Help with fSpy

Support Modeling
#1

Hi!
I want to make a model building from a photo. I use fSpy for this.
But I can’t do it right. I tried different settings.

Photo of the building:

1914 Staats-Zeitung Building, William & Spruce Streets
1914 Staats-Zeitung Building, William & Spruce Streets1839×2300 1.15 MB

Option 1:
I set the X and Y axis. Principal point: Image midpoint
The Z axis is does not correspond to the corner of the building.

fSpy 1
fSpy 11920×1019 306 KB

Mesh in Blender:

bl 1
bl 11920×1024 337 KB

Option 2:
Principal point: From 3rd vanishing point. Set all 3 axes.
In Fspy, everything looks right:

fSpy 2
fSpy 21920×1019 289 KB

In the blender, the photo is shifted to the side and the mesh looks bad:

bl 2
bl 21920×1016 311 KB

Option 3:
Set the X and Y axis. Principal point: manual.
I moved the Principal point so that the z axis is at the corner of the building:

fSpy 3
fSpy 31920×1016 295 KB

In the blender, the photo is again shifted and the mesh looks bad. :frowning:

bl 3
bl 31920×1020 333 KB

I ask for your help.

#2

I can think of 2 reasons why it is happening.

  1. walls of the builidng are not perfectly paralell to each other.
  2. the photo was made with lenses that distorts the perspective. (mosts camera do that) Lines are not perfectly straight but slightly bended.

Maybe both

fSpy most probably works properly and the fault is in the building or the photo.

#3

As you say, likely the photo, I’ve tried several photos and the results don’t line up. Even when I have the known dimensions of a room, simply because the photo has either been tweaked in Pshop, or used a correcting lens.