|
|
OpenGL (1.2 - 2.0) Code Samples - Page 4
 |
 |
 |
 |
|
Multi-Texture
Blending |
| This sample demonstrates how
to use the OpenGL extensions
ARB_multitexture and
ARB_texture_env_combine in conjunction
with specially encoded vertex colors to
blend three textures together.
This technique is very popular in terrain
rendering engines which use it to blend
dramatically different textures such as
rock and grass together with out creating
a noticeable edge. For example, with three
textures consisting of stone, grass, and
sand you can render a mountain that blends
in patches of grass and sand at its base.
Relevant Keywords: GL_ARB_multitexture,
glActiveTextureARB, glMultiTexCoord2fARB,
glClientActiveTextureARB, glTexEnvi, glVertex3f,
wglGetProcAddress, glGetString, auxDIBImageLoad,
glGenTextures, glBindTexture, glTexParameteri,
glTexImage2D, glEnable, glDisable, glBindTexture,
AUX_RGBImageRec, GL_INTERPOLATE_ARB, GL_SRC_COLOR,
GL_SRC_ALPHA, GL_TEXTURE_ENV, GL_TEXTURE_ENV_MODE,
GL_MODULATE, GL_ADD, GL_TEXTURE0_ARB, GL_TEXTURE1_ARB,
GL_TEXTURE2_ARB, GL_EXTENSIONS, GL_BLEND,
GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_TEXTURE_MAG_FILTER,
GL_LINEAR, GL_UNSIGNED_BYTE, PFNGLACTIVETEXTUREARBPROC,
PFNGLMULTITEXCOORD2FARBPROC, and PFNGLCLIENTACTIVETEXTUREARBPROC.
|
|
 |
 |
 |
 |
|
|
|
|
|
|
|
Color Key
Transparency
|
| This sample demonstrates how
to use a color key to create a RGBA texture
image that supports alpha transparency from
a simpler RGB image like a bitmap (.bmp),
which doesn't support alpha transparency.
Relevant Keywords: auxDIBImageLoad,
glGenTextures, glBindTexture, glTexParameteri,
glTexImage2D, glEnable, glDisable, glBindTexture,
AUX_RGBImageRec, GL_T2F_V3F, GL_RGBA, GL_RGB,
GL_BLEND, GL_DEPTH_TEST, GL_TEXTURE_2D,
GL_TEXTURE_MIN_FILTER, GL_TEXTURE_MAG_FILTER,
GL_NEAREST, and GL_UNSIGNED_BYTE.
|
|
|
|
|
|
|
|
|
|
|
|
|
|
DDS
Texture Loader |
| This sample demonstrates how
to use
ARB_texture_compression to load
.dds compressed texture files. The benefits
of using compressed textures is clearly
shown by loading two identical textures
(512 x 512) for comparison. One is a regular
.bmp texture, and the other is a .dds file
which uses DXT1 compression. With very little
change in image quality, the compressed
texture file not only reduces the file size
down from 768.0 KB to 170.0 KB, but also
includes compressed mip-map levels.
Relevant Keywords: glCompressedTexImage2DARB,
PFNGLCOMPRESSEDTEXIMAGE2DARBPROC, auxDIBImageLoad,
glGenTextures, glBindTexture, glTexParameteri,
glTexImage2D, glEnable, FOURCC_DXT1, FOURCC_DXT3,
FOURCC_DXT5, GL_COMPRESSED_RGBA_S3TC_DXT1_EXT,
GL_COMPRESSED_RGBA_S3TC_DXT3_EXT, GL_COMPRESSED_RGBA_S3TC_DXT5_EXT,
AUX_RGBImageRec, GL_T2F_V3F, GL_TEXTURE_2D,
GL_TEXTURE_MIN_FILTER, GL_TEXTURE_MAG_FILTER,
GL_LINEAR, GL_UNSIGNED_BYTE, and DDSURFACEDESC2.
|
|
|
|
|
|
|
|
|
|
|
|
|
|
Dot3 Per-Pixel
Bump Mapping |
| This sample demonstrates how
to perform Dot3 per-pixel bump mapping using
a normal map and the GL_DOT3_RGB_EXT texture-blending
operation. This technique is sometimes referred
to as per-pixel lighting or per-pixel attenuation,
but Dot3 per-pixel bump-mapping is what
most programmers know it as. Check out the
DirectX9 source
code page for the Direct3D equivalent of
this sample.
This sample also demonstrates how to
create tangent, binormal, and normal vectors,
for each vertex of our test geometry (a
simple cube). These vectors are used during
rendering to define an inverse tangent matrix
for each vertex. This has to be done because
a normal-map stores its normals in tangent-space.
Therefore, we need an inverse tangent matrix
so we can transform our scene's light vector
from object-space into tangent-space. Once
transformed, we then encode this new light
vector as a RGB color and pass it into the
texture blending stage as the vertex's Diffuse
color.
Relevant Keywords: GL_ARB_multitexture,
glActiveTexture, glMultiTexCoord2f, glClientActiveTexture,
glTexEnvi, glVertex3f, wglGetProcAddress,
glGetString, auxDIBImageLoad, glGenTextures,
glBindTexture, glTexParameteri, glTexImage2D,
glEnable, glDisable, glBindTexture, AUX_RGBImageRec,
GL_TEXTURE_ENV, GL_TEXTURE_ENV_MODE, GL_MODULATE,
GL_TEXTURE0, GL_TEXTURE1, GL_EXTENSIONS,
GL_BLEND, GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER,
GL_TEXTURE_MAG_FILTER, GL_LINEAR, GL_UNSIGNED_BYTE,
PFNGLACTIVETEXTUREPROC, PFNGLMULTITEXCOORD2FPROC,
PFNGLCLIENTACTIVETEXTUREPROC, and GL_DOT3_RGB_EXT.
|
|
|
|
|
|
|
|
|
|
|
|
|
|
Alpha Blending in the Frame buffer |
| Demonstrates how to perform
alpha-blending in the frame-buffer. The
sample renders a textured cube which is
alpha-blended into the frame-buffer in such
a way as to create a translucent effect.
Check out the DirectX9
source code page for the Direct3D equivalent
of this sample.
Relevant Keywords: auxDIBImageLoad,
glGenTextures, glBindTexture, glTexParameteri,
glTexImage2D, glEnable, glDisable, glBindTexture,
AUX_RGBImageRec, GL_T2F_V3F, GL_BLEND, GL_DEPTH_TEST,
GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_TEXTURE_MAG_FILTER,
GL_LINEAR, and GL_UNSIGNED_BYTE.
|
|
|
|
|
|
|
|
|
