So I've been trying to create this mesh for a while, and the rigging is the only problem I've had so far. I'm trying to rig just the head of a dragon, and I keep getting the same error message over and over when applying the automatic weights "Bone heat weighting: Failed to find a solution for one or more bones". I have tried all the fixes for this I've seen, such as decimating and subdividing the mesh, making sure the mesh is symmetrical across the x axis, making sure the origin for the bones and the mesh is at the center of the mesh geometry. Is there anything else here I should try? If you would like to try for yourself, I can email the file to you should you be interested. Any insights and help is greatly appreciated!
You could try this [30 char filler]
The mesh should be manifold (no doubles, no internal geometry, no holes, no spare parts, no intersections between geometries) to be sure the automatic weighting goes OK.
You can break your model into different objects to understand where lies the problem.
Apply rotation and scale, and modifiers.
Sometimes temporarily adding a subsurf modifier to the mesh helps the algorithm.
If not, use manual weighting or upload the file for help.