Photo alignment

I've posted on this subject before, and the situation hasn't improved.

Years and years ago I remember seeing a demonstration of some cad/rendering package where you could pick a series of points on a photo of a building, then pick corresponding points in the model and the program oriented and zoomed the camera to match.

Ok, so SketchUp doesn't have this tool. Nothing's perfect.

But trying to eyeball it is an exasperating experience. Everything moves and there are too many variables.

Can anyone with a good skills in perspective geometry and explaining things to dummies describe a workable solution that tells me

a) how big to make the imported photo

b) how far from the model to put it

c) what factor on the zoom (I assumed to match the camera's lense, but that doesn't seem to be working)

d) where to place the camera.

Ideally, this solution could be 'modeled' with lines in the drawing!

KWG

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Kevin,

I'm a big fan of the "2 & 3 point perspective matching" method detailed by Michael Young. Some have suggested that it's easier to "fudge it", but I think that if you follow the tutorial and try it for yourself, you'll be convinced.

2 & 3 point perspecitve matching

Now for your list:

a) Pick your leading edge. make it as big or bigger than in real life (don't magnify errors by doing it small, then enlarging).

b)Covered in tutorial.

c)trial and error. You could try using bakbek's camera_parameters.rb [camera_parameters.rb or camera_parameter_fr.rb or from the Ruby Library Depot] and to match the Horiz. FOV (SU uses a Vert. FOV by default).

d)Covered in tutorial.

It is possible to automate this process in a ruby script, but it goes beyond my knowledge (I'm still playing with display modes - I'm not into geometry, yet).

-wehby

Thanks. I haven't worked through the full tutorial but it looks good. Picking that leading edge is the trick, though. That enabled me to get close enough that I could use the skew and distort transformations in photoshop to complete the effect.

KWG