Hi

I want to select polygons ( primitives) base on picture, i mean base on a mask


I created a mask of object which I can select in houdini exact polygon that I

Want ?

Sorry for my english, hope I can say what I mean.

Tnx

hey Farrokh, try this:

- use an attribute from map SOP node to bring in your mask as the color (Cd) attribute

- use an attribute promote to convert your color from points to primitives (source attribute, points, destination attribute, primitives)

- drop a group SOP, and under the number tab, choose the “by expression” in the drop down. Set this expression:

$CR > 0.5 (that picks any primitive with a color that is higher than 0.5 in the red channel)

- name your group on the top whatever you want

- use that group in any operation

hope this helps!

Thank youuuuuuuuu )

I will try ….

@grayOlorin


I have done what you said but …..

In fact ) i have modeled a face in zbrush then i want to bring in houdini to work on eyebrow and eylashes with add fur, so i polypaint in zbrush the form of eyebrow that i want and make alpha from that, now i want select the polygon of eyebrow in houdini, i have done what you said but i do not know what to do with fur in houdini, to define that….


Sorryyyyy & thaaaaaaankkkss )

hey Farrokh, there are several options here:

- if you are using polygroups from zbrush, you may already have groups in houdini when you import the mesh as an obj file. To see this, middle mouse in your file SOP and in the info pop up, see if you have any primitive groups already coming in frmo zbrush

- I have not yet used the houdini fur operator, but most operators have a group field (at the very top), which you can use to limit the effect of the operator to just that group (or groups)

- likewise, a lot of operators in Houdini you can also drive with attributes such as color (or maybe some density attribute on the mesh). you you may be able to use the mask to drive the density falloff of your fur object

- I would maybe look at some fur documentation to see if you can use groups or attributes to drive the density of the fur

hope this helps!