[Newbie question] How do I make this mesh into a solid?

[mmanciop]

Hi all,

I started yesterday to meddle with CAD in general, and FreeCAD 0.19 specifically, and want to make a model to 3D print adding some toy-like capabilities to the [1] model. Right now I am at a stage in which, after Googling and watching tutorials, successfully importing the mesh in [1] and turning it into a shape (after much computation that made me doubt whether it was actually working), I would like to turn the T-Rex model into a solid to be able to do boolean operations on it. Right now turning the T-Rex into a solid is not working with

Cannot convert t-rex-solid because Shape is not a shell.

From my rudimentary understanding, I assume it is because of the hole inside the mouth of the T-Rex. If that is the indeed the reason, I assume I would be able to fix it by adding some part inside the T-Rex head to be a sort of "wall", so that its body becomes a closed void that can be filled. But I would appreciate tips from more experienced users

[1] https://cults3d.com/en/3d-model/game/t-rex-teckword

[drmacro]

Yes the mesh has to be manifold to start.

In Mesh workbench you can use the analyze and repair tool to fix minor issues.

Sometimes tools other than FreeCAD, such as Meshmixer, may be needed.

Once the mesh is valid, it is recommeded that it be decimated to under 100,000 tiles (see Mesh workbench Decimate).

Then Part convert to shape, then Part convert to soild.

In general, for organics like a t-rex, unless you want add a peg, or hook, etc (mechanical things) FreeCAD is not a sculpting tool (like Blender).

[Kunda1]

So in summary:
Mesh_Evaluation
Mesh_Decimating
Part_ShapeFromMesh
Part_MakeSolid