How/when to use SubD?

Wonderland

I keep hearing about SubD and recently saw someone post that if a character is not HD, change the SubD to 2... What exactly does that do and when should you use SubD? What exactly is it? Thanks.

Richard Haseltine

I think what you saw was advice to set the SubD level higher if there was a HD morph applied, not if there wasn't. SubD(ivision) divides the polygons of the base mesh (the "cage") into four polygons per level (so 16 for SubD level 2, 64 for level 3 and so on) - that at least smooths out the shape, and since it is applied after posing (and morphing) it helps to improve the look of the figure. 3Delight takes the SubD to the limit, but the preview and Iray don't - the preview uses the level set for SubD level, as do things like Octane and LuxRender that work with an exported mesh; Iray uses the Render SubD level. An HD morph is able to move the vertices that define the extra SubD polygons, unlike a standard morph which is limited to the vertices of the cage, so the viewport or render levels may not be enough to show all the detail - to see more of the morph in the viewport you need to increase SubD level, and you may need to incerase the render SubD level to get the full effect in Iray (most HD morphs use level 3, there may be a few that use 4 but very little if anything beyond that).

In iray SubD also determines the amount of detail available for displacement - there is a surface setting to provide extra levels but it is, apparently, inefficient so it is still better to adjust the parameter under Mesh resolution on the figure.

Wonderland

I only use Iray so if I want a character to be more HD or to use an HD morph, I need to change the SubD on both the character and in render settings? Or do the HD morphs already come that way?

What about hair? Often the hair comes out zig zaggy, (especially if I conform rather than parent), should I change the SubD on that or use smoothing...?

What is the difference between smoothing and SubD?

Is SubD only used on characters or also on props or scene items? Is it only for DUF files or cr2, pp2 or hr2?

When would I specifically use it?

Sorry, still so confused... I've noticed that many people on this site come from somewhat techie backgrounds, unfortunately I'm not one of them...

Richard Haseltine

Smoothing rearranges thee xisting mesh, SubD actually adds more divisions - so yes, converting a jagged hair to SubD may help, but you may need to adjust the Edge Interpolation setting if you find the edges of the hair vanish.

HD moprhs will usually warn if the Render SubD level needs to be increased.

Anything can be converted to SubD - you'd try it if the mesh was showing its structure in your renders (most often seeing the straight edges of the polygons that make a curved surface in the profile).

Wonderland

Ok, thanks, I think I got it. I REALLY wish there was a comprehensive manual with screenshots...