Thursday, January 30, 2014

How'd He Do That?

A number of folks have asked about the rendering I did of the proposed antenna farm at the new SEOC.  I'm not an artist, I can't draw worth a darn.  The images were produced using constructive solid geometry - that is, the images are the result of a bunch of equations.

The way this works is simple, at least in principle.  You write a bunch of expressions describing a bunch of objects, and the computer figures out what it will look like.  Skilled artists can make breathtaking images, but for a tecchie like me, it can be very helpful to try to visualize something.

The first time I realized this was back in the 90's, and it really hit home when Chip Cohen, (then NI1R) began talking about his patented fractal quad yagi (FQY) antenna.  His claims were fantastic, but people just couldn't understand it.  Try as he might to explain it,  he kept getting accused of trying to hide what he was actually doing.

I made a tracing for myself to try to understand it, and sent some images to Chip, which he used in an article in Monitoring Times.  That led the magazine to commission me to do their cover artwork, which remains my only published artwork.  These images are all created with POV-Ray, a rather old, open-source program, but one capable of amazing results.

While creating a scene like this was can be tedious, it really isn't all that hard.  In the antenna case, I began by modeling an aluminum tube, 1 inch in diameter and 12 inches long, by writing

 cylinder { <0,0,0>,<0,1,0>,1/24 texture {Aluminum} }.

(I used units of feet, so a 1" diameter tube has a radius of 1/24 of a foot).

I then arranged four of these in a square

One foot of tower

and put quarter inch tubes diagonally across each edge.

This gave me one foot of tower.  OK, perhaps it will be a triangular tower, it probably will be a little different size, in fact, we haven't specified the tower as it has to comply with FEMA standards.  It probably won't be your typical ham tower.

5 feet

I had towers of 20, 30, 35 and 125 feet, so I combined the one-foot sections into five-foot sections, which I could then combine into the appropriate heights.

The sky is a standard "texture", and while I probably could have used a more aesthetic sky, the first one I tried looked OK so I just stuck with it.

  sky_sphere { S_Cloud1 }

The General Office Building (GOB) is in the background and mostly obscured, so I simply modeled that as boxes.

  #declare GOB1 = object { box { <-95,0,0>,<95,35,2*95>  texture { Brick } } }
  #declare GOB2 = object { box { <-34.34,0,0><34.34,50,148> texture { Brick } } }
  object { GOB1 translate <-39,0,333> }
  object { GOB2 translate <-39-34.34,0,422> }


I had intended to get fancy with the "Brick" texture, but I ended up with simply a light brick colored pigment, and for the GOB, probably quite a bit different than reality.

One wall
For the SEOC itself, since many of the walls are at odd angles, each wall was modeled as a box, and rotated into position.  Since the measurements were taken off a relatively small drawing, the odds are they aren't very accurate, but they can at least give a feel.  I again used the "Brick" texture because I have no idea what sort of texture will be used on the new building.

Finally, oversized cylinders were used for the wires.  Modeling drooping wires is possible, but a pain in the neck, and copper colored wires of a realistic size would be invisible, especially in the movie, so I used 1.2" diameter black cylinders.

Adding a few trees (from an example macro that produces pretty ugly trees), a little fog to make some things appear a little less prominent, and we have something that can give us a feel for the antenna farm.  I have to admit to being terminally lazy, and even though someone else did the hard work of figuring out how to model a tree, I wasn't about to write a line for every tree.  So, I wrote a C program to generate code for 800 trees in four rows, two on each side, of randomly varying heights and distances.

For the movie, 99 frames were made of the same scene, moving the camera between each frame.  The individual frames were combined with ImageMagick.

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