Adding body to a Fetus

Hi there,

I have done a face of an ultrasound file but my issue is I would like to close the head of the image. I tried the paint function but for some reason it does not want to work.

If I can close the head in a semi good way, export it as STL and then edit that image to look presentable then I’ll be happy but I cannot add anything to the image.

Is there something I am doing wrong?