[w i l l]

Coming from a background of Solidworks/Photoworks rendering when first reading through posts on this forum it was like trying to decipher code. I have managed to roughly figure out most terminology, especially relating to Maxwell. However I still struggle to userstand the exact definitions and differences beween terms such as clip mapping, weight mapping, normal mapping and particularly rendering an alpha channel... what is this used for?

Could anyone recommend any online links to rendering terminology/books that specifically explain the differences in these terms and how/when each is used (not just a Wiki definition)?

[Mihai]

You can find plenty of info on Google but for starters:

alpha channel - it's a black and white image (can hold 256 grey levels) that gets added to the images usual RGB channels. You can use it as a mask to specify which parts of the image should be transparent and which should be opaque. For example you render a house with the physical sky, then you want to cut out just the house so you can paste in another sky. So the alpha channel will look like the silhouette of the house which enables you to quickly load the alpha as a selection in PS, then copy just the house to a new layer.

clip mapping - it's a black and white image (only full black or full white, no grey levels) that can be added to a material to specify which parts of a piece of geometry should be visible or not. For example tree leafs. You usually apply a texture of a leaf to a plane. With the clipmap, you specify in the material that only the part of the plane where the leaf color texture is, should be visible. The clipmap in this case will look like the outline of the leaf (leaf itself will be white, the rest black). In Maxwell you add this clipmap in the transmittance channel.

weight mapping - This term is relevant to Maxwell, it is again a black and white image (with 256 grey levels), which you can use to blend between two or more bsdf's. You can add a weightmap to each bsdf in Maxwell. More white in the weight map means that particular bsdf will have more influence. So instead of just specifying an overall numeric weight for each bsdf, you can use a weightmap texture to describe how the bsdfs should be weighted.

normal mapping - basically it's a better version of bumpmapping. A bumpmap is a black and white map, which only gives height information to the renderer (if map more white, make bump move outwards, more black, push inwards, or reversed, depends on the renderer). A normalmap on the other hand also tells the renderer in which direction the "bump" is pointing so it gives you a better bump effect than bumpmaps. Usually a normal map is created from a highrez model, then you apply that normal map to a low rez version of the same model, and when rendered it will look in most circumstances almost as if you had rendered the highrez version. Normal maps are in color, a mix between red, green and blue colors. More info here for example: http://www.ionization.net/tutsnorm1.htm

[w i l l]

Ok thanks Mihai!

So does that mean that a displacement map is a better version of a normal map?

[-Adrian]

Displacement is entirely different again, if it's vertex displacement is actually moves the vertecies on your mesh, if it's the nowadays more common micropoly displacement it creates additional geometry to create surface detal.

Normal mapping does not change the geometry at all and is thus preferrable whenever applicable.

CG folks are still working to improve these things and have created mapping methods that allow for displacement-like looks with a comparably very low memory footprint, still a work in progress i guess.

[glypticmax]

Ok thanks Mihai!

So does that mean that a displacement map is a better version of a normal map?

Displacement maps can also be *baked* so you can alter the geometry of your model. Not useful if you are just modeling for a render, but essential if you are going to be rapid prototyping or milling your model for production.