I modeled a turtle, the legs are short. Ok so when i try to rig a leg with a bone by parenting the bone to the leg and using automatic weights, it moves other vertices all over the mesh. I have it weight pained right, only the leg is painted to move.
So why is it moving lone vertices all over the mesh when i try to rotate the leg?
Difficult to say when we have to guess what your model, rig and weighting looks like.
You should always supply an example blend file that shows the problem so anyone who decides they may want to help you has all the info that you do. You can upload blend files to http://www.pasteall.org/blend/, just reply with the download link
http://www.pasteall.org/blend/31639
There. Also, most times my weight paint brush doesn’t work so its hard to even paint the model. I have to keep switching the blending modes and brush size for it to work. wtf?
Could this be moved to the rigging section. I didn’t see it before.
The mesh had a few problems.
In edit mode, select all vertices then execute Remove Doubles and Recalculate Normals.
When using parent with Auto Weights, its best to have some more bones, the other leg bones and some body bones for example, or else the auto algorithm will just assign all vertices to the one bone.
In the file you posted, some vertices were weighted just a bit to the leg bone, because they were not weighted to any other bones the influence was 100%.
You can remove all the weight easy by using the tools in the Properties > Data > Vertex Groups panel, while in edit mode.
In weight paint mode, the brush blend was on Multiply, set to Mix for a more normal affect.
Heres a modified version of the file: http://www.pasteall.org/blend/31653