This is simply an explanation of the SLA shader Buffy, seeing as so many people keep asking the same question, i.e. "What is Buffy?".
A very simple explanation is that Buffy is a two sided shader, on the front side it's white, on the back it's black. Ok so what does that mean in real world terms? Ok the simplest way of explaining this is to do a couple of examples.
Example (a)
Firstly add a plane object. Now make a new material. In the Colour channel add BhodiNUT Buffy. Apply this to the plane. Now do a couple of renders. One from the front of the plane, and the other from the back. Ok so now you see what's going on with this apparently simple shader. On the front it renders white... no the back render it's black.
Ok so that shows clearly that the shader shades one side white and the other black... but what happens with a more complex shape? Would a sphere be half black and half white? The answer is no. As far as C4D is concerned there is no front and back to any object, the only things with fronts and backs are Polygons.
Ok so to demonstrate this, and to show what would happen if you were to use Buffy on a more complex object here's the second excercise.
Example (b)
Create a new scene. Add a sphere object and add a sky object. Create a new material and in the Luminosity channel use BhodiNUT Buffy, then activate the alpha channel and use BhodiNUT Tiles. Change the tile settings to Lines 1 change the colours to be Black and White, and remove any Grout or Bevel (bring them down to 0%). Apply this to your sphere.Now render. You will see that the bits of the sphere that you can see through the lines are black, while the front is white.
Next make the sphere editable, and go to Structure->Reverse Normals. This will flip the polygons in the sphere. Re-render.
So what has this demonstrated? The fact that Buffy is linked to the way that the polygons face.
This is all... what next? That's all very nice and what have you, but why Buffy? What practical use is it?
Buffy is good for a number of things, but the most obvious one is creating solid looking transparent objects.
Why is this? Well the most obvious thing is to look at something glass... if you have a nice blob of the stuff then that's even better. something like a crystal ball is ideal for this. But if you look at that then you will notice that if it's perfectly clear without any real grub on it (i.e. dust) that there's no Specular Highlight on the interior of the object, only on the front side. If you see a specular highlight through the object then either clean it or try to make sure that there's nothing near the other side where the specular highlight appears. You should find that the only highlight on your object is on the front... getting an idea now?
Example (c)
Taking the last scene, map any texture you want onto the sky, and then for the sphere reverse the normals back to what they were, then adjust the Material as follows:
Switch off the Colour and Luminosity channels, switch on Transparency and set the Index of Refraction to be around 1.6, this is a moderate to heavy glass (for a complete lookup table of index of refractions check here (http://hyperphysics.phy-astr.gsu.edu/hbase/tables/indrf.html)) Tick fresnel. Go to the Specularity tab, and bring the specularity brightness right up to around 150% (we're not creating a realistic glass here, just something for an example). Make sure that only transparency and the specular colour are on.
Next to show the specular highlight add a simple Omni Light and move it to a position where you will be able to see the specular highlight clearly, and render.
Ok so now you're seeing that this looks like either a very dusty peice of heavy plastic, or a bubble. So you can guess what's going to happen next right?
Go back into the material for the glass/plastic, and switch the Specular Colour channel on, in this channel apply BhodiNUT Buffy. Now re-render the same scene.
So suddenly it looks solid right? Well at least a little more solid than it did. So what's going on here? Where the specular colour is black of course it doesn't render as a black specular channel, a specular highlight with a black specular colour simply doesn't render, because specular highlights are addative. So then by putting Buffy in the specular colour channel you're able to make the material only specualr on the outside (or if you were to reverse the normals only on the inside). You can also apply this to the colour channel if you want to have some dustyness on your sphere (but don't forget to tick additive in the Transparency channel).
Buffy and other textures
So this is all well and good but just black and white are a little limited. What about other materials... or even textures?
Buffy will help you here, but you will also need to use fusion. Make a fusion channel and put Buffy in the alpha of the fusion, then simply put the texture/colour you want for the front in the top channel, and the texture for the rear in the bottom channel of the fusion. You should now find that you have the level of control you had before only you're now dealing with two textures, the front and the back texture. This doesn't have to be purely for transparent materials. What about making a playing card in one texture front and back. Place the front image map into the top of the fusion and the back image into the bottom of the fusion... problem solved.
With careful thought buffy gives you two textures applied to one surface with one texture tag.
I hope that this clears things up for people and that now you will all have some idea about what Buffy is, and it's uses.
Please Comment on this post
Thanks
