glutReshapeFunc

OpenGL OpenGL: Basic Coding
1

I have a small OpenGL program that displays a small square in a window. When I add the glutReshapeFunc to the program it crashes at the call to glutMainLoop.

2

You need to post the code, without seeing what you are doing we have no clue as to what is causing the crash.

Originally posted by bagiles:
[b]I have a small OpenGL program that displays a small square in a window. When I add the glutReshapeFunc to the program it crashes at the call to glutMainLoop.

[/b]

3

#include <gl\glut.h>

void RenderScene(void)
{
glClear(GL_COLOR_BUFFER_BIT);

glColor3f(1.0f,0.0f,0.0f);

glRectf(100.0f,150.0f,150.0f,100.0f);

glFlush();

}

void SetupRC(void)
{
glClearColor(0.0f,0.0f,0.0f,1.0f);
}

void ChangeSize(GLsizei w, GLsizei h)
{
//prevent divide by zero
if(h==0)
h=1;

//set viewport to window dimensions
glViewport(0,0,w,h);

//Reset corrdinate system
glMatrixMode(GL_PROJECTION);
glLoadIdentity();

//Establish clipping volume (left,right,bottom,near,far)
if(w&lt;=h)
	glOrtho(0.0f,250.0f,0.0f,250.0f*h/w,1.0f,-1.0f);
else
	glOrtho(0.0f,250.0f*w/h,0.0f,250.0f,1.0f,-1.0f);

glMatrixMode(GL_MODELVIEW);
glLoadIdentity();

}

int main(void)
{
glutInitDisplayMode(GLUT_SINGLE | GLUT_RGB);
glutCreateWindow(“Simple”);
glutDisplayFunc(RenderScene);
glutReshapeFunc(ChangeSize);

SetupRC();

glutMainLoop();

return 0;

}

4

Don’t you have to size the window initially?

glutInitDisplayMode(GLUT_SINGLE | GLUT_RGB);

glutInitWindowSize(width,height);

glutCreateWindow(“Simple”);
glutDisplayFunc(RenderScene);
glutReshapeFunc(ChangeSize);

I think entering in the initial size might help. Otherwise you could get a divide by 0 on line :

glOrtho(0.0f,250.0f,0.0f,250.0f*h/w,1.0f,-1.0f);

because if w and h = 0 this line is run. Only the divide by 0 for h was taken care of with:

//prevent divide by zero
if(h==0)
h=1;

See if that works.

5

What’s that SetupRC thing? Throw it away, it’s certainly not needed with glut and might interfere!

6

zeckensack,
SetupRC is ok. Thats how examples are done in the OpenGL Superbible. Shouldn’t be a problem here.