Splines and 5-point patches

[swooster]

I was wondering what is considered good spline and patch design in A:M. So far I'm up to exercise 11, and it seems like TAOA:M always has 2 splines running through each control point - as a result, 3-point and 5-point patches are necessary. I have an acquaintance who is very experienced at modeling, and he claims 5-point patches are a bad habit and should be avoided; according to him, models should be made entirely out of quads to prevent creasing. However, he works with LightWave, so I don't know how applicable that advice is to A:M.

 

Here's an example of a foot he modeled: (copyright oDDity)

Although it's made entirely out of quads, that seems to necessitate occasionally having an odd number of splines meeting at a control point. Is that ok to do in A:M or is it generally frowned upon? Also, is it ok to have more than 2 splines passing through a control-point? Thanks!

[martin]

That there is a VERY bad example of modeling in A:M. How could a spline possibly know how to terminate into a junction like that? Only polygonal modeling techniques that jury-rig the normals, or shrink the surface with subdivision could possibly work in the case exhibited. And there is no accounting for animation of the toes. Does that terminated line simply stretch? Never use polygon examples as a way to model in A:M.

[frosteternal]

I was wondering what is considered good spline and patch design in A:M. So far I'm up to exercise 11, and it seems like TAOA:M always has 2 splines running through each control point - as a result, 3-point and 5-point patches are necessary. I have an acquaintance who is very experienced at modeling, and he claims 5-point patches are a bad habit and should be avoided; according to him, models should be made entirely out of quads to prevent creasing. However, he works with LightWave, so I don't know how applicable that advice is to A:M.

 

Here's an example of a foot he modeled: (copyright oDDity)

Although it's made entirely out of quads, that seems to necessitate occasionally having an odd number of splines meeting at a control point. Is that ok to do in A:M or is it generally frowned upon? Also, is it ok to have more than 2 splines passing through a control-point? Thanks!

 

5 point patches are not a "bad habit" but can be a very handy tool to use, when needed. If the foot WAS modeled from Hash patches as pictured (which it is not, those look like subd surfaces) it would crease on the toenails, and also the ridge where the foot connects to the toes. The splines would be "dead-ending" on each of those little arches (which might be okay for a foot, but most likely not).

5 pointers come in handy most often, in my experience, in hands (connecting fingers) toes (connecting toes) and the cheeks of a face.

 

Look around the forum and study the spline layout of some other models, or check out the ones on the cd. Spline layout is an art, and can't effectively be studied by looking at other modeling methods for examples.

[swooster]

Thanks for the info! I probably should have clarified that the foot wasn't modeled using Hash patches, but it's helpful to learn that Hash patch modeling is different from subdivision modeling.

 

I do have one more question... On page 128 of TAOA:M, it says:

Avoid attaching hooks to a spline that makes up a 5-point patch! Or multiple 5-point patches next to each other!

But the Giraffe exercise has you create two adjacent 5-point patches and there don't seem to be problems... How many adjacent 5-point patches is it ok to create? (I tried creating a long strip of 5-point patches, which seemed to work ok) Or does it depend more on the geometry than the number of adjacent 5-point patches?

[frosteternal]

Thanks for the info! I probably should have clarified that the foot wasn't modeled using Hash patches, but it's helpful to learn that hash Patch modeling is different from subdivision modeling.

 

I do have one more question... On page 128 of TAOA:M, it says to "Avoid attaching hooks to a spline that makes up a 5-point patch! Or multiple 5-point patches next to each other!" But the Giraffe exercise has you create two adjacent 5-point patches and there don't seem to be problems... How many adjacent 5-point patches is it ok to create? Or does it depend more on the geometry than the number of adjacent 5-point patches?

Yeah subd's are totally different - best to not even think that way. I haven't found any other modelling paradigms that really are at all similar to hash patches. This is a good thing!

As far as adjacent 5-pointers...it does depend greatly on the geometry. 5-pointers are best used in areas where the surrounding geometry provides plenty of curve detail. 5-pointers extrapolate their shape based on surrounding shapes, so while in one case two of them adjacent might not cause trouble, another case it might. I usually try to separate them by one quad (standard) patch, but have successfully joined two at a common edge. Just do plenty of test renders, certain shading options (like porcelain, which averages normals) are trickier to use with 5-pointers. Just remember, if it looks right (and animates properly), it IS, in most cases, right.

Oh, and to answer one of your earlier questions about intersecting splines...you should not have 3 or more splines ending at any given point, it will crease. Caveat : this may be desirable sometimes. Not usually.