Diffuse + Specular = ?

LRoy

Hey guys. I'm having a bunch of trouble with defining materials. I've watched loads of tutorials and read up on spec maps but I end up picking my colors/values through trial and error. I don't understand how the two maps work together to produce the final result. Is there some kind of formula that shows X + Y = Bronze (or whatever).

The only things I sort of get is that the more reflective the surface the darker the diffuse, but I see this isn't always the case?

If anyone could shed some light on this I'd really appreciate it.

Autocon

The best way to understand materials and material definition is not by a formula or X + Y = Z or following a guide, its by observation.

It is honestly the best way to understand materials, how they react in the light and understanding what is causing that effect. Its more then just looking at something and being like, oh hey this is shinny. Really sit there for more then a few seconds and try to understand what you are actually seeing.

edit: Look at the material and try to understand why it is scattering the light the way it is across the surface. What is the is causing this? What color if being given off in the bounce light, how reflective is it. How dark is the actual difuse color of the object and how much brighter is the light making the object. How much is being effected by the light/color of the light.

Dylan Brady

I was looking for a thread I saw on here that talked about the actual molecular propertis of gold. and why it looks the way it does.
but I found this http://www.polycount.com/forum/showthread.php?t=56483&highlight=material+definition+gold+reflection
has some good stuff.
if anyone knows what Im talking about please help me out. would love to read over that thread

equil

you can measure most of this stuff. diffuse and spec can be picked up by a camera with a polarizing filter. gloss can be measured with a glossmeter or a goniophotometer.

and yeah, this kind of data already exists and is availible for a large range of materials. here's a sample of blue acryl paint. and yeah, it's useless. you won't find a list of just "50% gloss, 10% spec, 60% diffuse etc" because that depends a lot on how your shader works. If you want to learn, don't pick up a cheat sheet, pick up a book or read some sites about material properties.

grossly simplified, diffuse+spec should never be brighter than 1. so if you add to one you should remove from the other. this doesn't really hold up, but it's ok as a rule of thumb.

PhattyEwok

This is an awesome article about spec maps and how to implement them.

http://www.manufato.com/?p=902

gsokol

The tutorial PhattyEwok posted is pretty awesome. Definitely sent me in the right direction.

Using that, trial and error, and close observation of random objects should help.

Xoliul

Thing is that the whole hue-shifting 180 degrees is not necessary anymore with shaders like mine or 3PS, so don't get confused with that...

PhattyEwok

Xoliul wrote: »

Thing is that the whole hue-shifting 180 degrees is not necessary anymore with shaders like mine or 3PS, so don't get confused with that...

Could you explain this a little more. Have I been inverting my specs this whole time when I didn't need to?