draw a controlable hand with OpenGL?

OpenGL OpenGL: Advanced Coding
1

I did draw a virtual hand with glutCylinder and cube.But it seems not so realistic. Once I wanted to load the 3D hand from CAD modeling directly, but its a bit hard to control all the joint parts flexibly. Any one
could help me? My PC also installed OpenInventor, which completely support VRML files. Thanks for your any kind help.

beet

2

glHi,

I was thinking about doing something like that in SGI Performer, but I’m short on time. I was thinking about the same thing, taking a VRML model. If you always want to have a closed surface you will have to put spheres in the joint area.
Further to have controll over all joints you have to setup a model hierarchy which should look like that.

palm
+thumb
I~+1. phalanx
I~~~+2. phalanx
+forefinger
I~+1. phalanx
I~~~+2. phalanx
I~~~~~+3. phalanx
+middle finger
I~+1. phalanx
I~~~+2. phalanx
I~~~~~+3. phalanx
+ring finger
I~+1. phalanx
I~~~+2. phalanx
I~~~~~+3. phalanx
+pinkie
~~+1. phalanx

~~~~~~+3. phalanx

If you have this hierarchy you will be able to move the palm down and the fingers will also move. if you bend your pinkie, it will remain straight until you move the 2. phalanx.

Hope this is somehow clearer to you, if not drop me a line to my mail adress.

glGreets,

Martin
3

Look up “bones” “skinning” “weighting”
in google.
What you want to do is something like this:-

  1. Load vrml mesh of a nice hand model.
  2. Load vrml model with lines representing bones in the hand.
  3. Determine how close a particular vertex is to each bone to find ‘weights’ (crude method).

You should apply your transforms (hiearchical rotations) to the bones model, and then calculate, using the vertex weights, how much to move each vertex in the fancy hand mesh.

You’ll effectively have a smooth skin over the bones in the hand.

You can do this in hardware using something like a geforce3 and OpenGL extensions - although I haven’t tackled this area, I’ve always done it in software with simple meshes.

[This message has been edited by knackered (edited 03-27-2002).]

4

thanks for your information, but Knackered you meant that I could found some VRML models for hand from internet? Do you know where could find theses stuff. I donot know very much about mesh indeed, could you tell me where the start point is? Not very much follow your post yet, thought it’s very useful.
Thank you and mphanke

I wanted to make some model with Unigraphics, but its a bit hard to access the joint control points for hand movement.

beet

5

glHi,

try http:\www.3dcafe.com. They have a section with free models. The other thing is to search for “3d models free VRML” on www.teoma.org and on www.google.com. For me teoma works better. www.gamedev.net has also links to free models. There are alot of pages concerning free VRML models on the net.

glGreets,

Martin

[This message has been edited by mphanke (edited 03-28-2002).]