I saw a tutorial on using a Photoshop tool that removed lens distortion from photographs so they’d make better background references. I thought I’d try something similar with the Gimp.
I started with some free reference photos from Got3D.com
The character I call Ellen is their Woman 4.
Gimp doesn’t have a lens distortion removal tool (that I’m aware of) but I did find Filters>>Distorts>>Curve Bend which lets you set up a curve to apply distortion to the image. I used this to undo the distortion added by the photographic lens to get what I hope is an orthographic image.
The filter only works on one axis, so I had to distort the top and bottom edge, then rotate the layer 90 degrees to distort the sides, then rotate it back. I tried to give the distorted image the same aspect ratio as the original, but Curve Bend doesn’t allow numeric input, so I just got as close as I could by eyeballing it. Curve bend does allow you to mirror one curve guide to the other, which is handy, and it will automatically add a layer if you tell it to work on a copy.
After I distorted the front and side views, I rotated them slightly to get them lined up (front view vertically, side view to match the head tilt of the front view.) Then I deleted all the layers except the two (front and side view) doubly distorted layers, doubled the canvas width, and set the two images side by side. I flattened the image so I could save it as a Jpeg, and then cropped it in Irfanview. (I could have cropped it in Gimp, but for some reason I find Irfanview’s crop function more convenient.)
Here’s a mesh produced using the adjusted reference photo.
Seems to me to be a bit narrow. Looks like Ellen has a wider face. Taking another look at the reference photo, she seems to be turned a tiny bit to the left, so the left side of her face is a bit thinner than the right side in the photo. Since I worked from that side and mirrored the wider side, the whole head is too narrow. I suppose after I realize the mirror modifier I can scale the whole head in x to match the girl in the picture.
Here’s Ellen with the changes mentioned above, a lot of tweaking especially the nose, and a simple skin texture.