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heefan
12-18-2008, 11:09 PM
Hi all, I am new on OpenGL, and reading 'OpenGL Super Bible 4th' now.

In the chapter 2 (Page 54), I run the sample code, but I got different result from the book. Actually I didn't get rectangle.

The source code like this:



#include "gltools.h"
#include "math3d.h"

void RenderScene(void)
{
// Clear the window with current clearing color
glClear(GL_COLOR_BUFFER_BIT);
// Set current drawing color to red
// R G B
glColor3f(1.0f, 0.0f, 0.0f);
// Draw a filled rectangle with current color
glRectf(-25.0f, 25.0f, 25.0f, -25.0f);
// Flush drawing commands
glFlush();
}


///////////////////////////////////////////////////////////
// Set up the rendering state
void SetupRC(void)
{
// Set clear color to blue
glClearColor(0.0f, 0.0f, 1.0f, 1.0f);
}


///////////////////////////////////////////////////////////
// Called by GLUT library when the window has chanaged size
void ChangeSize(GLsizei w, GLsizei h)
{
GLfloat aspectRatio;
// Prevent a divide by zero
if(h == 0)
h = 1;
// Set Viewport to window dimensions
glViewport(0, 0, w, h);
// Reset coordinate system
glMatrixMode(GL_PROJECTION);
glLoadIdentity();
CHAPTER 2 Using OpenGL 54LISTING 2.2 Continued
// Establish clipping volume (left, right, bottom, top, near, far)
aspectRatio = (GLfloat)w / (GLfloat)h;

if (w <= h)
glOrtho (-100.0, 100.0, -100 / aspectRatio, 100.0 / aspectRatio, 1.0, -1.0);

else
glOrtho (-100.0 * aspectRatio, 100.0 * aspectRatio,
-100.0, 100.0, 1.0, -1.0);
glMatrixMode(GL_MODELVIEW);
glLoadIdentity();
}


///////////////////////////////////////////////////////////
// Main program entry point
void main(void)
int main(int argc, char* argv[])
{
glutInit(&amp;argc, argv);
glutInitDisplayMode(GLUT_SINGLE | GLUT_RGB);
glutCreateWindow(“GLRect”);
glutDisplayFunc(RenderScene);
glutReshapeFunc(ChangeSize);
SetupRC();
glutMainLoop();
return 0;
}


The function of the program is to draw a rectangle.

Is the code wrong?