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Curving a perforated sheet


Johnm

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I would like to be able to draw a perforated sheet of metal bent to a curve of my choice (perforations as say on the face of a mac G 5 tower).

I want to end up with a perforated solid object to test the effect of light passing through .

I'd be pleased to hear how do you go about achieving this.

Jonas Mac

G5 dual, OSX10.3 VW&RW 10.5

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I did as propstuff suggested and found replies to a similar question by Geoffrey P 03-21-04 which I need to digest as I am not too well up on mask transparency etc.

Thanks also for the other replies.

I would like to progress to taking a thicker sheet say a half inch thick standard sheet of ply with

holes drilled at regular intervals and then bent to a curve , how would you model this in VW /RW.

Jonas Mac

G5 dual 2 OS 10.3 VW/RW 10.5

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The problem is that for what you require you have to perforate the sheet in its curved state and to do this correctly you need to have each hole running parallel to the curved centre of the sheet.

It's possible but involves a huge amount of work from what I can see.

I've tried perforated sheet using two methods, clip surface then extrude and by subtract soilds method.

Both slowed my computer to a crawl, tieing it up for great lengths of time as the calculations for each hole was worked out.

I even tried it in stages but the more holes I added the slower the computer ran.

This was on flat sheet. I imagine curved sheet would increase the computations considerably.

Good luck

Alan

[ 08-22-2005, 07:56 PM: Message edited by: alanmac ]

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I have modeled this in the past as Alan has and with the same methods, and had the same result. A file that groaned with the calculations. That's why I used a mask transparency.

In short, it's do-able, but slow: you'd want to have a fast computer and a specific reason for doing it.

BTW, (as far as I know), you cant make a solid and deform it like that in VW. Concepts Unlimited can, but I don't know if it would work with a perforated solid.

good luck.

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One more method... the Fractal Approach:

Create a Fractal NURBS Surface symbol of the minimum case which in this instance is a single hole penetration into a slightly curved slice the thickness of the plywood. Then iterate that Fractal symbol to form a composite of the entire surface. It's quick...it's easy ... and it renders relatively fast. Also, of course, it's far simpler to make changes to the single Fractal Symbol...

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Sure... a Fractal is the simplest possible shape that best represents the required data. In this case a curve surface of certain thickness with an extruded hole punched through it.

The Fractal then is the minimum NURBS solid with the extraction of the tapered extruded circlular hole.

To keep it simple I just used a 10? arc with radii of 5 & 4.75 and width & depth of 1 to create the NURBS solid for the plywood then I extracted out the 10? tapered cylinder of r=.25 & .2375 and depth = .25. I applied the standard Pine texture to the solid.

In the image above the arrow points to the Fractal just described.

Then I converted it to a symbol with a 3D Loci at 000. Once the Fractal symbol is set to the center of the GP it is possible to iterate it by duplicate array to create 90 similar stacked solids with holes in them. Rendering time depends only on a single Fractal symbol...so it's instantaneous.

Here's a link to the original file for you to check out:

Example_CurvedPerforation_VW11_file

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The trouble is that perforated sheet does not exactly come like this example.

Each row is alternated to have its hole centres offset by 50% of the row above or below it.

Guess you could still do it this way but would need to create a shape with a hole in the centre and a quarter circle at each corner, so when duplicated these become complete holes.

Wonder how that would work on render times ?

Alan

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quote:

Originally posted by islandmon:

Just offset the Fractals row by row. And then create a solid 1/2 to fill in the end conditions. End of story...

Not quite end of story EJ but that is very good, easy way of thinking.

Better if the solid half had half a hole in it to be really accurate and done easily as the other ones you created I'm sure.

Must try this method when I've got some time.

Well done.

Alan

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Islandmon,

OK it's time to write the book. Sometimes your answers are at once both painfullly cryptic and intellectually enticing. I am often responding with "so how do I do this" or "how can I learn that?".

Produce the esoteric knowledge and they will come. You could title it, "Nurbs and Other CAD Geometry: a Practical Guide in Plain English with step-by-step Instructions for the Average CADmon". I, for one, would buy it.

Perhaps there are already some books out there you could refer us to?

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bc... mucho gracias for your encouraging comments. FYI for the last 5 years I've been writing and publishing a compilation of the basics of Synergetic Geometry and the Isotropic Vector Matrix including stereo imagery to help explain the concepts.

But alas, the project is running too far ahead of the time I have to give to it these days.

Thought you might enjoy checking out a Quantum Gravity module. This little sucker exists in a portion of our Universe where a transcendental like pi is simply not required.

Here's the link to the 2.5mb Quicktime VRML if you're interested...

Quantum Gravity

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