diff options
Diffstat (limited to 'progs/demos/showbuffer.c')
| -rw-r--r-- | progs/demos/showbuffer.c | 198 |
1 files changed, 198 insertions, 0 deletions
diff --git a/progs/demos/showbuffer.c b/progs/demos/showbuffer.c new file mode 100644 index 0000000000..b0cedea217 --- /dev/null +++ b/progs/demos/showbuffer.c @@ -0,0 +1,198 @@ +/* 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(); +} |