additive, subtractive & multiply means

[leigh]

In which program?

[Dipesh (India)]

max5:p

you can surely answer my question leigh... plz help
i m talking about the transparency controls on the extended rollout of materials for transparency

[leigh]

Well, I personally don't use Max, but generally those terms mean:

Additive - multiplies the texture layer by the opacity of the layer. It basically just adds the values from the texture to the underlying ones, according to it's opacity setting. I guess this could be similar, although not quite the same, as the Dodge blending mode in Photoshop.

Subtractive - subtracts this layer/colour from the underlying layers. Basically, the colours found in this will be subtracted from the layers beneath it, where they show.

Multiply - basically multiplies the colours of underlying layers. If there are dark colours in this layer, it will make dark colours in the layers beneath it darker, while lighter colours will become lighter.

However, these are purely from my experience with other programs.
Surely this is covered in the Max manual? :shrug:

[-wT-]

Ah, I just love to hijack peoples threads... so here we go again :)

As you Leigh know LW and Photoshop so much better than I, I just wanted to ask if Photoshop had a function to substract one layer from another? Yesterday I tried to make my own GI-pass from a rendered image by saving a couple normal channels trough one of those plugins, and then tried to substract those channels from the final image to get the GI-pass... but I couldn't find anything substract-related anywhere :hmm:

Oh and then, is there a way to save the GI-pass straight from LW? Damn I can't remember the name of those plugins, but you know the ones which you include to the scene and you can pick if you want to save the diffuse/specularity/shadow/etc passes and the ones you select appear on the image viewer.
Well none of those plugins let you save the GI-pass... atleast to my knowledge, so is there a simple way?

[leigh]

Hmmm...

In Photoshop, the Difference and Exclusion blending modes are kinda similar to subtracting, but not *quite* the same.

As for the dilemma you are having with the GI pass - I don't know of any render buffer plugin that can save the GI seperately. Why do you want to do that though? I can't quite fathom why you are wanting to have your lighting information seperate...

[-wT-]

Well no particular reason, I was just experimenting... I think I'm going to try with those blending modes once more, I haven't fully understood how the blending between layers actually work, so I could've just done something wrong back then.

But hey, thanks Leigh :thumbsup: and sorry Dipesh :)

[Dipesh (India)]

thanks leigh... but i m still confused...
does actually multiply means ,, i mean what it do exactly so that we can predict that if i do this that will happen

[playmesumch00ns]

as far as I remember, MAX's blending functions are like OpenGL's. When MAX renders a pixel it compares the point being shaded with any points behind it in the same pixel and uses the blending function to work out their contributions to the final colour.

If Cs and Os are the colour and opacity of the point being shaded, and Cd and Od are the colour and opacity of the point behind, then the resulting colour, Cr is worked out like so:

Additive: Cr = (Cs*Os) + (Cd*Od)

Subtractive: Cr = (Cd*Od) - (Cs*Os)

Multiply: Cr = (Cd*Od) * (Cs*Os)

The opacity's actually blended in the same way as well.

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