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| Using CSG to calculate displacement volume [message #60633 is a reply to message #60632] |
Wed, 19 August 2009 10:30   |
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Wayne Parham
Messages: 18726
Registered: January 2001
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Illuminati (33rd Degree) |
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You can calculate displacement volume using a CSG estimate. CSG is constructive solid geometry and it's a term I borrowed from computer graphics that describes what I'm talking about. As an aside, I was a contributor in the POV-Ray ray tracing project, providing the support for the Inmos line of multi-processors. That's where my ray-tracing terminology comes from, but I was actually using this same process long before ever calling it "CSG" - There is a program called "volume.exe" in the original PiAlign distribution archive, and it was written in the 1970's. I used it as a simple calculator, allowing me to estimate volume offsets using a CSG approach.
Using a combination of primitive shapes (cylinder, wedge, cone, etc.), describe the parts inside the box. For example, a brace is a simple box so that one is easy - just calculate its volume using HxWxD. Write that down. To calculate a loudspeaker, simplify its shape as a cylinder (the magnet) and a cone (the basket and cone assembly). The formula to calculate the volume of the magnet (cylinder) is πR2H and the formula for the cone is πR2H/3. Simply make some measurements of your parts and calculate the volume offsets. You can go to whatever level of detal you want when estimating shapes, for example, you can use a single cylinder to estimate the magnet or if it has a bulge in the center, maybe you'll calculate as three cylinders. A horn may make be modeled as a wedge or a pyramid or a cone, or perhaps as a combination of several primitive shapes.
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