I made a little guy and rigged his legs with an Armature modifier. I've done the weight painting manually. However, when I attempt to move his leg, it doesn't follow the armature like it should. Any fix?
It's your weight painting. Every single one of your bones has too much influence over the mesh. Luckily, there is an easy solution.
First, select the mesh and delete the Armature Deform object modifier. Next, RMB select the mesh, then Shift + RMB select the armature (make sure both are in Object Mode) and key Ctrl + P to open the parenting menu. Select With Automatic Weights under Armature Deform (pictured below). It may take a while to parent because of the high vertex count. Afterward, your mesh should now have reassigned weights and move perfectly.
The Parenting Menu.
I do not have media fire, so I could not include a .blend file. If you have any question, though, ask away.
The use of a Decimate modifier set to Planar and Angle Limit: 6.4 can solve the Bone Heat Weighting Failed issue. Read more about in my answer here. Download a rigged and finished .blend file below.
Your mesh have too many unrelated bone influences. Your best bet at this point:
- Get into weight painting mode
- Select all the bones
Assign Automatic from Bones.
If you do make any adjustments, make sure the brush is set to 'Add' and make the power 1.0. The lion's share of weight-painting can be done this way.
Slightly unrelated: the model has way too much geometry for the detail that it has, and you can likely half, even quarter the amount of faces you have without losing any meaningful features. This will ease up on your filesize, and viewport performance. You should also give your bones meaningful names (Femur.R, not Bone.004).