Porting Texture Functions

When porting IRIS GL texture functions to OpenGL, keep the following points in mind:

OpenGL doesn't maintain tables of textures; it uses either 1-D texture and 2-D texture only. To reuse the textures from your IRIS GL code, put them in a display list.
OpenGL doesn't automatically generate mipmaps. If you're using mipmaps, you must first call the gluBuild2DMipmaps function.
In OpenGL, you use glEnable and glDisable to turn texturing capabilities on and off.
In OpenGL, texture size is more strictly regulated than in IRIS GL. The size of an OpenGL texture must be:

2n+2b

where n is an integer and b is:
- 0, if the texture has no border
- 1, if the texture has a border pixel (OpenGL textures can have 1-pixel borders.)

The following table lists IRIS GL texture functions and their general OpenGL equivalents.

IRIS GL Function	OpenGL Function	Meaning
textdef2d	glTexImage2D glTexParameter gluBuild2DMipmaps	Specify a 2-D texture image.
textbind	glTexImage2D glTexParameter gluBuild2DMipmaps	Select a texture function.
tevdef	glTexEnv	Define a texture-mapping environment.
tevbind	glTexEnv glTexImage1D	Select a texture environment.
t2	glTexCoord	Set the current texture coordinates.
texgen	glTexGen glGetTexParameter gluBuild1DMipmaps gluBuild2DMipmaps gluScaleImage	Control generation of texture coordinates. Scale an image to an arbitrary size.

For more information on texturing, see the OpenGL Programming Guide.