progs/objviewer/skybox.c

   1
   2
   3 #include <assert.h>
   4 #include <stdio.h>
   5 #include <stddef.h>
   6 #include <stdlib.h>
   7 #include <string.h>
   8 #include <GL/glew.h>
   9 #include <GL/glu.h>
  10 #include "readtex.h"
  11 #include "skybox.h"
  12
  13
  14 static int
  15 load(GLenum target, const char *filename,
  16      GLboolean flipTB, GLboolean flipLR)
  17 {
  18    GLint w, h;
  19    GLenum format;
  20    GLubyte *img = LoadRGBImage( filename, &w, &h, &format );
  21    if (!img) {
  22       printf("Error: couldn't load texture image %s\n", filename);
  23       return 0;
  24    }
  25    assert(format == GL_RGB);
  26
  27    printf("Load cube face 0x%x: %s %d x %d\n", target, filename, w, h);
  28
  29    /* <sigh> the way the texture cube mapping works, we have to flip
  30     * images to make things look right.
  31     */
  32    if (flipTB) {
  33       const int stride = 3 * w;
  34       GLubyte temp[3*1024];
  35       int i;
  36       for (i = 0; i < h / 2; i++) {
  37          memcpy(temp, img + i * stride, stride);
  38          memcpy(img + i * stride, img + (h - i - 1) * stride, stride);
  39          memcpy(img + (h - i - 1) * stride, temp, stride);
  40       }
  41    }
  42    if (flipLR) {
  43       const int stride = 3 * w;
  44       GLubyte temp[3];
  45       GLubyte *row;
  46       int i, j;
  47       for (i = 0; i < h; i++) {
  48          row = img + i * stride;
  49          for (j = 0; j < w / 2; j++) {
  50             int k = w - j - 1;
  51             temp[0] = row[j*3+0];
  52             temp[1] = row[j*3+1];
  53             temp[2] = row[j*3+2];
  54             row[j*3+0] = row[k*3+0];
  55             row[j*3+1] = row[k*3+1];
  56             row[j*3+2] = row[k*3+2];
  57             row[k*3+0] = temp[0];
  58             row[k*3+1] = temp[1];
  59             row[k*3+2] = temp[2];
  60          }
  61       }
  62    }
  63
  64    gluBuild2DMipmaps(target, GL_RGB, w, h, format, GL_UNSIGNED_BYTE, img);
  65    free(img);
  66    return 1;
  67 }
  68
  69
  70 GLuint
  71 LoadSkyBoxCubeTexture(const char *filePosX,
  72                       const char *fileNegX,
  73                       const char *filePosY,
  74                       const char *fileNegY,
  75                       const char *filePosZ,
  76                       const char *fileNegZ)
  77 {
  78    GLuint tex;
  79
  80    glGenTextures(1, &tex);
  81    glBindTexture(GL_TEXTURE_CUBE_MAP, tex);
  82
  83    glTexParameteri(GL_TEXTURE_CUBE_MAP, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
  84    glTexParameteri(GL_TEXTURE_CUBE_MAP, GL_TEXTURE_MIN_FILTER,
  85                    GL_LINEAR_MIPMAP_NEAREST);
  86
  87    if (!load(GL_TEXTURE_CUBE_MAP_POSITIVE_X, filePosX, GL_TRUE, GL_TRUE))
  88       return 0;
  89    if (!load(GL_TEXTURE_CUBE_MAP_NEGATIVE_X, fileNegX, GL_TRUE, GL_TRUE))
  90       return 0;
  91    if (!load(GL_TEXTURE_CUBE_MAP_POSITIVE_Y, filePosY, GL_TRUE, GL_TRUE))
  92       return 0;
  93    if (!load(GL_TEXTURE_CUBE_MAP_NEGATIVE_Y, fileNegY, GL_TRUE, GL_TRUE))
