New shaded hair composite test.

[pleavens]

Hi all,

 

I've been continuing my tests with compositing shaded hair and final renders directly in AM - no alpha channels or fancy software needed.

 

Here's the result of my latest process, the TOTAL render time for this 1024*768 image, was 6:30 on my 1.4 gig machine. That's 6 minutes, not hours.

 

This is frame 44 of the test animation which uses dynamics for the hair. I'll post a link to the final VGA animation later.

 

EDIT - Link to VGA dynamic hair video 1.03 megs Quicktime UPDATED to high density hair.

 

Link to full size version of still

 

 

Phil

[johnl3d]

wow looks great any hints on the procedure you are using

[pleavens]

wow looks great any hints on the procedure you are using

It's fairly complex, but if there's some interest I'll try and produce a tutorial on the process.

 

Short answer is...

 

Render hair shaded at as high a resolution as your system will allow, (in this case 2000*1500) with NO lights and nothing that will cause it to anti-alias. Use a copy of the model that you want for the final render, with any openings stitched closed, and all surfaces black with no falloff or specular component. Any models that will intersect (cover up) the hair will need to have this process applied. Set the camera to have a solid black background.

 

The hair material cannot have transparency, or be tapered to zero at the ends. Also, using pure black for the hair color will create problems.

 

Batch process the resulting sequence to remove the axis symbol from the left corner by painting it out black in your favorite image editor.

 

Import the edited sequence as an "on top" camera rotoscope into a copy of the choreography. Make sure the "key color" is set to black and then switch models to the originals and add lighting and such to taste.

 

Final render the composite.

------------------------------------------------------------------------------------------

The reductions in final render times are fantastic. The hair render for the animated test of this image took only 30 minutes for 60 frames to render at 2000*1500.

 

Phil

 

 

Phil

[pleavens]

Ok, the video version is now available. Total render time was about 30 min for the hair pass and 3hrs for the final VGA output at 9*9 multipass using a Jeff Lee animated skylight with one additional keylight.

 

1.4 gig machine with an OEM Radeon 9600 graphics card.

 

2 Second Shaded Hair Test Video

 

And the still

 

Phil

[JTalbotski]

Nice work, Phil!

 

I, for one, would like to see a tutorial. Any speed increases like this are very valuable.

 

Jim

[heyvern]

...Batch process the resulting sequence to remove the axis symbol from the left corner by painting it out black in your favorite image editor....

 

 

Phil

Hmm...

 

This is slightly irrelevant but can't you turn off the axis thingy?

 

I can't remember for an absolute certainty but I thought you could turn that off somewhere.

 

Would save a couple of steps.

 

I will investigate.

 

Vernon "Keep my hair in the shower drain" Zehr

[pleavens]

This is slightly irrelevant but can't you turn off the axis thingy?

Vern - It would be nice. But, if it's there I can't find it.

I, for one, would like to see a tutorial. Any speed increases like this are very valuable.

Jim - I will try to do something in the next week on this.

 

Here's a new still with the hair density increased to 300% and it's thickness reduced. Frame 13 of the animation, as it shows the hair detail better.

 

Frame 13 full still

1024*768 Hair pass completed in about 2 minutes. It was about 30 sec at 100% density.

 

 

 

Phil Leavens

[Ross Smith]

Certainly looks great, Phil.

 

I can see you circumvented issues with alpha channels by doing everything possible, as you said, to prevent anti-aliasing and using absolute black as the transparency color. That makes sense. It also makes sense that the render time for the hair would be much quicker without lighting. But doesn't that mean the composited hair layer has lighting unlike the model pass? It seems to me that only the flat, ambient light would affect the hair at that point, regardless of the scene lighting.

 

This looks like great work in fast time, but I would appreciate it if you could help me resolve this bit of confusion.

 

Also, when you render the model pass, do you disable the hair? I imagine that's a given for avoiding extra render time in the first place, unless the renderer does something I'm not aware of. (Definitely possible, since I don't really know how it works.)

 

Thanks,

Ross

[pleavens]

But doesn't that mean the composited hair layer has lighting unlike the model pass? It seems to me that only the flat, ambient light would affect the hair at that point, regardless of the scene lighting.

Ross, you are absolutely correct, unfortunately the shaded render mode does not work with ANY lights in the choreography. So currently, there is no way around it that I am aware of. Of course for stills it's possible to wait overnight (or longer) for a final render, where this really pays off is for animations where the lighting issue will be far less noticeable anyway.

Also, when you render the model pass, do you disable the hair?

Yes, as it's only being used on the black-out copy of the original model to do the shaded pass, there is no need for any of the "hair stuff" to be active on the original.

 

Phil

[johnl3d]

tried the idea om a simple test project and it worked quite well. Thanks

 

 

johnl3d

[pleavens]

I've done some more testing with interesting results.

 

New Shaded Test

 

I accidently discovered that lit shaded hair now seems to render. As it never would for me in the past, I am at a loss for an explanation.

 

Hair render type comparison

 

Here's a group shot showing the results of hair rendered using some of the various techniques as well as the total render time necessary to complete them.

 

I put more time into her hair grooming, and used some force and collision for the first time in these tests. The next step is to see how well the collision dynamics work over time.

 

Phil

[zandoriastudios]

Is there anything you can do for the lack of shadows? That is the thing that I find distracting. Maybe if you keyframe the hair brightness to make it darker near the roots to simulate self-shadowing, and put a diffuse map on the skull to make it look like the hair is shadowing the head a little.

[pleavens]

Maybe if you keyframe the hair brightness to make it darker near the roots to simulate self-shadowing, and put a diffuse map on the skull to make it look like the hair is shadowing the head a little.

A good idea, but first I would like to see some success with hair collision. I like the shape you get from lower constraint values combined with collision being on. Not to mention that Gala looks kind of funny with hairs sticking through her face and ears.

 

Unfortunately there seems to be an "undamped" quality to the hair dynamics with collision on, that totally ruins the intended effect. I am going to start some simple tests to see if I can isolate the problem areas.

 

Has anyone had success in this area? - If so, I sure would like to know how you did it.

 

Just had an idea...

I will try a composite render with "shadow" on in the hair emitter, using the final render single-pass technique. There's a possibility that I can capture the shadow data somehow. (shadow only, or to the buffer) I'll keep you posted.

 

Phil