progs/util/showbuffer.c

   1 /* showbuffer.c */
   2
   3
   4 /*
   5  * Copy the depth buffer to the color buffer as a grayscale image.
   6  * Useful for inspecting the depth buffer values.
   7  *
   8  * This program is in the public domain.
   9  *
  10  * Brian Paul   November 4, 1998
  11  */
  12
  13
  14 #include <assert.h>
  15 #include <stdlib.h>
  16 #include <GL/gl.h>
  17 #include "showbuffer.h"
  18
  19
  20
  21 /*
  22  * Copy the depth buffer values into the current color buffer as a
  23  * grayscale image.
  24  * Input:  winWidth, winHeight - size of the window
  25  *         zBlack - the Z value which should map to black (usually 1)
  26  *         zWhite - the Z value which should map to white (usually 0)
  27  */
  28 void
  29 ShowDepthBuffer( GLsizei winWidth, GLsizei winHeight,
  30                  GLfloat zBlack, GLfloat zWhite )
  31 {
  32    GLfloat *depthValues;
  33
  34    assert(zBlack >= 0.0);
  35    assert(zBlack <= 1.0);
  36    assert(zWhite >= 0.0);
  37    assert(zWhite <= 1.0);
  38    assert(zBlack != zWhite);
  39
  40    glPixelStorei(GL_UNPACK_ALIGNMENT, 1);
  41    glPixelStorei(GL_PACK_ALIGNMENT, 1);
  42
  43    /* Read depth values */
  44    depthValues = (GLfloat *) malloc(winWidth * winHeight * sizeof(GLfloat));
  45    assert(depthValues);
  46    glReadPixels(0, 0, winWidth, winHeight, GL_DEPTH_COMPONENT,
  47                 GL_FLOAT, depthValues);
  48
  49    /* Map Z values from [zBlack, zWhite] to gray levels in [0, 1] */
  50    /* Not using glPixelTransfer() because it's broke on some systems! */
  51    if (zBlack != 0.0 || zWhite != 1.0) {
  52       GLfloat scale = 1.0 / (zWhite - zBlack);
  53       GLfloat bias = -zBlack * scale;
  54       int n = winWidth * winHeight;
  55       int i;
  56       for (i = 0; i < n; i++)
  57          depthValues[i] = depthValues[i] * scale + bias;
  58    }
  59
  60    /* save GL state */
  61    glPushAttrib(GL_CURRENT_BIT | GL_DEPTH_BUFFER_BIT | GL_STENCIL_BUFFER_BIT |
  62                 GL_TRANSFORM_BIT | GL_VIEWPORT_BIT);
  63
  64    /* setup raster pos for glDrawPixels */
  65    glMatrixMode(GL_PROJECTION);
  66    glPushMatrix();
  67    glLoadIdentity();
  68
  69    glOrtho(0.0, (GLdouble) winWidth, 0.0, (GLdouble) winHeight, -1.0, 1.0);
  70    glMatrixMode(GL_MODELVIEW);
  71    glPushMatrix();
  72    glLoadIdentity();
  73
  74    glDisable(GL_STENCIL_TEST);
  75    glDisable(GL_DEPTH_TEST);
  76    glRasterPos2f(0, 0);
  77
  78    glDrawPixels(winWidth, winHeight, GL_LUMINANCE, GL_FLOAT, depthValues);
  79
  80    glPopMatrix();
  81    glMatrixMode(GL_PROJECTION);
  82    glPopMatrix();
  83    free(depthValues);
  84
  85    glPopAttrib();
  86 }
  87
  88
  89
  90
  91 /*
  92  * Copy the alpha channel values into the current color buffer as a
  93  * grayscale image.
