Edge Cusp And Facet

[lanchka]

What do the edge cusp and facet sops do?

Could someone give me a practical example?

Any help would be appreciated

Cheers

Lanchka

[aracid]

What do the edge cusp and facet sops do?

Could someone give me a practical example?

Any help would be appreciated

Cheers

Lanchka

17671[/snapback]

hey Lanchka

it basically assigns unique points to each poly and not have poly's share points, thus allowing u to adjust the normals on the poly, therefor u can have the hardening or faceted appearence of poly faces.

take a look at the point count on ur geometry before and after the edge or facet sop(u have to either tick unique points or cusp poly), u'll see the res a difference in the number of points.

it looks like cusp poly in the facet sop does the same as a a edgecusp sop, thats if u adjust the cusp angle in the facet sop.

the cusp angle is the threshold at which the sop actually breaks up the poly into individual polys.

as for a practical example,

when i recieve geometry from maya, and the faces render abnormally, to fix this i pass the geom through a facet sop and tick post compute normals and unique points, it seems to correct the problem.

or Take a poly sphere and compare the render with and without the above mentioned sops. u'll notice it creates a more faceted look to the sphere.

i assume that when geom shares points it blends the poly normals between the point's normals it shares, giving u the appearance of a softer surface or rounded normals, and having the unique points or cusping the geom, hardens the polys appearance because each poly has its own group of points with .

anyways, hope this helps

aracid

[lanchka]

Thanks a lot.

So if I wanted to get sharp edges on certain parts of a character , could I use edge cusp (with a suitable cusp angle), before I actually subdivide in real time, on those edges or edge loops that have to look creased

(or instead the facet sop in a way somewhat similar to assigning smoothing groups before smoothing in max)

Thanks for your reply

Really thankful to this community

Cheers

Lanchka

[stu]

If you're using renderman you could also render as a subdivision surface and apply a suitable crease weight (crease SOP) to those edges that you would like to be sharp. Keep in mind that the crease SOP has no affect if you're using mantra.

If you're using mantra and would like a semi-hard edge, try the polybevel SOP (with polys, of course).

stu

[edward]

Well, if you have crease weights, the subdivide sop will also use them.

[stu]

Of course the downside to using the subdivide SOP in this case is the uneeded increased point count on flat surfaces.