Where would I start if I would like to have a spider animation that I can put over a video of a person sleeping and have the spider crawl out of their mouth.
I tried looking into Blender but that seems more for 3D models and less about animations.
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Sign up to join this communityNo, Blender does animation as well. Here's an example of a spider animated with it:
However rigging and animating a realistic octopod is not exactly the kind of project you'd start with as a newbie. There's a lot to learn.
But if you want to have a go, you could start with this tutorial on rigging a spider's leg in Blender: https://www.blendernation.com/2011/03/16/how-to-rig-a-spider-leg-in-blender-2-5-tutorial/