View Full Version : Sub-d hard edges

06 June 2003, 09:15 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 (

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

06 June 2003, 10:47 PM
Maybe I get something wrong, but you can use weightmaps (SubPatch Weight) for hard edges ! :shrug:

There was also some free plugin somewhere !

06 June 2003, 11:00 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 June 2003, 11:10 PM
I'd say that adjusting the sub-d weight map is a much easier and quicker method than this :shrug:

06 June 2003, 11:14 PM
Ok no argue, but what you think about

bandsaw with a Value (.005 or 0.995).

Pretty hard edge too :D

06 June 2003, 11:28 PM
ok maybe I didn't describe this well enough. I know there are other ways to do this. I only wanted to show something probable 99.99% of the users didn't know about. That you can have a 4 sided polygon with only 2 points.
This could help user that do allot of hard sub-d edges cause they wouldn't have to worry about welding points together that are really closeby accidently. This also have much less poly count if you choose the freeze method of rendering.

06 June 2003, 12:41 AM
Sub-D weighting wont work for this Leigh.
In the example that Castius posted, if you tried that with Sub-D weights the top would have come out square rather than round.

I can't think where I would use this (usually go with an extra cut), but it's handy to know.
Thanks mate. :thumbsup:

06 June 2003, 02:56 AM
A neat trick, I always used bandsaw for the extra geomitry to sharpen up an angle.

06 June 2003, 04:02 AM
"And where does the newborn go from here. The Net is vast and infinite."

We will have to see where else this can be usefull.

06 June 2003, 04:29 AM
that seems exactly like what i would like to do on a car model i'm working on....bandsawing makes nice edges but then you have to deal with the row of polys all the way down the model (ie crisping a corner seam but then having it change the shape of the smooth door surface). I downloaded the example file but I didn't exactly get what you meant heh, I guess I'll have to mess around with it more...

06 June 2003, 05:28 AM
you can do the same sort of thing a lot of the time if you copy and paste the faces where you want the hard edge... in you example you could just cut and paste the 4 faces around the lip and you'd get the same result... then you can just freeze the object to merge it all back into one


06 June 2003, 05:52 AM
I challenge someone to try and reproduce this with weights!

Nice idea, Castius!

06 June 2003, 05:59 AM
You can achive the same result using Smooth Shift.

06 June 2003, 08:33 AM
althogh i can't understand his think.
but here, a man said is right: Cut &Paste
then get a hard edge, between 2 part of polygons.

06 June 2003, 01:24 PM
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.

Awesome technique Castius', Thanks.


06 June 2003, 01:27 PM
Also, I forgot to make a picture but copying and pasting the polys, doesn't come up with an object that's even close to what is shown above.

06 June 2003, 04:08 PM
Copying an paste the polys is another trick as well but you can't exactly call it a hard edge. It's a hard poly. and here is what that would look like.

you will notice it's not the same.

and you could never do this.

You however can do this with Extender and achieve the exact same thing. It even has some advantages. You don't need to hide anything. Plus you are able to weight one of two points that are in the same spot. That can be a little funky but it's possible. But can be deleted with welding. I wouldn't want to uv and keep track of that.

06 June 2003, 04:33 PM
I also think Motion designer see the polys so it might be somthing that could be usefull in that area. I don't know MD that well though so I can't say for sure.

06 June 2003, 04:48 PM
Here's what I meant

06 June 2003, 05:12 PM
Thanks riki for showing in more detail.
I showed the copy paste mentioned. I should have also showed the smooth shift method. My explanation for the differences in these methods still applies.

I really was just excited about figuring out how to reproduce the odd polys. I should have started this post completely different. Next time Iíll much more clearer to avoid miscommunication.

06 June 2003, 07:39 PM
Castius, I'm not exactly sure what you did to get the first example you just posted but here a quick pic of how cutting and pasting looks... (maybe you copied and pasted over the original faces?)

first pic is obviously the regular subd object. The second one I selected the red faces and then cut/pasted them. The third one I selected in faces inside the shape and cut/pasted them.

of course this won't work for everything but it dose work sometimes if you want a really hard edge.


06 June 2003, 07:57 PM
It's all in the details.
You said copy and paste before. And I said this was done without breaking the surface. Once again you have to worry about welding.
I'm going to have to rename this tread "hard edges.. A million and one ways" :)

got to love how many ways you can do things in lw.

06 June 2003, 08:03 PM
Originally posted by Castius
I should have started this post completely different. Next time Iíll much more clearer to avoid miscommunication.

Oh Castius, I understand it the first time too, the results looks alright, if you really want absolutely hard edges !!!

Iím a round edge guy, OK I admit that really sounds stupid, :banghead: but I really hate hard edges, there is nothing in the real world with hard edges so I will use my bandsaw 99.999 % method !!!
And every time I got these four point polygons, you know these edge polygons you like, I delete them, because in my opinion these polygons are troublemaker. :curious:

Sure if there would be a script like your mentioned maybe it would be nicer, but hiding these edge polys and freezing your model, I donít think thatís a to great workflow.
Just my 0.02 % of the Ä.:shrug:

06 June 2003, 08:33 PM
robinson, I couldn't agree more. I was only offering an alternative. If one person gets use out of it and helps than it was worth it.

06 June 2003, 09:32 PM
Originally posted by Leigh
I'd say that adjusting the sub-d weight map is a much easier and quicker method than this :shrug:

The problem with sub-d weight maps is that it affects both directions of the curve, as opposed to just one. If you could get the vertical edge straight and make the horizontal edge smooth, that'd be an ideal situation.

06 June 2003, 09:34 PM
I'm still not getting how you make a 4-point polygon with only two points. *tired*

*Edit* I figured it out.

Create a single 4-sided polygon. Vertex 1 is Upper left, Vertex 2 is upper right, Vertex 3 is lower right and Vertex 4 is lower left. (Clockwise.)

Merge Vertex 2 to Vertex 4.

Merge Vertex 3 to vertex 1.

Then you've got it. Strange.

06 June 2003, 05:00 AM
How is what Riki posted different than bandsawing the crap out of the object?

I thought the main reason for the original post was a way to sharpen the edge without a buttload of polys on the ends.

06 June 2003, 05:07 AM
How many Polys can you fit in a butt???

:eek: :scream: :surprised

06 June 2003, 05:27 AM
I think it depends on the user, no matter what the number, it is always too many. :)

06 June 2003, 08:53 AM
hmm nice a new way.
but, u get 100% hard edges. I can't see any use for it, no object (U can find on this planet) has completely hard edges.

LW needs Edge Weighting ;)

@riki: your smooth shift way.
IMHO the use of bandsaw is faster than smooth shifting the polys.

06 June 2003, 03:10 PM
Well, this novice learned something from these multiple techniques.

I was trying to get similar results with the knife tool but it wasn't working for me. Now I've got some more experimenting to do :)

thanks folks

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