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Brazil Utiliy and Brazil Basic

Brazil Advanced (All the Rest):

There are 5 remaining Brazil Advanced shader types: Ghost, Glowworm, Velvet, Lambert and Oren-Nayer. The first two have behavior that is specific to that shader alone, while the Velvet shader has many elements in common with the wax shader in the last tut. The Lambert and Oren-Nayer shaders are simply different shading models, but don't have any fancy features per se.

Let's start with the Ghost shader.

This shader varies the opacity of the surface based on the amount of light striking the surface. This is mixed with a self-illuminating fog inside the object. The settings for this shader are fairly basic:

The ambient and diffuse color swatches and their Ka/Kd settings work here as they do in other shaders. All that is left are two settings for the way the internal fog is to appear. The fog range control seems to really control the amount of fog inside the object, higher settings giving less fog and low settings making the fog thicker.

The last spinner for the ghost shader is the control for the 'illum effect'. This controls the illumination of the dark areas and how they act as far as opacity goes. Between 0 and 1, this spinner makes the dark areas self-illuminating and opaque (at 0) and go to non-self-illuminating and clear (at 1). Over 1 it makes the dark areas begin to light up white and become more opaque again. It also begins to have an effect on things that you are seeing through the object, illuminating them and turning shadows to the diffuse color of the ghost material, as shown on the dark-red sphere behind the teapot below.

Next on the list is the Glowworm shader. This one also reacts to illumination, like the ghost shader, although instead of controlling opacity, glowworm varies self-illumination based on lighting. This means that when in a brightly lit scene, the glowworm shader will appear pretty much as a normal diffuse shader, but when put in a dark scene, it will appear to glow a bit.

The controls for this shader are pretty basic.

The only thing that struck me as strange here, is that the incandescence color doesn't really work the way you would expect it to. What happens is like so: if your incandescense color is white or grey (rgb channels even) then it acts as straight self-illumination, dependant on the shade of grey. If you use a color, then rather then making the shader glow that color, it causes that color to be the only one affected when the diffuse channel is self-illuminated. IE, if your diffuse color is red and you use 100% blue as your incandescense color, then you will not get any glow, but if you used purple (which has some red in it) it would cause the glow on the red diffuse channel to be proportionate to the amount of red in the purple. In my example image below, the teapot has a %100 red and %100 green checkerboard pattern on it, and you can see how the different incandescence colors (little circle is the color) change which areas are illuminated.

The only other control here is the glow level, which just acts as a multiplier for the amount of glow. High numbers boost the glow affect, low numbers reduce it. Easy!

Next is the Velvet shader:

This is an older shader, the first to have the sheen highlight as an option. Since it was added to brazil, many of the other shaders now have the sheen as an option, rendering this shader a bit obsolete. There are no properties that are unique to the velvet shader now, so please refer the the section of the wax tut that deals with the sheen highlight for info here :)

The last two are the Oren-Nayer shader and the Lambert shader. These are simply different shading models for diffuse illumination. The Lambert shader looks pretty much just like the default shader, except that there are no options for reflection, refraction, self-illumination, etc. It is strictly a diffuse shader, with the option for a specular highlight.

The Oren-Nayer shader is designed for matte surfaces and has a much broader illumination model. This makes it the surface look flat and dull.

That pretty much wraps up the rest of the advanced shaders. Now, on to the last shader tut, dealing with the utility and basic materials:

>>>> Six down, one to go!! >>>>

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