progs/tests/stencilreaddraw.c

   1 /*
   2  * Test glRead/DrawPixels for GL_STENCIL_INDEX, with pixelzoom.
   3  *
   4  * Brian Paul
   5  * 8 April 2010
   6  */
   7
   8 #include <assert.h>
   9 #include <stdio.h>
  10 #include <stdlib.h>
  11 #include <math.h>
  12 #include <GL/glew.h>
  13 #include <GL/glut.h>
  14
  15 static GLint WinWidth = 500, WinHeight = 500;
  16 static GLboolean TestPacking = GL_FALSE;
  17 static GLboolean TestList = GL_FALSE;
  18
  19
  20 static GLuint StencilValue = 192;
  21
  22 static void Display(void)
  23 {
  24    GLubyte stencil[100 * 100 * 2];
  25    GLubyte stencil2[400 * 400]; /* *2 to test pixelstore stuff */
  26    GLuint list;
  27
  28    glClearColor(0.5, 0.5, 0.5, 1.0);
  29    glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT | GL_STENCIL_BUFFER_BIT);
  30
  31    glEnable(GL_DEPTH_TEST);
  32
  33    glStencilOp(GL_INVERT, GL_KEEP, GL_REPLACE);
  34    glStencilFunc(GL_ALWAYS, StencilValue, ~0);
  35    glEnable(GL_STENCIL_TEST);
  36
  37    /* draw a sphere */
  38    glViewport(0, 0, 100, 100);
  39    glMatrixMode(GL_PROJECTION);
  40    glLoadIdentity();
  41    glOrtho(-1, 1, -1, 1, -1, 0);  /* clip away back half of sphere */
  42    glMatrixMode(GL_MODELVIEW);
  43    glLoadIdentity();
  44    glutSolidSphere(1.0, 20, 10);
  45
  46    glDisable(GL_STENCIL_TEST);
  47
  48    if (TestPacking) {
  49       glPixelStorei(GL_PACK_ROW_LENGTH, 120);
  50       glPixelStorei(GL_PACK_SKIP_PIXELS, 5);
  51    }
  52
  53    /* read the stencil image */
  54    glReadPixels(0, 0, 100, 100, GL_STENCIL_INDEX, GL_UNSIGNED_BYTE, stencil);
  55    {
  56       GLubyte min, max;
  57       int i;
  58       min = max = stencil[0];
  59       for (i = 1; i < 100 * 100; i++) {
  60          if (stencil[i] < min)
  61             min = stencil[i];
  62          if (stencil[i] > max)
  63             max = stencil[i];
  64       }
  65       printf("Stencil value range: [%u, %u]\n", min, max);
  66       if (max != StencilValue) {
  67          printf("Error: expected max stencil val of %u, found %u\n",
  68                 StencilValue, max);
  69       }
  70    }
  71
  72    /* Draw the Z image as luminance above original rendering */
  73    glWindowPos2i(0, 100);
  74    glDrawPixels(100, 100, GL_LUMINANCE, GL_UNSIGNED_BYTE, stencil);
  75
  76    if (1) {
  77       if (TestPacking) {
  78          glPixelStorei(GL_PACK_ROW_LENGTH, 0);
  79          glPixelStorei(GL_PACK_SKIP_PIXELS, 0);
  80          glPixelStorei(GL_UNPACK_ROW_LENGTH, 120);
  81          glPixelStorei(GL_UNPACK_SKIP_PIXELS, 5);
  82       }
  83
  84       /* draw stencil image with scaling (into stencil buffer) */
  85       glPixelZoom(4.0, 4.0);
  86       glColor4f(1, 0, 0, 0);
  87       glWindowPos2i(100, 0);
  88
  89       if (TestList) {
  90          list = glGenLists(1);
  91          glNewList(list, GL_COMPILE);
  92          glDrawPixels(100, 100, GL_STENCIL_INDEX, GL_UNSIGNED_BYTE, stencil);
  93          glEndList();
  94          glCallList(list);
  95          glDeleteLists(list, 1);
  96       }
  97       else {
  98          glDrawPixels(100, 100, GL_STENCIL_INDEX, GL_UNSIGNED_BYTE, stencil);
  99       }
 100
 101       if (TestPacking) {
 102          glPixelStorei(GL_UNPACK_ROW_LENGTH, 0);
 103          glPixelStorei(GL_UNPACK_SKIP_PIXELS, 0);
 104       }
 105
 106       /* read back scaled stencil image */
 107       glReadPixels(100, 0, 400, 400, GL_STENCIL_INDEX,
 108                    GL_UNSIGNED_BYTE, stencil2);
 109       /* draw as luminance */
 110       glPixelZoom(1.0, 1.0);
 111       glWindowPos2i(100, 0);
 112       glDrawPixels(400, 400, GL_LUMINANCE, GL_UNSIGNED_BYTE, stencil2);
 113    }
 114
 115    glutSwapBuffers();
 116 }
 117
 118
 119 static void Reshape(int width, int height)
 120 {
 121    WinWidth = width;
 122    WinHeight = height;
 123    glViewport(0, 0, width, height);
 124 }
 125
 126
 127 static void Key(unsigned char key, int x, int y)
 128 {
 129    (void) x;
 130    (void) y;
 131    switch (key) {
 132       case 'p':
 133          TestPacking = !TestPacking;
 134          printf("Test pixel pack/unpack: %d\n", TestPacking);
 135          break;
 136       case 'l':
 137          TestList = !TestList;
 138          printf("Test dlist: %d\n", TestList);
 139          break;
 140       case 27:
 141          exit(0);
 142          break;
 143    }
 144    glutPostRedisplay();
 145 }
 146
 147
 148 static void Init(void)
 149 {
 150    const GLfloat blue[4] = {.1, .1, 1.0, 1.0};
 151    const GLfloat gray[4] = {0.2, 0.2, 0.2, 1.0};
 152    const GLfloat white[4] = {1.0, 1.0, 1.0, 1.0};
 153    const GLfloat pos[4] = {0, 0, 10, 0};
 154    GLint bits;
 155
 156    printf("GL_VERSION = %s\n", (char *) glGetString(GL_VERSION));
 157    printf("GL_RENDERER = %s\n", (char *) glGetString(GL_RENDERER));
 158
 159    glGetIntegerv(GL_STENCIL_BITS, &bits);
 160    printf("Stencil bits: %d\n", bits);
 161
 162    assert(bits >= 8);
 163
 164    glMaterialfv(GL_FRONT_AND_BACK, GL_DIFFUSE, blue);
 165    glLightfv(GL_LIGHT0, GL_AMBIENT, gray);
 166    glLightfv(GL_LIGHT0, GL_DIFFUSE, white);
 167    glLightfv(GL_LIGHT0, GL_POSITION, pos);
 168    glEnable(GL_LIGHTING);
 169    glEnable(GL_LIGHT0);
 170 }
 171
 172
 173 int main(int argc, char *argv[])
 174 {
 175    glutInit(&argc, argv);
 176    glutInitWindowPosition(0, 0);
 177    glutInitWindowSize(WinWidth, WinHeight);
 178    glutInitDisplayMode(GLUT_RGB | GLUT_DEPTH | GLUT_STENCIL | GLUT_DOUBLE);
 179    glutCreateWindow(argv[0]);
 180    glewInit();
 181    glutReshapeFunc(Reshape);
 182    glutKeyboardFunc(Key);
 183    glutDisplayFunc(Display);
 184    Init();
 185    glutMainLoop();
 186    return 0;
 187 }