Fur Variance Problem

[danielreple]

Hello everyone,

I'm studing VRay Fur paramethers and think I face with some problems on Variance. When I change the vallue of Direction variance, it seams like to work like Gravity. And when I change de vallue of Gravity variance, it seams not working.

Here are the tests I did on Direction and Gravity both on Variance:

Fur_Direction: 0,0_0,4_1,0

Fur_Variance_Gravity: 0,1_0,5_1,0

Many thanks in advance

[Peter.Chaushev]

Hello, Daniel,

The Direction variance parameter controls the individual deviation from the Gravity Direction vector of each individual strand.
The Gravity variance parameter multiplies the Gravity strength value by a random amount for each strand.
The Bend parameter controls the ability of all strands to bend. The lower the value, the "stiffer" they are. (On a side note, strand bending is also affected by the VRayFur number of Knots.)

If Gravity or Bend is set to 0, all strands will point in the direction of the surface normal. If both values are differ from 0, strands will bend accordingly towards the gravity force vector which is set through Gravity Direction in V-Ray Fur's Options section

The reason Gravity variation seemingly does not work in an example like yours is because the surface normal and Gravity vectors are coincident and the default Gravity values are not high enough for noticeable differences unless compared using the VFB History toolset.
Try higher Gravity and/or Bend values to see more pronounced differences in your experiments with the variance parameters.

Kind regards,
Peter

[danielreple]

Hello Peter,

thanks for the answer!

Using your explanation, I tried some more things, but I stil havent noticed the influence of Direction Variance.

Wold you have an exemple of this working?

Note: I havent tried anything else in Gravity Variance yet.

What I've tried:
1. Direction 0 and Gravity -3 | Direction 0 and Gravity -5
2. Direction 0,5 and Gravity -3 | Direction 0,5 and Gravity -5
3. Direction 1 and Gravity -3 | Direction 1 and Gravity -5
4. Direction 5 and Gravity -3 | Direction 5 and Gravity -5
5. Direction 10 and Gravity -3 | Direction 10 and Gravity -5

Thanks

[Peter.Chaushev]

The difference in Direction variance values is definitely evident between your images (apart from the extreme values of 5 and 10, in most cases there is no need to use any > 1).
If you mean that Gravity does not do much difference between values of -3 and -5, this is normal for stanard Bend value (0,5). Increase it to 1 and you'll notice the changes in Gravity value will be more pronounced.
You can easily compare results by using the VFB History tools (https://docs.chaosgroup.com/display/...VFB-VFBHistory).
Below are 3 simple illustrations:
a) Direction variance 0.05 and Gravity -3 ; b) Direction variance 0.05 and Gravity -5 ; c). Direction variance 0.5 and Gravity -5


Kind regards,
Peter

[danielreple]

Thanks Peter, now I understand the diference of Gravity and Direction and I managed to make Gravity Variance work!

In my opinion, it's very confusing how the Direction parameter works. At first look and also reading the explanation box (Allows the user to add variance to the direction of the fur strands), what we undertand is that it will control the direction variance that fur strands blend, similar to Bend Direction Map but without map, I think it wold be more usefull if it worked like that.

Thank you very much for your great help!

[danielreple]

Hello Peter,

please, could you help me with another problem I'm having? I can't make V-Ray Fur follow the displaced object's geometry.

Before this, I couldn't get Displacement to work, than I discovered that now (vray 3) we have to apply the material to the group (from outside the group), like pabloarias did here:
https://forums.chaosgroup.com/forum/...656#post976656

With displacement working, I started to study Ignore Parent Mesh Displacement parameter and even if it is unchecked the Fur doesn't follow the displaced object's geometry. I tried to active this parameter and still having the same. I also tried in a new project and got the same result.

Regards

[Peter.Chaushev]

Thank you for reminding us about this!
The Ignore Parent Mesh Displacement parameter is currently not working. To make it functional an extensive under-the-hood change is required. This is scheduled for the next major V-Ray for SketchUp release.
In the meantime, the parameter will be hidden from the UI in v3.60.03.

Kind regards,
Peter

[danielreple]

Peter, thanks for the reply!

[danielreple]

Peter, the "Map Channel" parameter is not working too?

[Peter.Chaushev]

It does function. Keep in mind, however, SketchUp can utilize only 2 mapping channels - one applied to the front and another to back face respectively.

Kind regards,
Peter

[danielreple]

I made an article trying to explain as much as possible about vrayfur. It is written in Portuguese, but it is possible to translate using Google Chrome: