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For my drawing, I chose an impossible stairs image.
I used the nearest step as my reference plane, calling it a square
with side length = 1. I chose the next step up as my reference
height, with z = 0.2.
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These are the lines and polygons that I used to cut out the steps. The matrix
for polygon 16, the one joining the back-left staircase to the front-left,
is uninvertible. This polygon could not exist in the position where it lies.
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Most of the textures came out looking like this one, just a simple stair top.
Some were distorted for perspective, but they mostly looked exactly as you'd
expect.
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I had hoped that the program would be able to figure out what was going on, that
the loop was not closed and that it only looks that way due to the viewing angle.
Ideally, the VRML model would show the gap when rotated away from the angle at
which the loop looks closed. Instead, the modeler put the textures from the
staircase that closes the loop very far away from the camera, and distorted the
textures connecting these steps to the others very badly. This is one of the
distorted textures.
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This is a screen shot of the VRML model. Notice that the stair case that closes
the loop appears relatively intact, but far in the distance. This is a valid
interpretation of the closed loop. I was mostly curious about how the modeler would
handle an impossible image, and I was happy with the results.
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I decided to try a simple model of a desk for my image 3d model. This is a
picture of the desk in the oval office.
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This is the model that I defined in the modeler program. I defined the top
as its own texture to try to show how it protrudes over the rest of the desk.
I defined the base of the desk with a sweep rectangle.
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These are a couple of the desk textures, the one I defined for the top
and the front of the sweep rectangle.
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And a shot of the 3d desk. Notice that the top does protrude beyond the
sweep rectangle as expected.
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