Math for Comping Elements

[Morne]

Hi all

I know this is all over the forum, but it's always a mission to find the right info, so
Please can we have a section in the help docs here:
http://docs.chaosgroup.com/display/V...r+3ds+Max+Help

...for math of comping elements to rebuild the beauty pass.

1) when to add, when to multiply
2) How to make your own RAW passes without rendering the RAW passes. Something gets devided by something etc.
3) When to use filtering and when NOT to use filtering in the element.

Alternatively, if not in the docs, can we have a sticky in the forum for this please!

[Dave_Wortley]

It's not too complicated.

Reflection, Specular, Refraction All go on 'Add' (Normal, linear add) in any order
RawtotalLIghting * Diffuse = TotalLighting
RawGI + RawLighting = RawTotalLighting


Diffuse / Reflection Filter = flatDiffuse (not normally needed)
RawReflection * reflectionFilter = Reflection
RawRefraction * refractionFilter =Refraction

[Morne]

Thanks Dave

If we can sticky this or put it in the docs so it's easy to find again it would be great!

So ignoring the RAW passes for the moment. To get the beauty I add everything?

So diffuse + gi + lighting +reflection + refraction + specular = beauty?

[Seraph135]

So diffuse + gi + lighting +reflection + refraction + specular = beauty?

Not quite right....take diffuse out of your list and then you'll get the beauty. Assuming you don't also need SSS or self illum passes. The GI and Lighting passes already have diffuse information in them so diffuse is not needed to recreate the beauty in the case your asking about.

Also, Multiplying passes like rawLighting * Diffuse is almost guaranteed to give you edge issues in your comp. Anytime your multiplying passes your likely to have edge issues. This is where dividing passes to create other passes is the solution.

One other important bit of info is that you can only comp elements together and recreate the beauty if your using floating point renders. You probably already knew that, but in case someone else reads this thread and is just starting to learn about this its a very important detail to know.

Tim J

[Morne]

Not quite right....take diffuse out of your list and then you'll get the beauty. Assuming you don't also need SSS or self illum passes. The GI and Lighting passes already have diffuse information in them so diffuse is not needed to recreate the beauty in the case your asking about.

Tim J

What if I also need SSS and Self Illumination passes?

[Rens]

Some more math for you. : )
http://forums.chaosgroup.com/showthr...845#post660845

[Morne]

Some more math for you. : )
http://forums.chaosgroup.com/showthr...845#post660845

Thanks Rens, great write-up

[Seraph135]

What if I also need SSS and Self Illumination passes?

Rens covered it in that other link, but both "should" be a simple plus as well. I have not needed to render a separate SSS pass for a while now, but I know roughly two years ago it was not adding back up correctly. At the time I was having to subtract out everything else leaving behind my own SSS element.

Tim J