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sds issue.
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sds issue. // Archive: Tech Forum
Post by rjeff // Nov 29, 2007, 11:13am
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rjeff
Total Posts: 1260
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Ok SDS is a thorn in my side. Here is two images..before sds and after. I divided all the faces in to qauds..or what I precieve as quads. Please look and help me out. I want to learn sds. |
Post by TomG // Nov 29, 2007, 11:21am
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TomG
Total Posts: 3397
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It looks like you have vertices in the middle of an edge in many places. Note that SDS pulls to these vertices, so they will affect the outcome of the shape - in effect, these are not really quads, since the one edge has been split into two with the vertex in the middle of it.
These are frequently called "floating" vertices - while anchored in one face as part of the edge, in the other face they are just sitting there.
These are what are causing the "pulled in" parts on the shape of the mesh. You should connect those vertices up to other vertices, so that every vertex is always part of edges and is not left sitting alone on an edge :)
Thanks!
Tom |
Post by rjeff // Nov 29, 2007, 11:25am
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rjeff
Total Posts: 1260
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Look at the image. |
Post by TomG // Nov 29, 2007, 11:27am
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TomG
Total Posts: 3397
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See attached image, where I have highlighted just a few of these vertices.
Note that these will also cause problems on export to certain formats.
HTH!
Tom
PS - one of your highlighted vertices is NOT floating, the one in the bottom left, it is fine. Basically a quad face has to have only four vertices along its edges. When you have five vertices, then the face has a "problem" (actually it is fine in many cases, but not good for SDS or exporting). |
Post by rjeff // Nov 29, 2007, 11:34am
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rjeff
Total Posts: 1260
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Ok so instead of attaching thoes to the edges I need to attach them to the vertices. Even if they look "not square". |
Post by rjeff // Nov 29, 2007, 11:36am
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rjeff
Total Posts: 1260
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Tom while you are at it can you check my post a ways down about paths. I think you can answer this one. |
Post by TomG // Nov 29, 2007, 11:37am
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TomG
Total Posts: 3397
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Two more images - one shows where there should be extra edges someplace (though just drawing these in will make more floating vertices where they intersect the opposite edge!).
Note that for SDS models it is best to always work in "loops" as much as you can, so that you shape the model along these loops. It's kind of an artform :)
The next image "counts" the vertices on some faces to show the problem another way.
Note that I may have got some of the faces wrong, hard to tell in a still image where you see backfaces :) But the idea should be there so you can check it in your model.
You could bring the model along to TNL! tonight and discuss it in the Caligari Clinic, we usually have some great modelers in there who could share tips on SDS and that sort of thing.
HTH!
Tom |
Post by TomG // Nov 29, 2007, 11:42am
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TomG
Total Posts: 3397
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Yes, doesnt matter if htey look square, so long as they have only four corners they'll be fine for SDS. You may have to just draw a loop all the way around the model (so draw an edge to the opposite edge as shown, and then repeat again to avoid having another "floating" vertex, then again, and so on, til you come up the other side of the model - since its symmetrical that will solve the problem on both sides when you come around, and will get you into a situation where you have complete loops to work with.)
As noted its kind of an art rather than a science, and the more you do it, the more you will be able to just "see" when something looks like a good SDS mesh, or "see" how to achieve what you want :)
Will have a look at the paths, though I did glance at it and didnt have an immediate answer to hand, not having done so much with paths :) I'll revisit it though!
Thanks!
Tom |
Post by rjeff // Nov 29, 2007, 11:53am
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rjeff
Total Posts: 1260
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Ok I will bring my model..casuse I have no idea what drawing loops means |
Post by Jack Edwards // Nov 29, 2007, 7:39pm
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Jack Edwards
Total Posts: 4062
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rjeff did you get the answer you needed?
I can post some examples tomorrow if you're still looking for help.... |
Post by Nez // Nov 30, 2007, 12:42am
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Nez
Total Posts: 1102
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NB - this is something Jack is really good at, so I'd take him up on it! Jack - it would be really good to see a few examples of good 'cages' for SDS, especially showing how to deal with things like corners (sharp and smooth) without getting vertices with more than 4 edges converging (think they're called 'poles'?) and how to get a square recess in a face...
