I'm trying to create an interior based on an anime. Problem is that no matter how I set up FSpy it gives me a focal length of several hundred millimeters. If I wanted to match the image my models would have to strech to around twice their size in the y direction and if I lower the focal length things don't line up. Since this is not a photo is it likely that this is an impossible angle/shot?
I've got the same problem, and This is how to solve it: - Once you set all axes correctly, you fill find a red point - Change that red point position, make it closer as much as possible to the vanishing point (intersection of the 2 axes) - Then save it and it will work correclty
There a couple of things to remember 1/ the principal point - because your picture has 1-point perspective it’s a very simple case - the principal point should overlap the vanishing point
2/ it’s very difficult to determine the focal length in fSpy because it doesn’t provide precise tools for this; however as soon as you have the vanishing points (one point in your case) and the principal point properly set you can import the file to blender and find the proper focal length there. The process isn’t automated - it’s rather guessing, matching and retrying through eyeballing. I’m your case I’d use a circle for this and try to match it against the lamp/mirror in the upper left part of the image
I cover this and other cases in my fSpy tutorial which explains all fSpy options
Maybe it can help: https://youtu.be/daiMOYR8GS8