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What is the best method for (Textures/Decals) with alphas in 3Dsmax?

OccultMonk
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OccultMonk interpolator
I am texturing a hard surface modeled figure and want to add decals in a separate layer (Graphics etc). What is the best method for adding the decals?

I know I have to use to Bitmap inputs (One for the image RGB with the pre-multiplied option disabled) and one for the Alpha (With Mono Channel Output on Alpha). Then use the Alpha in the opacity slot of the material. Only there is a problem with Premultiplied/Not-Premultiplied alphas.

For example I would like to add a worn sticker graphic with multiple colors and an alpha where the sticker is worn. But There will always be multiplication with the background (For example black or white) Can you export a true Non-premultiplied alpha from Photoshop? I tried it with a TGA and PNG with a transparent background in Photoshop but did not get good results.
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  • GeeDave
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    GeeDave polycounter lvl 11
    This is often an issue, and I'm no expert on the matter but you could try looking into edge padding your decals in photoshop. People talk about Xnormal having an edge dilation feature in photoshop which might be worth looking in to if you've got that installed, there's also "solidify" from here:

    http://www.flamingpear.com/goodies.html

    Which I guess does the same thing.

    As for applying your decals onto an object, if this is just staying in Max I would probably go the route of a blend material, using your decals on a different channel.

    Ancient tutorial here:
    http://garydave.com/2010/08/adding-decals/
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  • OccultMonk
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    OccultMonk interpolator
    Thanks for the reply. I thought about the dilation feature/edge padding. But it adds an extra step and is far from perfect when decals are close together for example.

    I already apply the alphas using the Vray blend material. The problem lies with the difference between Straight (un-premultiplied) and premultiplied alphas (where the background color is combined with the image. Formats like TGA have the alpha in a separate channel and are therefore naturally pre-multiplied. While a format like PSD or PNG can have straight alphas (save with the checkerboard background). There the alpha is not in a seperate channel.
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  • Noors
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    Noors greentooth
    Your decal should not have a white or black background, the color should extend to where the alpha is full black, hence Xnormal dilatation filter.
    Btw, as long as everything is on the same layer, you can set the padding to the maximum, there won't be overlapping between shells.

    from another thread, way it should be :

    2012-10-11_1226.png

    If your diffuse is already premultiplied against the background, you'll always have a black/white outline.
    So i'm sorry but http://garydave.com/2010/08/adding-decals/ is a terrible example :p

    Post pics of your stuff anyway, it's a bit hard to be more specific.
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  • GeeDave
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    GeeDave polycounter lvl 11
    Noors wrote: »
    So i'm sorry but http://garydave.com/2010/08/adding-decals/ is a terrible example :p

    Using a blend material to apply decals is a terrible example?

    Edit
    That was in reference to simply applying the decals, I already addressed the edge dilation.
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