animation deform

Hello, im really new in blender so this might be a really newbie question. I made a character, added the bones and joined them with the mesh but when i move a leg the other one tends to follow it. please help.
here are some pictures for a better understanding thanks.

This is a problem of weight, as in “Weight Painting”. The weight corresponding to the bones of one legs goes beyond what it should and includes vertices from the opposite leg.

Easy fix: Edit your mesh and go to the Object Data tab (the blue triangle), you’ll find the Vertex Groups panel.

Step 1: Select all vertices. Select one vertex group matching a leg bone. (The name of the groups match the bones.)

Step 2: Click “Deselect”. You should see vertices deselected on the wrong leg.

Step 3: Select those vertices which shouldn’t be influenced by the bone. Click “Remove”.

Go to Step 1 until you have done all the bones of the legs.

Note that it’s normal for the weight of a bone to extend beyond its ends as long as it’s still on the same limb and/or on the same side of the body. Just don’t remove too much! :wink:

If you have weights from one side of the body crossing the center line to influence the other, that’s almost always due to unapplied scales and/or rotations. Make sure before parenting with automatic weights that you apply these. Ctrl-A in object mode. Should save you a bit of manual tinkering, though Kaluura’s method is correct if manual tinkering is still necessary.