  94       return 0;
  95    if (!load(GL_TEXTURE_CUBE_MAP_POSITIVE_Z, filePosZ, GL_TRUE, GL_TRUE))
  96       return 0;
  97    if (!load(GL_TEXTURE_CUBE_MAP_NEGATIVE_Z, fileNegZ, GL_TRUE, GL_TRUE))
  98       return 0;
  99
 100    return tex;
 101 }
 102
 103
 104 #define eps1 0.99
 105 #define br   20.0  /* box radius */
 106
 107 void
 108 DrawSkyBoxCubeTexture(GLuint tex)
 109 {
 110    struct vertex {
 111       float x, y, z, s, t, r;
 112    };
 113
 114    static const struct vertex verts[24] = {
 115       /* +X side */
 116       { br, -br, -br,  1.0, -eps1, -eps1 },
 117       { br, -br,  br,  1.0, -eps1,  eps1 },
 118       { br,  br,  br,  1.0,  eps1,  eps1 },
 119       { br,  br, -br,  1.0,  eps1, -eps1 },
 120
 121       /* -X side */
 122       { -br,  br, -br,  -1.0,  eps1, -eps1 },
 123       { -br,  br,  br,  -1.0,  eps1,  eps1 },
 124       { -br, -br,  br,  -1.0, -eps1,  eps1 },
 125       { -br, -br, -br,  -1.0, -eps1, -eps1 },
 126
 127       /* +Y side */
 128       {  br,  br, -br,   eps1, 1.0, -eps1 },
 129       {  br,  br,  br,   eps1, 1.0,  eps1 },
 130       { -br,  br,  br,  -eps1, 1.0,  eps1 },
 131       { -br,  br, -br,  -eps1, 1.0, -eps1 },
 132
 133       /* -Y side */
 134       { -br, -br, -br,  -eps1, -1.0, -eps1 },
 135       { -br, -br,  br,  -eps1, -1.0,  eps1 },
 136       {  br, -br,  br,   eps1, -1.0,  eps1 },
 137       {  br, -br, -br,   eps1, -1.0, -eps1 },
 138
 139       /* +Z side */
 140       {  br, -br, br,   eps1, -eps1, 1.0 },
 141       { -br, -br, br,  -eps1, -eps1, 1.0 },
 142       { -br,  br, br,  -eps1,  eps1, 1.0 },
 143       {  br,  br, br,   eps1,  eps1, 1.0 },
 144
 145       /* -Z side */
 146       {  br,  br, -br,   eps1,  eps1, -1.0 },
 147       { -br,  br, -br,  -eps1,  eps1, -1.0 },
 148       { -br, -br, -br,  -eps1, -eps1, -1.0 },
 149       {  br, -br, -br,   eps1, -eps1, -1.0 },
 150    };
 151
 152    static GLuint vbo = 0;
 153
 154    if (!vbo ) {
 155       glGenBuffersARB(1, &vbo);
 156       glBindBufferARB(GL_ARRAY_BUFFER_ARB, vbo);
 157       glBufferDataARB(GL_ARRAY_BUFFER_ARB, sizeof(verts), verts,
 158                       GL_STATIC_DRAW_ARB);
 159    }
 160    else {
 161       glBindBufferARB(GL_ARRAY_BUFFER_ARB, vbo);
 162    }
 163
 164    glTexEnvi(GL_TEXTURE_ENV, GL_TEXTURE_ENV_MODE, GL_REPLACE);
 165
 166    glVertexPointer(3, GL_FLOAT, sizeof(struct vertex),
 167                    (void *) offsetof(struct vertex, x));
 168    glTexCoordPointer(3, GL_FLOAT, sizeof(struct vertex),
 169                      (void *) offsetof(struct vertex, s));
 170    glEnableClientState(GL_VERTEX_ARRAY);
 171    glEnableClientState(GL_TEXTURE_COORD_ARRAY);
 172
 173    glBindTexture(GL_TEXTURE_CUBE_MAP, tex);
 174    glEnable(GL_TEXTURE_CUBE_MAP);
 175
 176    glDisable(GL_BLEND);
 177
 178    glDrawArrays(GL_QUADS, 0, 24);
 179
 180    glDisable(GL_TEXTURE_CUBE_MAP);
 181
 182    glDisableClientState(GL_VERTEX_ARRAY);
 183    glDisableClientState(GL_TEXTURE_COORD_ARRAY);
 184
 185    glBindBufferARB(GL_ARRAY_BUFFER_ARB, 0);
 186 }
 187