3D Texture Example Program

/*
 * tex3d - simple 3D texturing program
 *
 * Shows a 3D texture by drawing slices through it.
 */
/* compile: cc -o tex3d tex3d.c -lGL -lX11 */

#include <GL/glx.h>
#include <GL/glu.h>
#include <X11/keysym.h>
#include <stdlib.h>
#include <stdio.h>

static int attributeList[] = { GLX_RGBA, None };

unsigned int tex[64][64][64];

/* generate a simple 3D texture */
static void
make_texture(void) {
    int i, j, k;
    unsigned int *p = &tex[0][0][0];

    for (i=0; i<64; i++) {
        for (j=0; j<64; j++) {
            for (k=0; k<64; k++) {
                if (i < 10 || i > 48 ||
                    j < 10 || j > 48 ||
                    k < 10 || k > 48) {
                    if (i < 2 || i > 62 ||
                        j < 2 || j > 62 ||
                        k < 2 || k > 62) {
                        *p++ = 0x00000000;
                    } else {
                        *p++ = 0xff80ffff;
                    }
                } else {
                    *p++ = 0x000000ff;
                }
            }
        }
    }
}

static void
init(void) {
    make_texture();
    glEnable(GL_TEXTURE_3D_EXT);
    glEnable(GL_BLEND);
    glBlendFunc(GL_SRC_ALPHA, GL_ONE);
    glClearColor(0.2,0.2,0.5,1.0);
    glPixelStorei(GL_UNPACK_ALIGNMENT, 1);

    glMatrixMode(GL_PROJECTION);
    gluPerspective(60.0, 1.0, 1.0, 100.0 );
    glMatrixMode(GL_MODELVIEW);
    glTranslatef(0.,0.,-3.0);
    glMatrixMode(GL_TEXTURE);


    /* Similar to defining a 2D texture, but note the setting of the */
    /* wrap parameter for the R coordinate.  Also, for 3D textures   */
    /* you probably won't need mipmaps, hence the linear min filter. */
    glTexEnvf(GL_TEXTURE_ENV, GL_TEXTURE_ENV_MODE, GL_MODULATE);
    glTexParameteri(GL_TEXTURE_3D_EXT, GL_TEXTURE_MIN_FILTER, 
                                                         GL_LINEAR);
    glTexParameteri(GL_TEXTURE_3D_EXT, GL_TEXTURE_WRAP_S, GL_CLAMP);
    glTexParameteri(GL_TEXTURE_3D_EXT, GL_TEXTURE_WRAP_T, GL_CLAMP);
    glTexParameteri(GL_TEXTURE_3D_EXT, GL_TEXTURE_WRAP_R_EXT, 
                                                          GL_CLAMP);
    glTexImage3DEXT(GL_TEXTURE_3D_EXT, 0, 4, 64, 64, 64, 0,
                    GL_RGBA, GL_UNSIGNED_BYTE, tex);
}

#define NUMSLICES 256

static void
draw_scene(void) {
    int i;
    float r, dr, z, dz;
    
    glColor4f(1, 1, 1, 1.4/NUMSLICES);
    glClear(GL_COLOR_BUFFER_BIT);

    /* Display the entire 3D texture by drawing a series of quads */
    /* that  slice through the texture coordinate space.  Note that */
    /* the transformations below are applied to the texture matrix, */
    /* not the modelview matrix. */
       
    glLoadIdentity();
    /* center the texture coords around the [0,1] cube */
    glTranslatef(.5,.5,.5);
    /* a rotation just to make the picture more interesting */
    glRotatef(45.,1.,1.,.5);

    /* to make sure that the texture coords, after arbitrary */
    /* rotations, still fully contain the [0,1] cube, make them span */
    /* a range sqrt(3)=1.74 wide */
    r = -0.87; dr = 1.74/NUMSLICES;
    z = -1.00; dz = 2.00/NUMSLICES;
    for (i=0; i < NUMSLICES; i++) {
        glBegin(GL_TRIANGLE_STRIP);
        glTexCoord3f(-.87,-.87,r); glVertex3f(-1,-1,z); 
        glTexCoord3f(-.87, .87,r); glVertex3f(-1, 1,z); 
        glTexCoord3f( .87,-.87,r); glVertex3f( 1,-1,z); 
        glTexCoord3f( .87, .87,r); glVertex3f( 1, 1,z); 
        glEnd();
        r += dr;
        z += dz;
    }
}

/* process input and error functions and main(), which handles window  
 * setup, go here. 
 */