OpenGL perspective problem

Graphics and GPU Programming Programming OpenGL

Started by assainator January 31, 2012 06:32 PM

6 comments, last by Nick of ZA 11 years, 9 months ago

685

Author

January 31, 2012 06:32 PM

Hello all,

I'm working on a OpenGL project but I'm having troubles with the perspective. The meshes appear to be scaled up on the x-axis.
In the image below, you can see a sphere that is supposed to be, well, a sphere, round. Obviously it's not. What causes this behavior?

Thanks in advance.

"What? It disintegrated. By definition, it cannot be fixed." - Gru - Dispicable me

"Dude, the world is only limited by your imagination" - Me

Brother Bob

10,350

January 31, 2012 06:41 PM

Likely an incorrect aspect ratio. That is, your projection assumes the width and the height of the window are the same, but in reality the window is wider, and so the image looks stretched.

themean

1,339

January 31, 2012 06:42 PM

which opengl you use
if you use 2.1 may be i can help
i think your window is stretched and you dont calculate this

SaTANO

507

January 31, 2012 06:46 PM

your projection matrix is not properly set for your rendering viewport

check glViewPort(x,y,width,height) for aspect ratio (you are probably not rendering 1:1)
than set/create projection matrix for correct values

assainator

685

Author

January 31, 2012 06:56 PM

I'm using OGL 2.0.

My code is:



glMatrixMode(GL_PROJECTION);

glLoadIdentity();

glViewport(0,0, Resolution.x, Resolution.y);

gluPerspective(90, (Resolution.x / Resolution.y), 1.0f, 5000.0f);

glMatrixMode(GL_MODELVIEW);

"What? It disintegrated. By definition, it cannot be fixed." - Gru - Dispicable me

"Dude, the world is only limited by your imagination" - Me

21st Century Moose

13,459

January 31, 2012 07:27 PM

Are resolution.x and resolution.y ints? If so you'll always* get an aspect of 1 when you divide them. Cast them to floats instead.

[size=1]*: Unless height is greater than width, of course.

Direct3D has need of instancing, but we do not. We have plenty of glVertexAttrib calls.

assainator

685

Author

January 31, 2012 08:50 PM

Are resolution.x and resolution.y ints? If so you'll always* get an aspect of 1 when you divide them. Cast them to floats instead.

[size=1]*: Unless height is greater than width, of course.

Sometimes I just do not understand how I don't notice that kind of simple problems....

That, off course, fixed the problem.