Image Texturing

also supports an image texture. This texture allows you to use images to modify the characteristics of a surface. You can use three-channel images to modify the any or all of the ambient, diffuse, and specular colors of a surface. If you are using the Utah Raster Toolkit, you can also use single-channel images to modify surface reflectance, transparency, and the specular exponent. You can also use a single-channel image to apply a bump map to a surface.

In all but the bump-mapping case, a component is modified by multiplying the given value by the value computed by the texturing function. When using the Utah Raster Toolkit, surface characteristics are modified in proportion to the value of the alpha channel in the image. If there is no alpha channel, or you are not using the Utah Raster Toolkit, alpha is assumed to be everywhere equal to 1.

$\begin{defkey}{component}{$<${\em Component}$>$} The named component will be modified. \end{defkey}$
Possible surface components are: ambient (modify ambient color), diffuse (modify diffuse color), specular (modify specular color), specpow, (modify specular exponent), reflect, (modify reflectivity), transp (modify transparency), bump, (modify surface normal). The specpow, reflect, transp, and bump components require the use of a single-channel image.

$\begin{defkey}{range}{{\em high low}} Specify the range of values to which the... ...to {\em low}. Intermediate values will be linearly interpolated. \end{defkey}$

$\begin{defkey}{smooth}{} When given, pixel averaging will be performed in orde... ...th the sampled image. If not specified, no averaging will occur. \end{defkey}$

$\begin{defkey}{textsurf}{$<${\em Surface Specification}$>$} For use when modif... ...bject's unmodified default surface characteristics are retained. \end{defkey}$
The usual behavior is for the object's default surface properties to be used.

$\begin{defkey}{tile}{{\em un vn}} Specify how the image should be tiled (repea... ...ro, the image is repeated infinitely along the appropriate axis. \end{defkey}$
Tiling is usually only a concern when planar mapping is being used, though it may also be used if image textures are being scaled. By default un and vn are both zero.

A mapping function may also be associated with an image texture.