Alpha Sorting Unity- Broken

Ruz

There still seems to be no solution to this in Unity ie proper 'soft' alpha hair sorting

Even with HDRP hair shader there are issues(ie it broken). The only way to make it look half decent is to use

Alpha Clipping or Alpha Test, which it is known as in some other packages

There was a shader a while back which seemed to work okayish, think it was called hair shader 1.0 or similar but seems not

to work any more

thomasp

Is there any engine that uses what you call 'proper' transparency?

All I know is dithered alpha, the type you can find in e.g. Unreal, Blender viewport, Marmoset and from the looks of it just about any inhouse engine used to render hair (clearly visible in e.g. ND's games, Tsushima, Death Stranding, RE, FF, etc).

This might be relevant: https://github.com/gkjohnson/unity-dithered-transparency-shader

Ruz

well i k now it's a problem with game engines. I know about dithered alpha, but didn't know blender used it as it looks pretty nice in eevee -

there is an option for alpha blend or alpha hashed, boith look correct sorting wise

Hair in unity loook terrible when set to transparent, bit i need that soft look. will check out that link thanks, might be good enough for what i want

some people use substance shaders in Unity, and this project uses it too, but don't have much more info on the technique. looks goodish though

https://www.artstation.com/artwork/83EBx

DavidCruz

idk if this will help but on the code side of the forums there is some sticky talking about the blend files stuff:
https://polycount.com/discussion/180954/alpha-blend-source-destination-matrix
I've never played with this is am just bringing to your attention if for whatever reason you've never seen that side of the forums which i'd believe you have. (i think of this as 'hey, i tried') if you have.

Ruz

Thanks David , i will put that in my 'use my brain' folder soon. I really did not want to think too hard on this subject

but I am making a bit of progress so far with the HDRP hair shader

It can kind of combine soft alpha with alpha test and it looks almost ok ie no zfighting, but its not perfect

I just have to read up more on what the shader is actually doing or at least certain aspects of it

poopipe

Dithered alpha test  is the conventional solution and it works pretty well 

An alternative is a 2 pass shader where the first pass is alpha tested  and the second is alpha blended 
You still get sorting issues with the alpha blended parts but the bulk of it sorts properly and you aren't forced to use TAA

Its somewhat costly but if you don't have TAA to smear the dithers it's a less shit solution than just using an alpha test 


Edit:. Didn't read your last post . .  It's probably doing that

Ruz

yes poopipe, it seems to have both options, but I could do  a layered lit shader I guess but

the hair shader is just about ok for what i need ie enable both transparency and alpha test in the shader.

has a bunch of other parameters which seem to help  a bit, like depth write etc its not perfect, but not awful

Eric Chadwick

Put some info and pics/links here that might help http://wiki.polycount.com/wiki/Transparency_map#Alpha_To_Coverage

Ruz

cheers Eric, will have  a look at that, though I don't think that technique is fully implemented yet in Unity ,(though I could be wrong)

Made a lot of progress since my last post, got to grips with path tracing in Unity. I must say it compares well to a cycles render,, but  jeeez Unity has more menus than a a restaurant, could be organzied a bit better.

RN

Ruz said:

well i know it's a problem with game engines. I know about dithered alpha, but didn't know blender used it as it looks pretty nice in eevee -

there is an option for alpha blend or alpha hashed, boith look correct sorting wise

In Blender the alpha hashed shader mentions this paper here, "Hashed Alpha Testing".

The shader itself is this (note, GPL-licensed): https://github.com/blender/blender/blob/594f47ecd2d5367ca936cf6fc6ec8168c2b360d0/source/blender/draw/engines/eevee/shaders/prepass_frag.glsl#L14

It's different than dithered alpha (aka screen-door transparency). Hashed alpha from that article seems to be an alpha test where the reference value you're testing against changes, depending on the position of the vertices of the triangle being drawn. It looks like a random alpha test, but without as much noise between frames.

Ruz

RN - alpha hashed in blender looks spot on, wish unity had that too, but I get pretty niceish results by using path tracing.
Unity with ray tracing looks pretty awesome i think