Kristinka Hair Tests

Comments on work in progress
User avatar
rray
Moderator
Posts: 1385
Joined: 26 Sep 2009, 15:51
Location: Bonn, Germany
Contact:

Re: Kristinka Hair Tests

Post by rray » 25 Apr 2010, 18:05

Well done, Anto!

Sorry everyone for the lack of updates (and the tutorial) . . Need to get back on track.

Here's a scene file for the last picture I posted (SI '11 format)

Btw: Did anyone notice improved render times when using ray tracing with strand hair in SI 2011? By some first tests, it seems to be faster than rasterizer now compared to SI 2010. Might be some glitch in my setup also.

Btw Anto, AbsoluteShapeWidth seems to change the look of the render also, I can't get it to look the same as when rendering with Pixel Units. It looks a bit more like wires than hair.
IMG_H1.jpg
Test: two pointclouds with diff. hairstyles merged
IMG_H1.jpg (85.42 KiB) Viewed 3470 times
Softimage Resources section (formerly known as rray.de/xsi) updated Oct 01 2017

User avatar
Mathaeus
Posts: 1660
Joined: 08 Jun 2009, 21:11
Location: Zagreb, Croatia
Contact:

Re: Kristinka Hair Tests

Post by Mathaeus » 08 May 2010, 22:20

Hi,

here is a small experiment with final gathering and ICE strands. For ICE strands, I think it's good idea to always use 'Long Hair' diffuse model in Hair Renderer -
not only because long hair is modeled. Even with short hair, info about normals from emitter's surface doesn't exist (at least I think so). Also, Kristinka Hair nodes does not respect old fashion hair shading rule of 'first segment parallel to emitter's normal'.

So, 'Long hair' diffuse model calculates shading normals relative to direction to lights - but in case of final gathering, what normals are used ? I'm still not sure, to be honest. For this experiment, I've used only one light with very low intensity, didn't noticed any influence of this one to FG shading.

Fortunately, we can provide a custom shading normals to Hair Renderer. Custom vector is used as an input for 'normal' in Bump Generator node, as well 'Relative to Input Normal' option with node. 'Bump Factor' is set to zero, as we already can't use bitmap, there is no 2d mapping with hairs, only normals are important here. To get it work, 'Normal Blend' in Hair Renderer need to be at more than zero.

Now, examples. Two at bottom are Eye Ray Vector - normal are looking at camera, or inverse. Second one looks most promising to me, it's custom attribute already created by kH Follow NURBS styling modifier - this is in fact, surface normal of NURBS surface used for styling, sampled for each strand segment of hair guides, then transferred to rendered strands/hairs. This is fast setup, of course it's possible to create a more fancy solution, with complex setups.

Cheers

Image
The renderer "turtle" used by this scene, is not currently available. The "turtle" renderer will be used instead.

User avatar
rray
Moderator
Posts: 1385
Joined: 26 Sep 2009, 15:51
Location: Bonn, Germany
Contact:

Re: Kristinka Hair Tests

Post by rray » 09 May 2010, 01:44

Interesting, it never occured to me that this is even a problem before xD

Wouldn't the best normals for fg be:
(walking along the width of a strand) ...
cross product of inverse eye ray and strand segment's direction vector----> inverse eye ray ---> inverse of the cross product

Maybe this could be simulated ...
Beause fg samples a hemisphere this would result in a total 360 degree sampling (with prevalence towards inv. eye)

I tried to test this by merging the last two of yuor pictures in photoshop (inverse eye ray normal at 66% blend mix, eye ray normal at 33%)

Hm ah well... no idea if this looks any more realstic, probably some more renders and teting required ~o)
hairblend.jpg
hairblend.jpg (63.04 KiB) Viewed 3419 times
Softimage Resources section (formerly known as rray.de/xsi) updated Oct 01 2017

izze
Posts: 171
Joined: 24 Sep 2009, 20:02

Re: Kristinka Hair Tests

Post by izze » 11 May 2010, 00:32

Could I ask where to find AbsoluteWidth and Pixel Unit settings? I am having difficulty finding more information regarding this option.

User avatar
rray
Moderator
Posts: 1385
Joined: 26 Sep 2009, 15:51
Location: Bonn, Germany
Contact:

Re: Kristinka Hair Tests

Post by rray » 12 May 2010, 22:42

There's no setting, you'll need create a set data node and set shapeSizeAbsolute true for each particle
Softimage Resources section (formerly known as rray.de/xsi) updated Oct 01 2017

izze
Posts: 171
Joined: 24 Sep 2009, 20:02

Re: Kristinka Hair Tests

Post by izze » 13 May 2010, 00:57

Thanks for getting back to me on that.

I just spent the last 48 hours trying to pin down a problem I am having. I am getting crashing during render time in 2011. I think I have it narrowed down to a combination Kristinka, SSS, and Final Gather.

I can have SSS and Kristinka in the scene without problems, but once I turn on FG my renders lock up or crashes XSI. Also, I can have Kristinka and FG, but once I introduce SSS to the scene, I get the same problems. I have tried this on several machines in our office. For testing purposes I am using the built in fast sss material.

