View Full Version : Sub-d hard edges

06-23-2003, 02:27 PM
I found a way to get hard edges without breaking the surface. I had noticed that LW had the ability to create polygons that are not normal. They are 4 sided polygons with only 2 points. At first I could not figure out how to reproduce them. Well I figured out today and this is what you can do with it.


Don't get to excited it's not a perfect salution. For rendering you need to hide the edge polys or freeze your mesh and delete the extra edges. Here is an object for you to expore to see how it's done. All you do it make a 4 sided poly weld two oposite points them weld the ends. then weld them into the edges you need hard

edge object steps (http://www.steelronin.com/temp/edging.lwo)

I'm guessing someone could make a script to do this.

06-23-2003, 03:10 PM
You can get the same effect pretty easily by increasing the subpatch weight where you want a sharp edge on a sub-d. Switch to weight map view, hit the airbrush, n and select subpatch from the drop-down menu. Move your cursor over one or more points and watch your object bleed orange and straighten out...

06-23-2003, 03:20 PM
I don't want this to turn into an argue about edge weighting. Go do that with 4 points and come back. There is no question that edge weighting can be helpfull for sub-d modeling even if it only Takes alittle bit of work to get the simaler results. This is a workaround for hard edge wieghting for modeler that really need it right now.

06-24-2003, 06:38 AM

You can't use subpatch weights for this object, and here's why:


Picture 1 is the un-subD object.

Picture 2 is the object with sub-Ds turned on.

Picture 3 uses subpatch weights on the top and bottom points, notice how the top and bottom are square.

Picture 4 uses Castius' technique, notice how the top and bottom are round.

With how many people have been asking for edge weighting, I'm surprised that this thread hasn't been a little bit more active than this.

06-24-2003, 06:58 AM
Originally posted by meatycheesyboy
With how many people have been asking for edge weighting, I'm surprised that this thread hasn't been a little bit more active than this. We don't want probably another cumbersome "Tips & Tricks" technique but a full implementation of "edge weighting"! ;)

After all... many compliments to Castius... you deserve it! :)


06-24-2003, 10:03 AM
Thanks Exper

Maybe next time I will post in Tips & Tricks. I was thinking a 4 sided poly with 2 points was somthing better put here cause I myself don't exaclly know all that might be posible with this yet.

In case anyone would like to fallow the cgtalk thread.

06-25-2003, 11:35 AM
Oh, I see what you demonstrate now, Castius. The 2-point poly trick can do things mere weight increases can't. I usually freeze sub-d models for rendering anyway, unless the model is a character.

When I need a hard edge on a sub-d without freezing, I just smooth-shift part of a surface, without extending it, once or twice.


06-25-2003, 12:48 PM
Same here -FP-.

06-25-2003, 04:44 PM
Sometimes I just do a bandsaw at like .99%.

jin choung
06-25-2003, 11:26 PM
of course just slicing a thin row of polys next to the edge you want to sharpen will create a crease.

but the point is that it's a godda#4n stupid, inelegant way of doing it in this day and age.

we have vertex weighting that's just this side of useless but the principle is correct - we need to be able to sculpt and detail using weighting information.

but we need more than just vertex weighting. we need edge. we may perhaps desire even face weighting.

and all of these are on display in the latest incarnation of c4d.

we've been harping about this for a looooooooooooong time now. i shudder to think how many threads feature this exact request.

which is why this thread hasn't been more active. we've said it. we've uttered it. a thousand times and again. if they haven't heard by now, they never will. god, if i were them, i'd freakin' give it to us just be done with the subject.

this issue, along with the inability to accurately uv map sds surfaces (although jack daniels came up with a brilliant work around) keeps sds being the 'robust as polys' geometric type that we've been longing for. it's just not done yet.

but the thing with weird polys creating a sharp edge is an interesting solution.... though too bad it does not provide a means of GRADING the sharpness of that edge.


p.s. have you tried just using 2-pt polys? create 2 verts, select, hit 'p'. then do the same thing. it might provide the same effect in one less step.

06-26-2003, 03:27 AM
what was the jack daniels work around?

06-26-2003, 10:08 AM
This is NOT a request Thread. This tread is about how to create 4 sided 2 point polys and what can be done with them.

06-26-2003, 04:39 PM
How can you have a 4 sided Polygon with only 2 Points? It's physically impossible.

jin choung
06-26-2003, 05:58 PM
jack's brilliant workaround:


i don't think it's two verts. it's four verts but two of them are coincident.


06-26-2003, 07:20 PM
Thanks for the link Jin.

I checked out the object, the technique does create an object with 2 Points and 4 Vertices.

It looks like a 2 Point Poly line but doesn't behave the same.

Very odd will have to think about this one for awhile.

06-26-2003, 10:14 PM
Pretty funky isn't it

By the way these polys can be created without you knowing. best way tp find them if you ue the statistic window and check your non planer polys. Under info it say the flatness is degenerated on these polys.

06-26-2003, 10:49 PM
Yeah I was wonderring about that, if this could cause problems like pinching etc. Will have to check it out. Thanks for the tip.