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Author Topic: Determining 3D angles from 2D pictures (homography?)  (Read 2931 times)
eventhorizon5
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« on: July 03, 2006, 06:33:25 am »

In my project that uses CS (at http://www.tliquest.net/skyscraper), I'm trying to accurately create a model of a fictitious building in 3D (the Glass Tower) but only have 2D picture references to go by, taken at different angles.  I know that you can calculate the angles of things such as walls by using line intersections (usually from vanishing points and such) and perspective matrices.  I'm mainly trying to calculate a view of the building looking straight down from directly above the center (in order to have an outline of the perimeter walls) because some of the wall angles that me and others have come up with seem to be incorrect, but I just can't figure out how the stuff works.

Here's one picture that I rotated and marked up (the angles I'm trying to find are marked with the partial circles):
(original is here http://www.tliquest.net/skyscraper/1.1/glass_tower/temp/full2.jpg)



Current top-down drawing (originally drawn by someone else; I modified it and added coordinates):


Our angles that seem to be off (after simulating it - pics are on the website) are the 2 angles I marked, which are for the top right triangular setback wall (the one that angles inward), and the bottom left wall (seems to be angled inward more, instead of almost straight).  Here's a small pic of the simulated model (more pics are on the website):


So if anyone could help me figure out how to calculate this stuff, that would be great.

-eventhorizon
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