_HEIGHT, 1, -1);

So, when I draw something at origin (0; 0), opengl draws it at the center of the screen. Fine. But now I want to flip the Y coordinate, so I've changed it to this:

glOrtho(-Application.HALF_WIDTH, Application.HALF_WIDTH, Application.HALF_HEIGHT, -Application.HALF_HEIGHT, 1, -1);

And when I try to draw at (0; 0) (or at any position), it gives a black screen.

What could cause this problem? p.s. i'm using lwjgl

If you have backface culling enabled, note that inverting the y-axis changes the winding order. — BDL, Nov 20 '15 at 20:39
oh, indeed. setting glFontFace(GL_CCW) solved it. thank you! — ibe, Nov 20 '15 at 21:11

score 4 · Accepted Answer · answered Nov 20 '15 at 21:14

4

When changing the orientation of the y-axis, also the winding order of the primitives changes. So if backface culling is enabled, one has to adjust the winding order by setting it with

glFontFace(GL_CCW)

answered Nov 20 '15 at 21:14

BDL

21,052
22
49
55

OpenGL won't render with top left coordinates

1 Answers1