Shrimp Shader Generator FLTK2 GUI (SVN)

Small typo, forgot the & special character.

Modified the diffuse block to add the option to use Pixie's diffuse() in its 2nd form, with 3 arguments (surface point, normal, and angle).

Update to filterstep() and spline() shadeops, added extra filters supported by Pixie: blackman-harris, mitchell, sinc.

Added __nondiffuse and __nonspecular to light shaders, local illumination models proceed according to return status from lightsource() and these variable's content. Fixed cracked glazed clay example and point initialization in Voronoi blocks.

Added some fixes and tweaks to shading models headers, and extras.

Added the Buratti and Lommel-Seeliger blocks as well as their respective functions in the shading models header. Added some useful constants in helpers. Tweaked the shading models and distributions in their respective headers, into hopefully a more readable code. Added a note on the Cook-Torrance block regarding normalization of the Trowbridge-Reitz microfacet distribution.

FIX: unsupported display could be assigned when changing render engine from the main window

SConstruct file cleanup

ENH: texture basic commands are loaded from renderers file

Updated texture blocks for the blur/width problem - these values were always bypassed by sblur/tblur and swidth/twidth. Added usage information, and an extra option for 3delight, for the texture() shadeop, the ability to specify the samples to use when the filter type is box.