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/* showbuffer.c */
/*
* Copy the depth buffer to the color buffer as a grayscale image.
* Useful for inspecting the depth buffer values.
*
* This program is in the public domain.
*
* Brian Paul November 4, 1998
*/
#include <assert.h>
#include <stdlib.h>
#include <GL/gl.h>
#include "showbuffer.h"
/*
* Copy the depth buffer values into the current color buffer as a
* grayscale image.
* Input: winWidth, winHeight - size of the window
* zBlack - the Z value which should map to black (usually 1)
* zWhite - the Z value which should map to white (usually 0)
*/
void
ShowDepthBuffer( GLsizei winWidth, GLsizei winHeight,
GLfloat zBlack, GLfloat zWhite )
{
GLfloat *depthValues;
assert(zBlack >= 0.0);
assert(zBlack <= 1.0);
assert(zWhite >= 0.0);
assert(zWhite <= 1.0);
assert(zBlack != zWhite);
glPixelStorei(GL_UNPACK_ALIGNMENT, 1);
glPixelStorei(GL_PACK_ALIGNMENT, 1);
/* Read depth values */
depthValues = (GLfloat *) malloc(winWidth * winHeight * sizeof(GLfloat));
assert(depthValues);
glReadPixels(0, 0, winWidth, winHeight, GL_DEPTH_COMPONENT,
GL_FLOAT, depthValues);
/* Map Z values from [zBlack, zWhite] to gray levels in [0, 1] */
/* Not using glPixelTransfer() because it's broke on some systems! */
if (zBlack != 0.0 || zWhite != 1.0) {
GLfloat scale = 1.0 / (zWhite - zBlack);
GLfloat bias = -zBlack * scale;
int n = winWidth * winHeight;
int i;
for (i = 0; i < n; i++)
depthValues[i] = depthValues[i] * scale + bias;
}
/* save GL state */
glPushAttrib(GL_CURRENT_BIT | GL_DEPTH_BUFFER_BIT | GL_STENCIL_BUFFER_BIT |
GL_TRANSFORM_BIT | GL_VIEWPORT_BIT);
/* setup raster pos for glDrawPixels */
glMatrixMode(GL_PROJECTION);
glPushMatrix();
glLoadIdentity();
glOrtho(0.0, (GLdouble) winWidth, 0.0, (GLdouble) winHeight, -1.0, 1.0);
glMatrixMode(GL_MODELVIEW);
glPushMatrix();
glLoadIdentity();
glViewport(0, 0, winWidth, winHeight);
glDisable(GL_STENCIL_TEST);
glDisable(GL_DEPTH_TEST);
glRasterPos2f(0, 0);
glDrawPixels(winWidth, winHeight, GL_LUMINANCE, GL_FLOAT, depthValues);
glPopMatrix();
glMatrixMode(GL_PROJECTION);
glPopMatrix();
free(depthValues);
glPopAttrib();
}
/*
* Copy the alpha channel values into the current color buffer as a
* grayscale image.
* Input: winWidth, winHeight - size of the window
*/
void
ShowAlphaBuffer( GLsizei winWidth, GLsizei winHeight )
{
GLubyte *alphaValues;
glPixelStorei(GL_UNPACK_ALIGNMENT, 1);
glPixelStorei(GL_PACK_ALIGNMENT, 1);
/* Read alpha values */
alphaValues = (GLubyte *) malloc(winWidth * winHeight * sizeof(GLubyte));
assert(alphaValues);
glReadPixels(0, 0, winWidth, winHeight, GL_ALPHA, GL_UNSIGNED_BYTE, alphaValues);
/* save GL state */
glPushAttrib(GL_CURRENT_BIT | GL_DEPTH_BUFFER_BIT | GL_STENCIL |
GL_TRANSFORM_BIT | GL_VIEWPORT_BIT);
/* setup raster pos for glDrawPixels */
glMatrixMode(GL_PROJECTION);
glPushMatrix();
glLoadIdentity();
glOrtho(0.0, (GLdouble) winWidth, 0.0, (GLdouble) winHeight, -1.0, 1.0);
glMatrixMode(GL_MODELVIEW);
glPushMatrix();
glLoadIdentity();
glViewport(0, 0, winWidth, winHeight);
glDisable(GL_STENCIL_TEST);
glDisable(GL_DEPTH_TEST);
glRasterPos2f(0, 0);
glDrawPixels(winWidth, winHeight, GL_LUMINANCE, GL_UNSIGNED_BYTE, alphaValues);
glPopMatrix();
glMatrixMode(GL_PROJECTION);
glPopMatrix();
free(alphaValues);
glPopAttrib();
}
/*
* Copy the stencil buffer values into the current color buffer as a
* grayscale image.
* Input: winWidth, winHeight - size of the window
* scale, bias - scale and bias to apply to stencil values for display
*/
void
ShowStencilBuffer( GLsizei winWidth, GLsizei winHeight,
GLfloat scale, GLfloat bias )
{
GLubyte *stencilValues;
glPixelStorei(GL_UNPACK_ALIGNMENT, 1);
glPixelStorei(GL_PACK_ALIGNMENT, 1);
/* Read stencil values */
stencilValues = (GLubyte *) malloc(winWidth * winHeight * sizeof(GLubyte));
assert(stencilValues);
glReadPixels(0, 0, winWidth, winHeight, GL_STENCIL_INDEX, GL_UNSIGNED_BYTE, stencilValues);
/* save GL state */
glPushAttrib(GL_CURRENT_BIT | GL_DEPTH_BUFFER_BIT | GL_STENCIL_BUFFER_BIT |
GL_PIXEL_MODE_BIT | GL_TRANSFORM_BIT | GL_VIEWPORT_BIT);
/* setup raster pos for glDrawPixels */
glMatrixMode(GL_PROJECTION);
glPushMatrix();
glLoadIdentity();
glOrtho(0.0, (GLdouble) winWidth, 0.0, (GLdouble) winHeight, -1.0, 1.0);
glMatrixMode(GL_MODELVIEW);
glPushMatrix();
glLoadIdentity();
glViewport(0, 0, winWidth, winHeight);
glDisable(GL_STENCIL_TEST);
glDisable(GL_DEPTH_TEST);
glRasterPos2f(0, 0);
glPixelTransferf(GL_RED_SCALE, scale);
glPixelTransferf(GL_RED_BIAS, bias);
glPixelTransferf(GL_GREEN_SCALE, scale);
glPixelTransferf(GL_GREEN_BIAS, bias);
glPixelTransferf(GL_BLUE_SCALE, scale);
glPixelTransferf(GL_BLUE_BIAS, bias);
glDrawPixels(winWidth, winHeight, GL_LUMINANCE, GL_UNSIGNED_BYTE, stencilValues);
glPopMatrix();
glMatrixMode(GL_PROJECTION);
glPopMatrix();
free(stencilValues);
glPopAttrib();
}
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