How to Enable Texture Coordinate Generation with the OpenGL API

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Texture coordinate generation is not a good idea unless you are looking
for specific effects that cannot be duplicated when setting your own
texture coordinates. Generally people steer clear of this, but I will show
you how to use it anyway.

To enable texture coordinate generation, simply call:
glEnable(GL_TEXTURE_GEN_S);

And were done. Extremely simple, there are also
GL_TEXTURE_GEN_R
GL_TEXTURE_GEN_T
GL_TEXTURE_GEN_Q
but they would be used when looking for different effects

In this tutorial I am uing S and T.

And that is it, if you have any questions please email me at swiftless@gmail.com

#include <GL/gl.h>
#include <GL/glut.h>
#include <windows.h>
#include <stdio.h>

GLuint texture; //the array for our texture

GLfloat angle = 0.0;

GLuint LoadTexture( const char * filename, int width, int height )
{
   GLuint texture;
   unsigned char * data;
   FILE * file;

   //The following code will read in our RAW file
   file = fopen( filename, "rb" );
   if ( file == NULL ) return 0;
   data = (unsigned char *)malloc( width * height * 3 );
   fread( data, width * height * 3, 1, file );
   fclose( file );

   glGenTextures( 1, &texture ); //generate the texture with the loaded data
   glBindTexture( GL_TEXTURE_2D, texture ); //bind the texture to it's array
   glTexEnvf( GL_TEXTURE_ENV, GL_TEXTURE_ENV_MODE, GL_MODULATE ); //set texture environment parameters

   //here we are setting what textures to use and when. The MIN filter is which quality to show
   //when the texture is near the view, and the MAG filter is which quality to show when the texture
   //is far from the view.

   //The qualities are (in order from worst to best)
   //GL_NEAREST
   //GL_LINEAR
   //GL_LINEAR_MIPMAP_NEAREST
   //GL_LINEAR_MIPMAP_LINEAR

   //And if you go and use extensions, you can use Anisotropic filtering textures which are of an
   //even better quality, but this will do for now.
   glTexParameterf( GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR_MIPMAP_LINEAR );
   glTexParameterf( GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR_MIPMAP_LINEAR );

   //Here we are setting the parameter to repeat the texture instead of clamping the texture
   //to the edge of our shape.
   glTexParameterf( GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_REPEAT );
   glTexParameterf( GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_REPEAT );

   //Generate the texture with mipmaps
   gluBuild2DMipmaps( GL_TEXTURE_2D, 3, width, height, GL_RGB, GL_UNSIGNED_BYTE, data );
   free( data ); //free the texture
   return texture; //return whether it was successfull
}

void FreeTexture( GLuint texture )
{
glDeleteTextures( 1, &texture );
}

void cube (void) {
   glBindTexture( GL_TEXTURE_2D, texture ); //bind the texture
   glRotatef( angle, 1.0f, 1.0f, 1.0f );
   glutSolidCube(2);
}

void display (void) {
   glClearColor (0.0,0.0,0.0,1.0);
    glClear (GL_COLOR_BUFFER_BIT);
    glLoadIdentity();
   gluLookAt (0.0, 0.0, 5.0, 0.0, 0.0, 0.0, 0.0, 1.0, 0.0);
   texture = LoadTexture( "texture.raw", 256, 256 ); //load the texture
   glEnable( GL_TEXTURE_2D ); //enable 2D texturing
   glEnable(GL_TEXTURE_GEN_S); //enable texture coordinate generation
   glEnable(GL_TEXTURE_GEN_T);
   cube();
   FreeTexture( texture );
   glutSwapBuffers();
   angle ++;
}

void reshape (int w, int h) {
   glViewport (0, 0, (GLsizei)w, (GLsizei)h);
   glMatrixMode (GL_PROJECTION);
   glLoadIdentity ();
   gluPerspective (60, (GLfloat)w / (GLfloat)h, 1.0, 100.0);
   glMatrixMode (GL_MODELVIEW);
}

int main (int argc, char **argv) {
    glutInit (&argc, argv);
   glutInitDisplayMode (GLUT_DOUBLE);
   glutInitWindowSize (500, 500);
   glutInitWindowPosition (100, 100);
    glutCreateWindow ("A basic OpenGL Window");
    glutDisplayFunc (display);
   glutIdleFunc (display);
   glutReshapeFunc (reshape);
    glutMainLoop ();
    return 0;
}

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