glOrtho() Mirror Image

OpenGL OpenGL: Basic Coding
1

Hello,

I am using glOrtho command to set the camera viewing positions for my opengl window in QT, I need to make center of the screen as orgin.But, when I load any texture on GL window it appears like mirror Image. I am doing as below.

glViewport(0.0f, 0.0f, 650, 800);
glMatrixMode(GL_PROJECTION);
glLoadIdentity();
glOrtho(-325 , 325, -350, 250, -15, 15);
glMatrixMode(GL_MODELVIEW);

when I change the glOrtho statement to
glOrtho(-325 , 325, 250, -350, -15, 15); it works, I mean texture would be shown normally. But I know there is something wrong because this is against specification of glOrtho().

How to set the view origin to center without effecting on other primitives or textures?

2

It isn’t against the specification.

you call
glMatrixMode(GL_PROJECTION);
glLoadIdentity();
glOrtho(-325 , 325, -350, 250, -15, 15);

after you are done rendering your quad with that texture.

3

I bet that the problem is not in the projection but in the way you map the texture!

Change t-koordinates of the vertices and everything will be just fine. :wink:

4

Yes Thank you Aleksandar! you are right…
I am using glTexCoord2d() with wrong quadrants.
Thanks for the link V-man, Now I have to explore about the GLU stuff
Thanks Again!