Render-to-texture alpha transparency / Marmoset issue

danshewan

Okay, so I've been reading over approaches to achieving glass and other transparent effects using alpha transparency, and how to view the results in Marmoset. The process seems straightforward enough, so I can only assume that I need to up the dosage of my brain medication.

When I've finished a low-poly model, I apply a multi sub object material with basic colors assigned to make masking in Photoshop easier. I then use Render to Texture to render out a simple diffuse map (in .tga format), which will be the basis of my photo-manipulated texture.

I open the rendered diffuse targa in Photoshop, and open up the channels palette. I paint the areas I want to be transparent black, and then go back to working on the rest of the texture. However, I can't seem to get the transparency to work correctly in Marmoset.

What settings do I need to enable to see the results of the transparent effect? Is there a setting I need to check when using RTT? Is my approach totally, utterly wrong? Should I forget it all, and go pursue my childhood dream of being a stuntman?

Any suggestions or pointers to workflow overviews that are non-Marmoset specific would be most welcome.

Ben Apuna

If you're using the old Marmoset, you need to:

1. Place the opacity map (Black is transparent, white is opaque) in the alpha channel of your diffuse texture and save it as a 32bit TGA.

2. Change the Blend Mode of the material to something other than "None", most likely "Alpha" will work best.

3. Uncheck "alpha testing" in the material,

unless

You are using "alpha test" style opacity in which case all you need to do is the first step and keep "alpha testing" checked on, then slide the alpha testing slider over until you get the desired result.

If you're using the new Marmoset, you need to:

1. Place the opacity map in the alpha channel of your diffuse texture and save it as a 32bit TGA.

2. Turn on either Use Alpha Testing and slide the Alpha Threshold to the right until it works.

or

Turn on Use Alpha-to-Coverage.

3. (possibly optional) Change the Blend Mode of the material to something other than "None".

As for glass in general it's best not to paint the alpha completely black so that there is still "something" there to either reflect a cube map or show a specular + diffuse result.

I hope that helps.

danshewan

Cheers, Ben - I'll try that. I'm using the new Marmoset (for a few more days at least, until I can sell a kidney), so thanks for offering various solutions.

danshewan

When placing the opacity and gloss maps in the alpha channel of the diffuse and spec maps respectively, is this done directly in Photoshop, or using the map slots of Max's material editor?

I've been trying the latter approach, and it seems like a convoluted way of doing it, which leads me to believe I'm once again doing it wrong.

What's the best way of adding opacity and gloss maps to the alpha channels of their respective maps?

Apologies for my shocking noobishness. :poly136:

disanski

Hey danshewan. I am not sure what is the second way you are talking about, but what I do is lets say for the gloss map - just flatten all the layers of your file for the gloss map and copy it this one layer , open the channels tab and if you dont have alpha channel create new one and paste your layer with the gloss map there. I also think it might me important to save it as 32 bit tga( perhaps other file formats are being used too, but i just use tga for now). Hmm I hope that helps

danshewan

Right, that makes way more sense. Thanks.