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    glViewport(0, 0, winWidth, winHeight);
  75
  76    glDisable(GL_STENCIL_TEST);
  77    glDisable(GL_DEPTH_TEST);
  78    glRasterPos2f(0, 0);
  79
  80    glDrawPixels(winWidth, winHeight, GL_LUMINANCE, GL_FLOAT, depthValues);
  81
  82    glPopMatrix();
  83    glMatrixMode(GL_PROJECTION);
  84    glPopMatrix();
  85    free(depthValues);
  86
  87    glPopAttrib();
  88 }
  89
  90
  91
  92
  93 /*
  94  * Copy the alpha channel values into the current color buffer as a
  95  * grayscale image.
  96  * Input:  winWidth, winHeight - size of the window
  97  */
  98 void
  99 ShowAlphaBuffer( GLsizei winWidth, GLsizei winHeight )
 100 {
 101    GLubyte *alphaValues;
 102
 103    glPixelStorei(GL_UNPACK_ALIGNMENT, 1);
 104    glPixelStorei(GL_PACK_ALIGNMENT, 1);
 105
 106    /* Read alpha values */
 107    alphaValues = (GLubyte *) malloc(winWidth * winHeight * sizeof(GLubyte));
 108    assert(alphaValues);
 109    glReadPixels(0, 0, winWidth, winHeight, GL_ALPHA, GL_UNSIGNED_BYTE, alphaValues);
 110
 111    /* save GL state */
 112    glPushAttrib(GL_CURRENT_BIT | GL_DEPTH_BUFFER_BIT | GL_STENCIL |
 113                 GL_TRANSFORM_BIT | GL_VIEWPORT_BIT);
 114
 115    /* setup raster pos for glDrawPixels */
 116    glMatrixMode(GL_PROJECTION);
 117    glPushMatrix();
 118    glLoadIdentity();
 119
 120    glOrtho(0.0, (GLdouble) winWidth, 0.0, (GLdouble) winHeight, -1.0, 1.0);
 121    glMatrixMode(GL_MODELVIEW);
 122    glPushMatrix();
 123    glLoadIdentity();
 124
 125    glViewport(0, 0, winWidth, winHeight);
 126
 127    glDisable(GL_STENCIL_TEST);
 128    glDisable(GL_DEPTH_TEST);
 129    glRasterPos2f(0, 0);
 130
 131    glDrawPixels(winWidth, winHeight, GL_LUMINANCE, GL_UNSIGNED_BYTE, alphaValues);
 132
 133    glPopMatrix();
 134    glMatrixMode(GL_PROJECTION);
 135    glPopMatrix();
 136    free(alphaValues);
 137
 138    glPopAttrib();
 139 }
 140
 141
 142
 143 /*
 144  * Copy the stencil buffer values into the current color buffer as a
 145  * grayscale image.
 146  * Input:  winWidth, winHeight - size of the window
 147  *         scale, bias - scale and bias to apply to stencil values for display
 148  */
 149 void
 150 ShowStencilBuffer( GLsizei winWidth, GLsizei winHeight,
 151                    GLfloat scale, GLfloat bias )
 152 {
 153    GLubyte *stencilValues;
 154
 155    glPixelStorei(GL_UNPACK_ALIGNMENT, 1);
 156    glPixelStorei(GL_PACK_ALIGNMENT, 1);
 157
 158    /* Read stencil values */
 159    stencilValues = (GLubyte *) malloc(winWidth * winHeight * sizeof(GLubyte));
 160    assert(stencilValues);
 161    glReadPixels(0, 0, winWidth, winHeight, GL_STENCIL_INDEX, GL_UNSIGNED_BYTE, stencilValues);
 162
 163    /* save GL state */
 164    glPushAttrib(GL_CURRENT_BIT | GL_DEPTH_BUFFER_BIT | GL_STENCIL_BUFFER_BIT |
 165                 GL_PIXEL_MODE_BIT | GL_TRANSFORM_BIT | GL_VIEWPORT_BIT);
 166
 167    /* setup raster pos for glDrawPixels */
 168    glMatrixMode(GL_PROJECTION);
 169    glPushMatrix();
 170    glLoadIdentity();
 171
 172    glOrtho(0.0, (GLdouble) winWidth, 0.0, (GLdouble) winHeight, -1.0, 1.0);
 173    glMatrixMode(GL_MODELVIEW);
 174    glPushMatrix();
 175    glLoadIdentity();
 176
 177    glViewport(0, 0, winWidth, winHeight);
 178
 179    glDisable(GL_STENCIL_TEST);
 180    glDisable(GL_DEPTH_TEST);
 181    glRasterPos2f(0, 0);
 182
 183    glPixelTransferf(GL_RED_SCALE, scale);
 184    glPixelTransferf(GL_RED_BIAS, bias);
 185    glPixelTransferf(GL_GREEN_SCALE, scale);
 186    glPixelTransferf(GL_GREEN_BIAS, bias);
 187    glPixelTransferf(GL_BLUE_SCALE, scale);
 188    glPixelTransferf(GL_BLUE_BIAS, bias);
 189
 190    glDrawPixels(winWidth, winHeight, GL_LUMINANCE, GL_UNSIGNED_BYTE, stencilValues);
 191
 192    glPopMatrix();
 193    glMatrixMode(GL_PROJECTION);
 194    glPopMatrix();
 195    free(stencilValues);
 196
 197    glPopAttrib();
 198 }