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glortho function - assistance required...


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#1 chilun   Members   -  Reputation: 122

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Posted 25 October 2013 - 03:50 AM

Hi all;

 

I have some trouble with trying to use the glOrtho function to scale some graphics to a window (height - 500, width - 500).

I've created a function called reshape to do this, but for some reason I think my numbers are off as the graphics are scaling to the size I would like, but for some reason it is only scaling into the top-left hand corner of the window - I want to make sure that the scaling fills the entire size of the window. Can anyone provide any tips on what I can do?

 

Thank you

...void reshape(int w, int h)
{
glViewport(0,0, w, h);
GLfloat aspect = (GLfloat)w / (GLfloat) h;
glMatrixMode (GL_PROJECTION);
glLoadIdentity();
glOrtho(0.0f, w, h, 0.0f, 0.0f, 1.0f);
}
...


int main (int argc, char **argv)
{

...
glutInitWindowSize(500, 500);
glutReshapeFunc(reshape);
...
}


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#2 Goran Milovanovic   Members   -  Reputation: 1103

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Posted 26 October 2013 - 11:50 PM

Try:

 

GLfloat x = w / 2;
GLfloat y = h / 2;
glOrtho(-x, x, -y, y, -1.0f, 1.0f);

 

Scaling the projection matrix will scale everything in the scene. If you just want to scale a specific object, you should do so by scaling its world transform matrix.

 

... Is the example small enough to post somewhere? That would help.


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#3 chilun   Members   -  Reputation: 122

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Posted 28 October 2013 - 05:19 PM

Hi Goran;

 

I'll definitely try what you suggested and will come back to you with a response.

 

Thank you very much indeed :)






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