  94  * Input:  winWidth, winHeight - size of the window
  95  */
  96 void
  97 ShowAlphaBuffer( GLsizei winWidth, GLsizei winHeight )
  98 {
  99    GLubyte *alphaValues;
 100
 101    glPixelStorei(GL_UNPACK_ALIGNMENT, 1);
 102    glPixelStorei(GL_PACK_ALIGNMENT, 1);
 103
 104    /* Read alpha values */
 105    alphaValues = (GLubyte *) malloc(winWidth * winHeight * sizeof(GLubyte));
 106    assert(alphaValues);
 107    glReadPixels(0, 0, winWidth, winHeight, GL_ALPHA, GL_UNSIGNED_BYTE, alphaValues);
 108
 109    /* save GL state */
 110    glPushAttrib(GL_CURRENT_BIT | GL_DEPTH_BUFFER_BIT | GL_STENCIL |
 111                 GL_TRANSFORM_BIT | GL_VIEWPORT_BIT);
 112
 113    /* setup raster pos for glDrawPixels */
 114    glMatrixMode(GL_PROJECTION);
 115    glPushMatrix();
 116    glLoadIdentity();
 117
 118    glOrtho(0.0, (GLdouble) winWidth, 0.0, (GLdouble) winHeight, -1.0, 1.0);
 119    glMatrixMode(GL_MODELVIEW);
 120    glPushMatrix();
 121    glLoadIdentity();
 122
 123    glDisable(GL_STENCIL_TEST);
 124    glDisable(GL_DEPTH_TEST);
 125    glRasterPos2f(0, 0);
 126
 127    glDrawPixels(winWidth, winHeight, GL_LUMINANCE, GL_UNSIGNED_BYTE, alphaValues);
 128
 129    glPopMatrix();
 130    glMatrixMode(GL_PROJECTION);
 131    glPopMatrix();
 132    free(alphaValues);
 133
 134    glPopAttrib();
 135 }
 136
 137
 138
 139 /*
 140  * Copy the stencil buffer values into the current color buffer as a
 141  * grayscale image.
 142  * Input:  winWidth, winHeight - size of the window
 143  *         scale, bias - scale and bias to apply to stencil values for display
 144  */
 145 void
 146 ShowStencilBuffer( GLsizei winWidth, GLsizei winHeight,
 147                    GLfloat scale, GLfloat bias )
 148 {
 149    GLubyte *stencilValues;
 150
 151    glPixelStorei(GL_UNPACK_ALIGNMENT, 1);
 152    glPixelStorei(GL_PACK_ALIGNMENT, 1);
 153
 154    /* Read stencil values */
 155    stencilValues = (GLubyte *) malloc(winWidth * winHeight * sizeof(GLubyte));
 156    assert(stencilValues);
 157    glReadPixels(0, 0, winWidth, winHeight, GL_STENCIL_INDEX, GL_UNSIGNED_BYTE, stencilValues);
 158
 159    /* save GL state */
 160    glPushAttrib(GL_CURRENT_BIT | GL_DEPTH_BUFFER_BIT | GL_STENCIL_BUFFER_BIT |
 161                 GL_PIXEL_MODE_BIT | GL_TRANSFORM_BIT | GL_VIEWPORT_BIT);
 162
 163    /* setup raster pos for glDrawPixels */
 164    glMatrixMode(GL_PROJECTION);
 165    glPushMatrix();
 166    glLoadIdentity();
 167
 168    glOrtho(0.0, (GLdouble) winWidth, 0.0, (GLdouble) winHeight, -1.0, 1.0);
 169    glMatrixMode(GL_MODELVIEW);
 170    glPushMatrix();
 171    glLoadIdentity();
 172
 173    glDisable(GL_STENCIL_TEST);
 174    glDisable(GL_DEPTH_TEST);
 175    glRasterPos2f(0, 0);
 176
 177    glPixelTransferf(GL_RED_SCALE, scale);
 178    glPixelTransferf(GL_RED_BIAS, bias);
 179    glPixelTransferf(GL_GREEN_SCALE, scale);
 180    glPixelTransferf(GL_GREEN_BIAS, bias);
 181    glPixelTransferf(GL_BLUE_SCALE, scale);
 182    glPixelTransferf(GL_BLUE_BIAS, bias);
 183
 184    glDrawPixels(winWidth, winHeight, GL_LUMINANCE, GL_UNSIGNED_BYTE, stencilValues);
 185
 186    glPopMatrix();
 187    glMatrixMode(GL_PROJECTION);
 188    glPopMatrix();
 189    free(stencilValues);
 190
 191    glPopAttrib();
 192 }