Hi,

I would like to manipulate denisty of fur clumps distribution over my object.
First idea in my mind was to change furdenisty attribute just before FUR sop node that goes to clumps. But then my overall density of fur was changed!

So how can I prevent changing overall density of fur and set my desired clumps density ?

tmdag
So how can I prevent changing overall density of fur and set my desired clumps density ?

Consider inserting nodes for manipulating the “furdensity” attribute between the “create_clump_hairs” and “merge_skin” nodes in the “clumps” object. You will likely want to modify the “clumpradius” attribute too. Be sure to include the “clumpradius” attribute in the list of attributes the “create_clump_hairs” node should transfer from the skin.

I'm using my own fur tree but I have just checked Fur out of the shelf and - YES this is exactly where I have inserted my new furdensity attribute … and that is why I was confused why overall density of fur is changing too..

screens: changed furdensity attribute just before FUR sop
and normal furdensity without clumping

Also clumpradius is primitive attribute and of course I need to transfer it in order to get it working, but I don't see a point here if I cannot use it locally (per point/vertex)



Another interesting thing is furclumping attribute:

here is standard fur without clumping:

and here is fur with clumps turned on BUT furclumping is set to 0 for all points:


why there is slight difference between fur without clumps and fur with clumps and furclumping set to 0 ? is it problem with standard CVEX (furstyle) ?

With Houdini 10.0, all hairs must be a member of a clump. Hairs too far from clump curves are culled. From the screenshots, it looks like hairs are being culled as the “clumpradius” value is too small for the behaviour you want. “clumpradius” is a primitive attribute as it is just used to determine which hairs may be associated with a clump.

Thanks Derrick for Your help, but I still have problems with this….

derrick
as the “clumpradius” value is too small for the behaviour you want.

ok, but I like my clump radius look in one spot and I do not need to have clumps on rest of my surface … so place without clumps shouldn't be changed at all.. meanwhile there is difference between places without clumps (0 value on furclumping attribute) and clumps totally turned off (not connected to fur sop / fur geometry shader)

For eg. In this case (file I have attached above), I had to set clump radius to value of 3 to get similar fur look to that one without clumping (and it's ok for places that I don't want to be clumped but for spots that I need to have clumped, value of 3 is way to big.


And what if I have to create fur for an animal that have clumps but very dense and with small clump radius on few spots and sparse fur clumps with big radius on the rest of its body?

I just need to have mixed values on one surface..

Think of an animal that is dirty (so it's fur is clumped in few spots) and it's also partially wet (so its fur is also clumped but with totally different clumping settings)

The only way out is to use multiple fur geometry shaders ?

bumping. Anyone got an idea for elegant way out ?

I think there is some confusion about how the “clumpradius” attribute is used. It is just a bound to limit searching for hairs that might be a member of a clump – a hint for optimisation. The Fur SOP can cook faster if this is a tight bound, but make it too tight and some hairs might be omitted. Neighbouring clump hairs are what really limit how big a clump appears – a higher density of clump hairs results in smaller clumps.

In Houdini 10.0, when clumping is enabled, all hairs must be members of a clump. This restriction will be removed in the next major release of Houdini. Until then, if you want a portion unclumped, you will have to make it part of a clump but ensure the behaviour of that clump is a no-op. For example, create clump curves even in unclumped areas but set “furclumping” to zero where there should be no clumping. If you don't wish to create clump hairs where there is no clumping, consider creating a single “unclumped” clump hair and set its (and only its) “clumpradius” to a value large enough to encompass the entire object.

tmdag
And what if I have to create fur for an animal that have clumps but very dense and with small clump radius on few spots and sparse fur clumps with big radius on the rest of its body?

As long as the “clumpradius” for each clump is large enough to encompass all hairs you want members of that clump it will work. Of course, if you can specify tighter bounds using per clump hair “clumpradius” values, your cook times will improve.

thank You for help so much!