Help with Rigging Robot Characters legs

Question

Im relatively new to blender and rigging and I'm trying to pose a model but when I am moving the legs (Thighs and Shins) the legs deform to account for the position on the shin and makes the mesh of the model bend when my character is a robot made of metal and should not be able to move like that. I have tried to follow along with other post to no success, if anybody would be willing to look at the model for me or be able to guide me through how to do it myself it would be greatly appreciated -CE

Link to the Model https://drive.google.com/file/d/19skyk1ReAXNoNhuREYS70_0W9RbWoewH/view?usp=sharing

Answer 1

For an object like a robot, don't parent With Automatic Weights, which is made for organic objects, it will bend your mesh because the vertices may be assigned to 2 vertex groups or more, and therefore may be deformed by several bones.

Instead you can use the Parent > With Empty Groups mode for example. It will create as many vertex groups as you have bones, but your vertices won't be assigned to any of these vertex groups for the moment, you'll do it yourself:

Apply the Mirror modifier, select the vertices you want (use L to select each limb faster), for example thigh.L (except your leg is only one mesh instead of two, maybe you should correct that), go into the Object Data panel > Vertex Groups, select the vertex group to which these vertices are supposed to be part of, and click on the Assign button: