What's causing these artefacts when rendering my baked normal maps? I'm trying to bake normal maps for my first hi poly to lo poly sculpt and things are coming out wonky. 

I made the low poly mesh by remeshing it in Instant Remesh, and then decimating it further using a Decimate Mod in Blender. It's not pretty topology but it was a fast way to do things and I've seen similar things done online etc, and I just plan on using this as a static character sculpt. 

The normal maps are coming out looking weird once I apply them to the Lo Poly model. 

Here's some pictures:





Also I have a thread on Blender Artists I started asking for help that also includes a blend file for download. 

https://blenderartists.org/forum/showthread.php?435940-Baking-normal-maps-for-the-first-time-and-things-are-looking-funky-on-the-lo-poly-out
I'm pretty sure that weird artifacts on your bake were caused by the bad topology of low poly mesh. I 've made a really quick and dirty retopology of the model (it's still, like your previous low poly model, around 50 000 verts). I 've also really quickly unwrapped that mesh and baked the texture.

Here are the results and as you can see there are still some artifacts around UV seams. I'm sure you can do it better than I did if you invest some time in making a good mesh and a UV map.



the normal map bake:





Look in the .BLEND file for more information. I removed the high poly model from it because of the size but you already have it, so I guess that isn't a problem.