Fix for Blender 2.74.5 MultiView. Extended Texture Mapping System

Blender made another change to their API in their development branch 2.74.4 to include MultiView. That change caused YafaRay to render black images despite being working fine.

Very kindly Jens Verwiebe sent us the fix for Blender Exporter so YafaRay can work again with Blender 2.74.4. This fix is not a full integration in the new MultiView functionality, it just allows YafaRay to work again with Blender.

More changes in this beta3 version:

• Fix for -NAN results in the Bidirectional integrator when using Architectural, Angular and Ortho cameras.
• Fix for problem with Rough Glass too bright when dispersion is enabled. See: http://www.yafaray.org/node/642
• Extended Texture Mapping system (very experimental!!), allowing using textures to map additional properties in materials, to be able to create either more realistic or more exotic materials and reduce the dependency on the "blend" material. More information in: http://www.yafaray.org/community/forum/viewtopic.php?f=22&t=5091

Important note: when using some of the new mappings, the renders may slow down. I'm not sure whether it's because of the additional calculations (very likely) or if it's something we can optimize further in the future. In any case, it should only be noticeable when using the new mappings, and I think it's worth the ability to create new materials now.

The new texture mappings in addition to the existing ones are:

• Diffuse Reflection Amount in Shiny Diffuse, Glossy and Coated Glossy materials
• Sigma factor for Oren Nayar in Shiny Diffuse, Glossy and Coated Glossy materials
• Filter color in Glass and Rough Glass.
• IOR refractive factor in Glass and Rough Glass. The texture amounts are added to the IOR of the material.
• IOR refractive factor for the Fresnel in Shiny Diffuse and Coated Glossy materials.
• Roughness factor in Rough Glass material.
• Exponent factor in Glossy and Coated Glossy materials
• Mirror amount in Coated Glossy materials.
• Mirror Color in Coated Glossy Materials

I also added a (non-texture) mirror amount slider in the Coated Glossy material

Unfortunately due to Blender API limitations, in some of the new texture sliders, the "tooltip" information that appears when hovering the mouse over the slider, can be misleading and not represent the actual function of that slider. However, I took care in setting the description correctly so just by looking at the slider itself you can see what does it map.

I hope you like the changes and also that the new changes do not introduce new issues.

Best Regards. David.

Auto Shadow Bias calculation. Fix for bad NaN normals

Automatic calculation of Shadow Bias and Minimum Ray Dist depending on the scene size, to avoid black artifacts in big objects.

This is a very experimental feature that may introduce some artifacts to the images. We need to test thoroughly but seems to be working ok for now and fixing most of the black artifacts. I have seen some new minor white artifacts in some cases but they seem to go away with AA.

Also, fix for bad NaN normals that can happen sometimes.

New Clay Material, Oren Nayar sigma texture, neg color Musgrave fix

Version change

 Changes to be committed:
	modified:   include/yafray_constants.h