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Bones
About Truespace Archives
These pages are a copy of the official truespace forums prior to their removal somewhere around 2011.
They are retained here for archive purposes only.
Post by 8-bit // Oct 12, 2008, 1:10am
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8-bit
Total Posts: 84
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Im still learning about bones and have a question. In the image below I would like to produce a joint half way down so that it bends much like a elbow up and down. Can this be done to the shape on the right, as its just one long polygon, or does it have to be made of several polygons like the one on the left?
http://i4.photobucket.com/albums/y112/blazer-glory/Example.jpg |
Post by RichLevy // Oct 12, 2008, 1:43am
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RichLevy
Total Posts: 1140
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In order for the mesh to deform/move it needs to have the geometry to do it, even the mesh on the left would be ackward. If you group a couple of edge loops in the area you want to deform you will be far better off.
Rich |
Post by TomG // Oct 12, 2008, 4:30am
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TomG
Total Posts: 3397
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Bones can indeed only bend existing geometry - they can't make one solid section bend in the middle, as there are no vertices for the bones to control and move.
So you would indeed need to go with the one on the left - although you could have some more edge loops closer to the joint as mentioned if you want a smoother bend there.
HTH!
Tom |
Post by 8-bit // Oct 12, 2008, 12:17pm
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8-bit
Total Posts: 84
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Thanks for the replies.
Im not actually going to use the objects featured I'm just trying to understand the concept of bones and using them. I'm still a little baffled as to how to use them and how they work ;) |
Post by RichLevy // Oct 12, 2008, 12:40pm
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RichLevy
Total Posts: 1140
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An easy way to look at it... you arm if it did not have a joint at the elbow, that it was a solid bone, would not be able to bend... the converse, if you did not have any bone at all, the flesh would not be able to support itself, it would just fall to the ground in a heap. You would have to lean to move from a pile of organs, skin and muscle with out the structure of a bone system to support you. The joints allow your bones to have movement. I think TomG did some really nice videos on the basics of TS bones (from the WS side), you can find them i the manual in the character animation section. There are also videos that work with the manual and they will provide you even more information to work from.
HTH
Rich |
Post by 8-bit // Oct 12, 2008, 12:41pm
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8-bit
Total Posts: 84
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Thanks I'll check them out :)
BTW what manual version do you mean? I have version 6 |
Post by TomG // Oct 16, 2008, 7:01am
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TomG
Total Posts: 3397
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The videos are in the tS7 manual (since they relate to the tS7 workspace bones). They are an optional download, due to the file size, so be sure to download them along with the PDF part of the manual.
HTH!
Tom |
Post by 8-bit // Oct 16, 2008, 8:11am
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8-bit
Total Posts: 84
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Thanks. Where can I download them from? |
Post by TomG // Oct 16, 2008, 8:42am
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TomG
Total Posts: 3397
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Info should be in the email you received on registration I believe, or even as links on the page after you register. You can go to repeat downloads here, that should work post-registration if you didn't grab all the goodies at first :)
https://cart1.caligari.com/ebuy2/enterdownloads.asp
HTH!
Tom |
Post by 8-bit // Oct 17, 2008, 1:09am
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8-bit
Total Posts: 84
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many thanks.
One more thing. What are the point of bones if you can create joints without them? |
Post by TomG // Oct 17, 2008, 5:06am
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TomG
Total Posts: 3397
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I am not sure what you mean about creating joints without them?
Bones are a way to deform a shape, which would otherwise be impossible to do. Imagine having to select all the vertices for an arm in point edit mode, then rotate and move them in space, to make it so that the arm is bending or moving. It would be impossible, but not with bones.
The only joint you can make without bones is the old way of doing things, which is making the arm a separate object, gluing things as a hierarchy, and then you can animate parts of the hierarchy by rotating those parts. This however gives no bending of the surfaces so only works for either mechanical shapes, or for not realistic effects for organics.
So you really can't make joints without bones, at least not realistic organic ones. And that is the point of them :)
What has been described here is that you need the geometry in the mesh for the bones to be able to bend the mesh. Bones work by assigning vertices to themselves, and then the assigned vertices move with the bones. Without enough vertices to assign to the bones, the mesh simply cannot bend. So you need to add vertices at the right places to get the bending - but without the bones you would be manually selecting vertices and moving them about and it would be impossible.
So the bones don't remove the need to model vertices in the mesh, they exist instead to control those vertices in the mesh. So you still need to "model the joints" in the sense of adding enough vertices there for the bones to control to give the desired effect :)
HTH!
Tom |
Post by 8-bit // Oct 17, 2008, 5:12am
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8-bit
Total Posts: 84
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I was just following the example in the TS6 manual on page 451 called "Tutorial 3 : Building a Finger Object with Joints"
In it 3 cylinders are joined and moved simply by adding 2D joints between them. |
Post by TomG // Oct 17, 2008, 5:39am
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TomG
Total Posts: 3397
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Yes, and there is no real bending in that case. If you look at the results, you will see the join between one cylinder and the next, and it does not look like a real finger, because there is no smooth bending of the skin at the joint, instead there what is obviously one cylinder going inside another.
This is fine for a robot finger, that may be built that way. Fine for pistons and other things that do not flex or bend. But not fine for a human finger, which bends at the joint, the skin stretching or compressing, without any join in different pieces of geometry. To achieve that realistic effect of a single skin that bends, stretches, twists and deforms, you use skeletons and bones. Something that can't be done by gluing shapes together and animating each separately as in that chapter :)
HTH!
Tom |
Post by TomG // Oct 17, 2008, 5:49am
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TomG
Total Posts: 3397
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See attached, with a very hastily built set of objects. Note the ugly visible seams between cylinders on the left, and the smooth bending of the object on the right. The finger on the right could use more geometry still for better bending and flexing of the skin, but it shows the difference.
Note that on the workspace side (which is the new technology and is the recommended place to do most of your work - absolutely don't use bones on the Model side, they are not very good!) there is no concept of the old joints between geometric objects, like in the chapter you were describing.
So its using separate geometry and animating via hierarchical groups for mechanical, rigid, inflexible objects, and using one piece of geometry with bones and skeletons for flexible, organic, bending objects.
HTH!
Tom |
Post by 8-bit // Oct 17, 2008, 6:21am
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8-bit
Total Posts: 84
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Many thanks.
I was trying to clarify whether you could produce a moving joint without bones, while I think you misunderstood me as how best to do it. :)
I can see now by adding bones to one solid mesh gives far better results than by using separate polygons 'joined' its just you was one step ahead of me as I was just practising the basic use of them using the tutorial. :) |
Post by TomG // Oct 17, 2008, 7:06am
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TomG
Total Posts: 3397
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It's a big and complex area, with a lot of questions to be asked and answered! Sorry if I misunderstood what you were asking, but I'm happy if the information proved useful anyway :)
Keep on asking questions, as it's the best way to learn, combining that with reading tutorials and following videos, and you'll get the hang of it quick!
Thanks,
Tom |
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