Old Rusty Tank

inspirationWhat a great tank! I found this on M82a2’s Photobucket page. I wanted to see what I could do with it as it would make a great mini-scene .. rusting quietly away in the scrub.

I will be using Sketchup’s Match Photo to make an attempt to bring the photo to 3D life. The basics are that you import a photo into Sketchup as “as New Matched Photo”. You are given two pairs of Perspective bars with ‘handles’ on either end. You drag the bars by the handles until they align to the photo. This works to .. an extent. If the photo has been cropped that can cause problems since the software ‘assumes’ the the center of the photograph was dead center of the camera lens when the photo was taken. The other problem is that all lenses have artificats .. pincushioning for example. What we have to do is get close. With a little luck .. and a little skill .. and knowledge .. we can build a model from this.

Match Photo Setup
MatchPhoto_1The dashed green lines on the end of the tank are the Y-Axis Perspective Bars. The little squares on the ends the ‘handles’ used to align the bars. The top bar was alined to the top rungs of the ladder and the bottom bar aligned along the timbers. On the right we have the red X-Axis Perspective Bars. I aligned these along the walk supports and along the bottom of the long beam. The blue vertical line is called the “origin” .. and this is as the name suggest, where all lines originate. What this does is calibrate Sketchup’s camera to the position and focal length of the camera used to take the photo.
Match Photo Drawing
MatchPhoto_traced_1The next part is to draw out from the orign point. The hardest part was the take itself .. the trick there is to group the tank so you can move it around and adjust the diameter until it matches the photo. Once that is done you can simply pull the tank out to it’s full length. I’m not worried at this time about the scale of the tank .. I will figure that out later. Those LOOK like railroad ties so I can “guess-ta-mate” that they are 9″ wide.
SURender.. and this is the result. Not an exact copy .. as I said earlier, the software can only do so much based on the photograph used. It re-creates the position of the camera that took the photo with the assumption that the center of the photo was also the center of the scene as seen by the camera. If the photo has been cropped this is no longer true. The other problem is that a lens may distort in variious was .. Barrel, Fisheye and Pincushioning can all change the photo. That’s why we have to create an approximation of our subject –

I moved the hold-down strapping so it is on either side of the dome .. but all in all I think it came out pretty good.

Orthographic Projection
orthoThis is the end result, the ability to create an Orthographic Projection. A top, front and end view. I only put a few dimensions on the plan just for the ‘heck of it’ .. tank length and diameter, overall height, timber size etc.

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