After dithering about for far too long I finally started on modelling with camera projection. I found a nice simple subject, used fspy (great program, that) to match the camera, scaled up a cube to fit and used Project from View to texture.
I’ve had a few issues with sfpy in the past, when it was called blam, but either it has improved or my understanding of how to use it has improved (probably the latter) and getting this result was pretty straight forward.
I’ve had a few focal length issues in the past, especially. My cameras use a crop sensor, but the lenses are generally rated (focal length) for a full frame camera. I noticed with this image that fspy identified the lens as 31mm (the stated focal length) but Blender gave the camera as about 48mm focal length, which takes into account the approx 1.5x magnification factor of the crop sensor. I guess what mattered is that the cube, when scaled up appropriately, fitted the reference image perfectly.
The scene needs a lot more work to complete, but I was really just getting the workflow sorted here, as usual. I wonder if I’ll ever put in the work required to finish something properly.
The background here is the HDRI I used to light the scene, not the original photo containing the building.
After much exploration (and frustration) I managed to transfer the texture from a projected view to a regular unwrap. Easier to edit I think. I’ve removed a car bottom right, not very well. I need to use BI to do the cloning. I wonder if anyone on BA will tell me how to do it with nodes.