The knotty issue of wool… well, on the left, a Bryce primitive which can handle volumetric material, on the right, a mesh object (one of the additional primitives by Rashad) which can’t. The same material is applied to each.
In order to make Vickies jacket act like the material on the left, multiple shells are needed stacked about 20 deep with an equivalent 2D blended transparency material applied (world space mapped). This is possible… but not practical because, one 50 pixel by 50 pixel square of this material in the same light environment as shown would take days to render. The reason being that each layer requires a +1 increase in maximum ray depth which in turn sends the TA render mode off looking ever deeper into the scene for more light.
This suggest several improvements, the obvious being better handling of volumetric materials with meshes - which is already well represented in Bugtracker by Clay and myself. (note also the clipping issue where the volume material touches the ground you see some light pixels)
Also… Len’s idea for more selective render settings, so a max ray depth for TA and another for other types of light simulation. That would be super.
On a different topic… back in the world of hard edged materials. I’ve remade the handle somewhat.
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