This is only in 2011, so I apologize if Kristinka is not ready for 2011, or if I have missed information indicating this issue. (or otherwise just messing things up myself) :)
Attachments
2011 Hair Test.rar
(162 KiB) Downloaded 165 times
2010 Hair Test.rar
(138.81 KiB) Downloaded 141 times

User avatar
Mathaeus
Posts: 1660
Joined: 08 Jun 2009, 21:11
Location: Zagreb, Croatia
Contact:

Re: Kristinka Hair Tests

Post by Mathaeus » 13 May 2010, 10:07

For me, it looks like Mental Ray can't handle combination of SSS, Hair primitives an FG, where each of these components isn't problematic itself. From my experience, problems can happen in areas with high strand's density - Mental Ray became deadly slow, or you can see a 'lovely' message about firing another 1000 FG points.... then it hangs.

Usually I'm able to solve this by setting 'Max Depth' value in global Rasterizer's render options, to something more than zero - let's say 20, 30.... Avoiding to use transparency on ICE strands, where ever you can, it's also good idea.

Kristinka Hair ICE nodes are just XML, textual files, that communicates with ICE in any XSI version you have, above 7.01. I don't planning any serious updates in near future.

Thanks
The renderer "turtle" used by this scene, is not currently available. The "turtle" renderer will be used instead.

User avatar
Werner
Posts: 157
Joined: 09 Jun 2009, 13:30
Contact:

Re: Kristinka Hair Tests

Post by Werner » 13 May 2010, 18:59

The same thing is happening to my scene. Skin shader, strand hair and FG is a no-go. It's not a problem to split objects up in passes, but FG with Strand hair takes 3 - 5 times as long to render (with SSS objects hidden). We had to dump Mental Slow FG for this project.
Also, I did some render benchmark tests and found that Raytracing was faster then Scanline or Rasterizing. I stopped the render on Rasterize because it took way too long. I must be doing something stupid.

User avatar
Mathaeus
Posts: 1660
Joined: 08 Jun 2009, 21:11
Location: Zagreb, Croatia
Contact:

Re: Kristinka Hair Tests

Post by Mathaeus » 13 May 2010, 21:18

Guys,

I need to say that all images I've posted, were rendered with XSI 7.01. Also, I didn't used mi_sss_skin shader, anywhere. Subsurface is done with some kind of ICE vertex color 'shaders', a bit improved version of these.

If anyone is interested, I'll post last version - these 'shaders' are maybe harder to figure out, there is no 'real' connection to lights or FG - but output is a much lighter for Mental Ray, just vertex colors are rendered.

Cheers
The renderer "turtle" used by this scene, is not currently available. The "turtle" renderer will be used instead.

User avatar
rray
Moderator
Posts: 1385
Joined: 26 Sep 2009, 15:51
Location: Bonn, Germany
Contact:

Re: Kristinka Hair Tests

Post by rray » 07 Aug 2010, 15:47

Image
Softimage Resources section (formerly known as rray.de/xsi) updated Oct 01 2017

j3st3r
Posts: 121
Joined: 11 Jun 2009, 09:13

Re: Kristinka Hair Tests

Post by j3st3r » 01 Nov 2010, 15:57

rray, can you share your setup for short hair? I wanna make a short haired guy, but I really don't know how to start... :(

User avatar
rray
Moderator
Posts: 1385
Joined: 26 Sep 2009, 15:51
Location: Bonn, Germany
Contact:

Re: Kristinka Hair Tests

Post by rray » 01 Nov 2010, 16:03

You can find the scene with the short curly hair here.
Softimage Resources section (formerly known as rray.de/xsi) updated Oct 01 2017

j3st3r
Posts: 121
Joined: 11 Jun 2009, 09:13

Re: Kristinka Hair Tests

Post by j3st3r » 01 Nov 2010, 21:08

Thanks Reinhard,

Actually now I'm in deeeeeep trouble, I can't create decent short hair with Kristinka...anybody has some idea to help me?

User avatar
Mathaeus
Posts: 1660
Joined: 08 Jun 2009, 21:11
Location: Zagreb, Croatia
Contact:

Re: Kristinka Hair Tests

Post by Mathaeus » 01 Nov 2010, 22:07

Jester,

what short hair.... if you can show some picture.... There are so many hairdos, it seems to be really hard to find an unique workflow for all.

Cheers
The renderer "turtle" used by this scene, is not currently available. The "turtle" renderer will be used instead.

j3st3r
Posts: 121
Joined: 11 Jun 2009, 09:13

Re: Kristinka Hair Tests

Post by j3st3r » 01 Nov 2010, 22:13


User avatar
Mathaeus
Posts: 1660
Joined: 08 Jun 2009, 21:11
Location: Zagreb, Croatia
Contact:

Re: Kristinka Hair Tests

Post by Mathaeus » 01 Nov 2010, 23:29

if you want to do that in procedural way .... (I believe most of people would prefer brushes from standard XSI hair, for short hair setups), probably you can try this one

Setup is a mod of 'fur from nurbs' example, with improved 'vector field' compounds. Hair's orientation is created by nulls. For now there are three options: null's Y axis as direction, direction to null itself, circle around null's Y axis. Scaling of nulls modifies the influence.
Or another one ( kH2 Vector Field by Curve) that takes direction from curve.

Nodes are new, very different than ones from last release (incompatible with 'fur' nodes...) .

I created these last Vector field nodes for fur and feathers, if this fits for hair....it would be nice.

Cheers
The renderer "turtle" used by this scene, is not currently available. The "turtle" renderer will be used instead.

Post Reply

Who is online

Users browsing this forum: No registered users and 2 guests