I wonder what is the range of shininess in COLLADA document?
I'm a bit confused about why there is no certain value in the spec on that..
Thanks in advance.
I tried to get an answer from the guy who currently does most of the work on the Collada material system, but I never heard back from him. I think the range of shininess isn't currently specified in Collada. OpenGL's max shininess is 128 IIRC, so [0, 128] might be a good range to use.
The lighting model equations for the common shaders (e.g <phong> and <blinn>) have been under discussion in the work group and the issue is being tracked in the Khronos Bugzilla.
I can confirm that prior to COLLADA 1.4 the value was a GL style exponent as Steven said. With the introduction of effects and GLES and GLSL profiles, there has been some movement away from them for the <profile_common> shaders.
Yes there appear to be misunderstanding of blinn between the realtime 3D guys and the DCC guys.
DCC assumed Blinn-Torrance-Sparrow
while RT guys assumed Blinn-Phong.
FXComposer2 attempts to compensate for this by detecting the usage pattern and switching to the appropriate function.
If shininess 0 to 1 do Blinn-Torrance-Sparrow
else if shininess >1 do Blinn-Phong
Blinn-Phong is the typical phong equations using the half vector.
Blinn-Torrance-Sparrow is quite a bit more complicated.
I'd suggest installing FXComposer2 and using the effects wizard to generate a Blinn CgFX file then utilizing that code as the Blinn-Torrance-Sparrow portion of your shader.