With the 'poles' I realise that in some cases they don't even matter too much but they can look really bad and ruin the nice smooth surfaces
see my 'wrong way' examples below - I'd be glad (and expect rjeff would too!) to see how they ought to be done... pretty please...:o
I'm beginning to improve a bit at SDS but still have along way to go.... |
Post by TheWickedWitchOfTheWeb // Nov 30, 2007, 3:43am
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TheWickedWitchOfTheWeb
Total Posts: 858
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Straight edges/sharper corners are easy with SDS, once you know how!
The trick is to increase the mesh at the points where you want a sharper smoothing (that sounds so backwards but you know what I mean!).
Here's a quick 'n' dirty example using your test object and a couple of quick clicks with the 'add edge loops' tool to give you the idea. Obviously with a bit of additional tweaking the mesh can be refined further but this'll show you the basics of how it works.
9847 |
Post by rjeff // Nov 30, 2007, 4:18am
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rjeff
Total Posts: 1260
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Nez I did the same example as you did the the 6 blocks and I get this result. |
Post by Nez // Nov 30, 2007, 4:40am
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Nez
Total Posts: 1102
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I think you may have only 1 level of SDS applied - if you increase it to 2 levels you should get the result I did (I think). I'll check in a mo but TS is busy at the mo... |
Post by rjeff // Nov 30, 2007, 4:46am
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rjeff
Total Posts: 1260
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yeah that was it Nez..I applied another layer and it worked. |
Post by Nez // Nov 30, 2007, 6:23am
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Nez
Total Posts: 1102
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Phew, at least I got that right... even with 2 levels of SDS, it still won't look very good though, especially rendered...
Straight edges/sharper corners are easy with SDS, once you know how!
The trick is to increase the mesh at the points where you want a sharper smoothing (that sounds so backwards but you know what I mean!).
Here's a quick 'n' dirty example using your test object and a couple of quick clicks with the 'add edge loops' tool to give you the idea. Obviously with a bit of additional tweaking the mesh can be refined further but this'll show you the basics of how it works.
Thanks WWotW - that's a useful pic. Unless I'm missing it, TS5 doesn't have a nice add edge loop tool - I can manually add single edges, but that's pretty slow going. Still - slowly, slowly, I'll get there in the end... |
Post by Jack Edwards // Nov 30, 2007, 11:13am
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Jack Edwards
Total Posts: 4062
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Hi Nez,
WWotW has hit upon the key point, you need to think in terms of loops. Poles are mainly an issue when you don't want pinching during animation. For non animating objects it's not particularly an issue.
No object in real-life has an infinitely sharp edge like with 3D geometry, that's why 3D objects look fake. It's the rough and rounded edges in real world objects that catch the reflections that make highlights on the object. With that in mind, it makes more sense that what you need is more geometry around the edges to detail them.
In simplistic terms you can think of it as edges that are closer together make a tighter crease. I'll do up some examples and post them. |
Post by rjeff // Nov 30, 2007, 11:18am
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rjeff
Total Posts: 1260
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thanks..maybe you can explain the edge loops to me..cause I have no idea what thoes are. |
Post by TomG // Nov 30, 2007, 12:23pm
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TomG
Total Posts: 3397
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An edge loop is just as the name might imply - a loop of edges that go all the way around and come back to where they started. If you set off walking along one of the edges, you could go along that edge, onto the next and along it, and end up back to where you began.
You could think of these as like "elastic bands" wrapped around the object. They "hold in" the shape of the SDS object, maybe like an elastic band around a balloon (I sometimes think of an SDS object as being like something that inflates, until it "hits" the edges of the control cage that then constrain it at those points, and it fills up taking up a rounded shape constrainted by the cage it is in).
HTH!
Tom
EDIT - as a PS they dont always go around the object, they can just loop along the surface, eg around an eye socket, there are loops of edges that go all the way around the eye, when working with SDS to make a face. But I started out with the simpler example of going all the way around the object, as that is what would work in the case of the object you were showing :) |
Post by Jack Edwards // Nov 30, 2007, 12:54pm
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Jack Edwards
Total Posts: 4062
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Sorry about the delay. Here's 2 examples:
One with the basic shape:
9856
Another with tight loops around the edges that need to maintain their shape:
9857
I did use some triangles to reduce some of the detail loops (for the extruded areas) and so as not to create long narrow face loops along the flat surfaces. You want to try and keep your polygon distribution as even as possible, to maintain good loop flow.
