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# 3D Arcs?

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Hi, Can anyone help me with drawing a 3D arc (a bent cylinder)? Is there a library providing such function? Thanks!

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Why no try extruding a cricle along a 2D curve? You store all the points in the curve in an array and center a circle around each point joining up the poinst to make polygons (quads would be easiest).

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Is this reliable?
I mean, that is a huge number of polygons just to draw one arc.

what do you think?

Thanks

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It might take a while.
But it should work for you.

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Are you talking about a 3d line or a 3d curved surface?

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A 3d curved surface, a 3d line is actually a cylinder!

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hmm.. i have code for a dome that could be modified to function as an arc. ill work on it, then post the code lol

Thanks!

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quote:
Original post by FreakyMisfit
A 3d curved surface, a 3d line is actually a cylinder!

A line can move though a 3d area, I was wondering if you were looking a line that curves though 3d space.

As for a curved surface it''s not too hard to create a function that will draw it, where params can be size, detail(how many segments make up the surface), etc.

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oh, so ur talking about an arc, i was thinging something else.

the dome code wouldnt be as easy to modify as i thought then...

my suggestion would be to go to math.com and look up sin and cos. these will be very valuable to u and everyone must know how to use them. it would be better if u try to ficure out those, becuase with them, u can just create a loop for ur vertex arrays lol... im still modifying the dome code though lol

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Hi skow,
You really think it''s not too hard to write such function??

umm .. will you do it for me?!

I was trying to avoid writing it the entire time, maybe finding a library providing it!

Thanks skow and relpats_eht!

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No I won't write it for you as that would be counter productive...But I'll try and point you in the right direction

The easy way of doing this would be to model it in a 3d program and load the model.

If you wish to do it manually...

Think about how you would have a function draw a cylinder... Say its specified as a radius, how many segments around the y axis, and how many points along the z axis...

Now using these inputs instead of just raising them strait up you want to curve them. I would recoment either doing 1/2 a tourus or fitting them to a sin curve, depending on the look you want...

If you wish to do this yourself, and need more help I can explain a little more how to do this at a later time.

[edited by - skow on April 24, 2004 2:02:55 PM]

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Hi skow,
obviously you didn''t catch that this was a joke (the smiley!),
but Thanks for your help ...
But maybe you could help me with NURBS curves, I never used ''em, What''s the difference between the control points and the knots?

Thanks everyone!

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Ohh, my bad, there are so many people who come here asking people to do their code for them I kinda always assume its not a joke.

As for the NURBS curves, I''ve never used them much in OGL, so I cant be of much help. The very little I did use of them I learned from http://www.mat.ucsb.edu/~c.ramakr/articles/dls/nurbs.pdf

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Thanks skow!
I guess that''s all

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