baking (fur) shells, turning a 3D volume into a series of stacked planes w/ alpha

jgarrison

Hi all, long time lurker. I looked around and found some examples of someone attempting this in Blender (in like 2007) but no recent examples. Here's where I'm at:

I wanted to see if it would be possible to quickly bake something very complex (like FiberMesh fur/hair, for example) to a fur shell. The idea would be that each face would only receive alpha information from the parts of the object closest to it. My first attempt, baking alphas from a skewed cylinder onto the planes: 

Not what I was looking for. I figure that the baking angle is determined by the face normal, so I fiddled with the normals for a bit (with little difference) and then I tried extruding each of the planes out into rectangles and baking:



This is... weird, but a bit closer to the desired result. Finally, I tried using a different baking process, height, and using the height map as an alpha. After messing around with it in photoshop for a minute, this is what I got:


Yikes, but still it feels like I'm on the right track, although I don't know where to go from here. Has anyone tried this before, and if so, what am I missing?

(btw i've seen the fluffy fur tutorial and the Ryse Moss tutorial, I know that's how you're supposed to do fur shells. I'm pursuing this method because I want to get closer to the combed look of the shells in SOTC)

EDIT: wow, I think I might have found the solution! From this wonderful tutorial by Andy Bruning: https://cdna.artstation.com/p/assets/images/images/003/041/788/large/andy-bruning-lion-tutorial.jpg?1468891162

'Make the fibers (or whatever you're using) gradient from root to tip, then bake a diffuse map and use curves in photoshop to create seperate alphas.' Makes sense, and I'll edit this again if it works out. I'd still appreciate any comments on the subject that might save me a headache.

thomasp

the combed look of colossus' fur was achieved by offsetting the various fur layers gradually from root to tip. sounds like a ton of work back then but with the smooth silhouettes we expect today i assume you're also looking into some sort of styling tool. 6 or 8 layers won't cut it and with alpha diithering it will probably look pretty messy on screen.

i've not followed this development but shots like that of the revamp https://media.playstation.com/is/image/SCEA/shadow-of-the-colossus-screen-01-ps4-us-08sep17?$native$ to me make it look as if they resort to just using alpha cards/strands nowadays. i think the furry parts on the last guardian creature's head are done the same way - with cards (over a matching fur texture on the body). styling that is rather trivial.

not played any of these up close, just looking at videos here though.

jgarrison

thomasp said:

the combed look of colossus' fur was achieved by offsetting the various fur layers gradually from root to tip. sounds like a ton of work back then but with the smooth silhouettes we expect today i assume you're also looking into some sort of styling tool. 6 or 8 layers won't cut it and with alpha diithering it will probably look pretty messy on screen.

i've not followed this development but shots like that of the revamp https://media.playstation.com/is/image/SCEA/shadow-of-the-colossus-screen-01-ps4-us-08sep17?$native$ to me make it look as if they resort to just using alpha cards/strands nowadays. i think the furry parts on the last guardian creature's head are done the same way - with cards (over a matching fur texture on the body). styling that is rather trivial.

not played any of these up close, just looking at videos here though.

I've looked into combing a fur shell like team ico did, I think some kind of plug-in is necessary to connect the shells together with edges and maintain the length of edges inbetween shell layers. Maya won't let you connect geometry like that as-is afaik.

You're right, the only thing most AAA games seem to use fur shells for now is stuff like jacket linings and so on. Yes, TLG used cards for the feathers. As for the SOTC remake, those don't seem like cards, or at least not JUST cards... if I didn't know any better I'd say they were fibers :O I'll have to look into it!

Axi5

The remake looks like it uses actual hair splines or something:

https://www.polygon.com/2018/1/30/16946392/shadow-of-the-colossus-review-remake-ps4-playstation-sony

Look at one of the full frame shots halfway down the page, those hairs are individual, most probably a LOD though.

thomasp

ah yes, nice. could it be tress-FX or an inhouse software essentially doing the same thing? https://en.wikipedia.org/wiki/TressFX
i have no experience with it but it seems to allow a mix of cards and strands: https://cdn.wccftech.com/wp-content/uploads/2015/03/Dawn-Engine-4-740x416.jpg

ZacD

Sometimes Shadow of the Colossus remake looks like it's using flat cards, others spline thicken, and other times it looks like spline clusters where one spline is controlling a patch of hair. There's sometimes an angle that makes the hair look really thinned out in spots, especially when the camera is close up.  Would be nice to see a tech break down.