2D Texture Class

This class wraps a great deal, but not all, of the GL texture interface needed for typical 2D texture use. I've tried to simplify the handling of texture objects without masking any of their capability; hence the qualifier 'a great deal'. Familiarity with the OpenGL texturing API is required; like most of the library, code comments are rare, and this document will not attempt to explain basic GL texture operation. If you know how to use the texturing API you may find this class useful; if you don't, this class isn't going to help you. The public interface is presented below. In a nutshell, instantiate a CgleTexture object, either dynamically or statically. Set the desired filter modes, wrap mode, etc, then call one of the 'build' functions. A GL texture handle will be acquired, the image (and optional mipmaps) created, and GL texture object state will be configured with the filter mode, wrap mode, etc, you'd selected. Also refer to the demo programs available at http://www.brightideassoftware.com/gle32v4home.aspx for examples of the use of this class.

Features include automatic mipmap generation, ability to load images in a variety of formats from either embedded resources or external files, and use of the GL_ARB_texture_compression extension to perform runtime compression of textures, then optionally store the compressed version for later use on the client machine. Subsequent executions of the texture code will attempt to load the compressed file (saving compression time); failure to succesfully load the compressed file will result in it's regeneration, ensuring smooth operation of the client app. Images are optionally automatically resized to the next lower 2^n dimension if they aren't already valid 2^n values.

A note about loading embedded resources: The CgleTextgure class will load images stored as a resource in a variety of formats (.bmp, .jpg, .ppm, .pgm, most standard .tga formats). In order to store/reload images in formats other than .bmp (which are listed in an .rc file under the standard heading 'Bitmap'), they must be labeled as an 'IMAGE' resource. This is hard-coded into the class, although obviously you can change it to something else if you like. A typical entry in an .rc file should look something like this: IDI_ROCKWALL_IMAGE      IMAGE    "resources\\relief_rockwall.jpg". Note the 'IMAGE' tag, second item in the line. This, combined with the resource identifier (IDI_ROCKWALL_IMAGE in this case), is what CgleTexture looks for when it loads an embedded image.

The code for converting a height map to a normal map has it's roots in a white paper by Mark Kilgard; some of the procedural texture code has it's roots in Linas Vepstas' original GLE library.