here is an exported texture from poly paint of an arm, obviously I didnt paint it this way but when I hit “texture/new from poly paint” this is what I get…
the rest of the model maps/textures correctly from poly paint… whats causing this blocky result, it happens on both arms so Im guessing since they were mirrored in the low poly, that makes since… but I dont know what is causing this…I thought at first it was flipped normals in the low poly but that doesnt seem to be the case…
Looks like it might be a normals issues or an issue with the UV mapping. It could also be an applied material issue, two different but similar materials assigned to different faces. Might even be a layering problem. Are you using layers and/or different materials on your model?
looks like your UVs are too close to your border IMO
You can check the UV Map in ZBrush by going to ‘Tool > Texture Map > Create’ and clicking ‘New From UV Check’. If there is any red in the resulting texture map, then ZBrush doesn’t like your UV’s. A usual cause of this is as beta_channel suggested. If any of the UV islands are touching the border of the UV space then problems occur. Move the islands in from the edge or scale them down a bit.