9858
Others may have solved it differently but this seemed the simplest approach.
Thanks for covering edge loops Tom :) |
Post by rjeff // Dec 2, 2007, 2:14pm
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rjeff
Total Posts: 1260
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thanks for the advice. I need to experiment with thoes. |
Post by Jack Edwards // Dec 2, 2007, 5:39pm
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Jack Edwards
Total Posts: 4062
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You're welcome. :)
Catmull-Clark SDS (what TS uses) requires a bit of different thinking when modeling. The Doo-sabin model is a bit more intuitive, but I'm not aware of any 3D apps other than Mirai that use that and Mirai is sort of dead now...
Also if you're working in 7.5 you can use the edge weighting tools to create sharper edges without adding extra geometry. |
Post by Nez // Dec 3, 2007, 12:34am
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Nez
Total Posts: 1102
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Thanks for the examples Jack; I know I've still got a long way to go on this area... part of the 'fun' is having to build edge loops one edge at a time in TS5, no nice 'add loop' tool (that I'm aware of). I need to start collecting lots of nice sample images like these and putting them to one side as reference material for how to construct good meshes to apply SDS to... |
Post by TheWickedWitchOfTheWeb // Dec 3, 2007, 2:07am
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TheWickedWitchOfTheWeb
Total Posts: 858
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in TS5, no nice 'add loop' tool
Not native tools, no, but they are available via the amazing PolyTools plugin suite if you can find a copy. Adds many, many other invalueable functions too, certainly worth getting if you can. |
Post by Nez // Dec 3, 2007, 3:01am
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Nez
Total Posts: 1102
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Thanks for that - I've heard this plug-in mentioned a number of times but gather CK aren't about any more.
I did manage to find a copy of the TSX files (thanks to the archive TXS page set up by Emmanuel) but obviously can't get a registration code so am limited to 200 vertex objects which I expect is quite restrictive.
I'd assumed it only worked under TS6.6 but have just tried out a few of the tools on small objects and they appear to work so I guess I've got some fun tinkering ahead - just on small objeects only! :rolleyes: |
Post by rjeff // Dec 3, 2007, 4:13am
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rjeff
Total Posts: 1260
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Nez I have all thoes FX packs that came with TS5 when I bought it. What is the name of the software you want, I may have it on my cds'. |
Post by Nez // Dec 3, 2007, 4:23am
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Nez
Total Posts: 1102
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It's called PolyTools and is a collection of something like 17 plug-ins including 'knife', 'magnet' and a whole bunch of others - I believe some of these tools (or equivalents) may exist within TS7.5 but I think edge extrusion still isn't? (or maybe is, but in workspace only?)
The unregistered version only works on objects up to 200 polys. It could originally be bought from CK Gamefactory on line from whom a registration code could be obtained, but this site has closed down and I understand from other posts that it is pretty much impossible to get in touch with the author. If you have a code, you right click on the magnet plug-in to bring up a panel to enter the code...
I have the actual TSX files as they can still be found online, but no registration code :(
Cheers though for the thought. |
Post by rjeff // Dec 3, 2007, 6:01pm
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rjeff
Total Posts: 1260
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Jack I am really going to ask the stupid questions here, because I am so very ignorant about sds. I tried to find the "edge loop" tool but I can't seem to find it. I went though the TS manual and could not find this tool as well. Is it even a tool? |
Post by Jack Edwards // Dec 3, 2007, 6:35pm
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Jack Edwards
Total Posts: 4062
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My fault, it's called "Add loop". It's a tool new to 7.x. You'll find that there are times where it won't make the loop you need though when modeling for SDS. In that case it's sometimes easer to highlight the faces hold the control key and do a group extrude, or just draw the loop using the polydraw tool.
Also if you find you are getting an odd SDS result, rectangle select over the problem vertex and use the weld tool. Sometimes there are two vertices very close together that are causing the problem. |
Post by rjeff // Dec 4, 2007, 4:11am
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rjeff
Total Posts: 1260
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Thanks again Jack, but I still can't find anything with the "add loop" name or similar. I have done a search in the icon finder and nothing. Sorry for bothering you, but I just can't find it. |
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