Transparency Gradient - possible or not ?

Kyueru

Hey guys,

So I've got this model I'm working on.
She's a humanized panda sea squirt, I really liked the design !



My model's done (except for the texture) and weights roughly 15k tris which I believe is okay. It's the first time I'm trying to do a real-time character.



Now comes my problem.

As you can see, she's got some areas where she's transparent-ish and other areas where she's opaque.

I'm currently trying to make some renders using Marmoset but I'm struggling with the transparency.
I've read on some topics that you needed to use a different material depending on which part you want to be transparent or not.
But the thing is that her body is a combination of both.
For example, from what I can see, her chest area is opaque whereas her neck and waist are transparent, allowing the skeleton to be seen.
On the other hand, I didn't connect the skirt part to the body, so it's okay to make a new material for it.

Is it possible to manage the transparency in such manner ?
I tried creating a transparency/opacity map using the alpha channel of my albedo, but I don't quite get how it works as some parts of my model keep disappearing (the parts that are black on the map).

In the end, I'd like to be able to rig and animate this character, with her textures being transparent and opaque in the right spots.

Sorry for the long post, I just feel like I'm at a dead-end at the moment and I could really use some help !
Thank you !

DavidCruz

She looks like a jelly fish, cool design, so what i would try to do is make a translucent material (shiny version of her) then the opaque version of her (faded version) under the shiny part, so you'd have to versions of her, one inside (flipped faces / scale it down a touch ) one outside (normals facing the correct direction). (if you plan to do more with her that might run you into issues.)  
Why do you want to do this? 
You want to still see her silhouette but remove the content, if you just added the alpha she would be almost invisible and you also loose the darkness you have in your concept, if you double it up you can have a windowing effect with her so you can still see a darkness but it would be see through like a tinted window.

Its an old technique of doubling the geo and flipping the faces (used to create the cartoon outline look. )

Links:
http://wiki.polycount.com/wiki/Opacity

^ I don't know if this is still true but i hear using alpha is costly on engines so if you can refrain from using it people generally do refrain from it, otherwise if its just for an image you should be alright.  Last thing is i put the alpha to R Channel (its probably wrong to do this) but i do it cause it gives me the gradient type of look (sometimes) the alpha gradient map has to be really well made to pull it off right and of higher resolution, so try to work with a high resolution with the textures before finalizing the end result.  

If you are going for a particular style (old game stuff) then do what you need to, using references helps with your goals, you didn't state the style you are after so i took it as is (unlimited - no restrictions.)

I'd go with maybe a dark green rather than straight BLACK on the color map and leave the blackness to the alpha, also make the alpha its own map (so it retains the RGB values) then put the channel to R, again its probably wrong to do this but i do it when i need that look.  Good luck maybe someone else has better methods.

Obscura

Try a not fully black opacity map.Try some dark grey. The darker the value is, the less visible it will be. Using a black to white gradient would cause it to fully disappear at the black opacity pixels, and to be fully visible at the white ones, and there would be a transition. 

There are multiple reasons to minimize the transparency area. You could indeed apply a new material to the skirt polygons, and that would make the other parts much cheaper to render. Real time transparency also suffers from sorting issues, so its the best to stay away from translucent materials, whenever its possible. This is why you can't see glass rooms and many fully transparent characters in games.