| This sample demonstrates how
to perform shadow mapping under OpenGL.
The shadow mapping technique basically uses
a depth texture or "shadow map" to figure
out whether or not a pixel’s Z value places
it within a shadowed region or not.
This
involves two render passes. The first pass
uses a p-buffer to create a depth texture
from the light’s point of view. On the second
pass, we render our 3D content and perform
a depth comparison between each pixel generated
and the depth texture. If the pixel has
a greater Z value than the depth texture,
the pixel is further away from the light’s
position and we know it lies within a shadowed
region. On the other had, if the pixel’s
Z value is less than the depth texture,
we know that the current pixel is closer
to the light than the object or shadow caster
used to create the depth texture and couldn’t
possible be in a shadowed region.
Note: This sample
uses some nVIDIA specific features and may
not run properly on ATI cards.
Relevant Keywords: wglGetProcAddress,
wglGetExtensionsStringARB, wglCreatePbufferARB,
wglGetPbufferDCARB, wglReleasePbufferDCARB,
wglDestroyPbufferARB, wglChoosePixelFormatARB,
wglBindTexImageARB, wglReleaseTexImageARB,
glPolygonOffset, WGL_SUPPORT_OPENGL_ARB,
WGL_DRAW_TO_PBUFFER_ARB, WGL_BIND_TO_TEXTURE_RGBA_ARB,
WGL_DOUBLE_BUFFER_ARB, WGL_DEPTH_TEXTURE_FORMAT_NV,
WGL_TEXTURE_DEPTH_COMPONENT_NV, WGL_TEXTURE_FORMAT_ARB,
WGL_TEXTURE_RGBA_ARB, WGL_TEXTURE_TARGET_ARB,
WGL_TEXTURE_2D_ARB, GL_TEXTURE_COMPARE_OPERATOR_SGIX,
GL_TEXTURE_LEQUAL_R_SGIX, GL_TEXTURE_COMPARE_SGIX,
GL_CLAMP_TO_EDGE, GL_POLYGON_OFFSET_FILL,
GL_TEXTURE_GEN_MODE, GL_EYE_LINEAR, GL_EYE_PLANE,
GL_TEXTURE_GEN_S, GL_TEXTURE_GEN_T, GL_TEXTURE_GEN_R,
GL_TEXTURE_GEN_Q, GL_S, GL_R, GL_T, and
GL_Q.
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