/* Demo of using binding to allow the efficient use of multiple textures.
   6 textures are loaded and bound to the sides of a cube.

   Scott D. Anderson
   Fall 2002 original
   Fall 2003 adapted to use TW
*/

#include <stdlib.h>
#include <stdio.h>
#include <tw.h>

/* ================================================================
   Cube
*/

GLfloat vertices[][3] = { {-1,-1,-1}, {+1,-1,-1}, {+1,+1,-1}, {-1,+1,-1},
                          {-1,-1,+1}, {+1,-1,+1}, {+1,+1,+1}, {-1,+1,+1}};

GLuint textureIDs[6];

/* Polgons as faces of a cube.  We set the color and texture for each
   vertex. Vertex a is the upper left (that is, it corresponds to the
   upper left of the texture, and then we go counterclockwise, so vertex b
   is the lower left of the texture.  */

void polygon(int a, int b, int c , int d) {
    /* draw a polygon via list of vertices */
    glBegin(GL_POLYGON);
    glTexCoord2f(0,0);
    glVertex3fv(vertices[a]);
    glTexCoord2f(0,1);
    glVertex3fv(vertices[b]);
    glTexCoord2f(1,1);
    glVertex3fv(vertices[c]);
    glTexCoord2f(1,0);
    glVertex3fv(vertices[d]);
    glEnd();
}

void texturecube() {
    /* map vertices to faces */
    glBindTexture(GL_TEXTURE_2D, textureIDs[0]);
    polygon(0,3,2,1);                // back: z=-1
    glBindTexture(GL_TEXTURE_2D, textureIDs[1]);
    polygon(6,2,3,7);                // top: y=+1
    glBindTexture(GL_TEXTURE_2D, textureIDs[2]);
    polygon(0,4,7,3);                // left: x=-1
    glBindTexture(GL_TEXTURE_2D, textureIDs[3]);
    polygon(6,5,1,2);                // right: x=+1
    glBindTexture(GL_TEXTURE_2D, textureIDs[4]);
    polygon(6,7,4,5);                // front: z=+1
    glBindTexture(GL_TEXTURE_2D, textureIDs[5]);
    polygon(0,1,5,4);                // bottom: y=-1
}

void init() {
    glGenTextures(6,textureIDs); /* get all the texture ids */
    
    twLoadTexture(textureIDs[0],"mandrill.ppm");
    twLoadTexture(textureIDs[1],"cokecan.ppm");
    twLoadTexture(textureIDs[2],"homer2.ppm");
    twLoadTexture(textureIDs[3],"peterms.ppm");
    twLoadTexture(textureIDs[4],"eac512x256.ppm");
    twLoadTexture(textureIDs[5],"USflag.ppm");
    // for(int i=0; i<6; i++) { printf("%d: %d\n",i,textureIDs[i]); }
}    

void display(void) {
    twDisplayInit();
    twCamera();
    glPushAttrib(GL_ALL_ATTRIB_BITS);

    glEnable(GL_TEXTURE_2D);        // From now on, we'll use textures
    glColor3f(1,1,1);                // on white cubes

    texturecube();

    glPopAttrib();
    glFlush();
    glutSwapBuffers();
}

int main(int  argc, char *argv[]) {
    glutInit(&argc, argv);
    glutInitDisplayMode(GLUT_RGB | GLUT_DOUBLE | GLUT_DEPTH);
    glutInitWindowSize(500,500);
    glutCreateWindow(argv[0]);
    init();
    glutDisplayFunc(display);
    twBoundingBox(-2,2,-2,2,-1,1);
    twMainInit();
    glutMainLoop();
    return (0);
}