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Double Helix


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Hi, I am tryin to build the double helix DNA moel in VW and am having trouble attaching the spheres to the helix path. I have tried 3d spheres and 2d circles trying to construct in 2d then create the helix with the corles or spheres on it. I have now run out of ideas. is this possible in VW using the attatch to path tool or any other device.

Thank you

David

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David, you'd have to say that 3D snapping in VW is not ideal, but there are a couple of key points:

Double click the Object Snap in the constraints pallette and tick the Snap to Edge Points.

Second, make sure when you are moving the spheres that you do it with the 3D selection tool. The 2D selection tool sees everything as being a flat shape "on the screen" and will say it's found the object/ point but will not actually see it in 3D.

Another option would be to make 1 sphere, then successively do Cmd D to duplicate, then use Modify>Move>Move3D to move to the next position in 3D space.

BTW, where is the "attach to Path tool" you refer to?? I don't recall ever having seen it.

Are you out there Islandmon?: you should have some ideas for us on this?............

HTH

N.

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Hi

thanks for the reply. I gave up in the end and constructed a extrude along the path to produce an extruded tube of the right diameter,then painfully positioned by eye and going through the complete series of views to position each sphere using the tube in wireframe as the guide. This is only a visual so the accuracy is not defininative, however i need to do different size proportions of height ad diameter for a visual choice for client. Its going to be a long day ! Anyone out there with more ideas will be welcome to us both . The "Duplicate along path tool" is in the tool pallette behind the mirror tool box. It seems to be a very twitchy tool and does not like seeing a helix. Perhaps there is a basic reason for this ,ie type of object

Thanks

David

Edited by TWICKENHAMAN
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Hi

The "Duplicate along path tool" is in the tool pallette behind the mirror tool box. It seems to be a very twitchy tool and does not like seeing a helix. Perhaps there is a basic reason for this ,ie type of object

Thanks

David

The Duplicate along Path tool (I thought that's what you might have meant) does have some problems, but it is not intended to work in 3D. Like the 2D Selection tool, it only sees the flat screen, not "the space behind it".

I seem to recall the DNA consists of Arms of AGC -and... the other one, groups which are arranged in the spiral. Is that right?

I would make each of the groups as a symbol (although that might mean 4X4X4X4 different symbols???)

and snap - or Move 3D, those to the helix.

If you're still having trouble with the snapping, you could make a helix of 3D Loci by the Move3D method, group the loci and rotate a duplicate of the group to produce the double helix. You should be able to easily snap to the loci in 3D space.

N.

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Hi

thank you for the replies. In fact my DNA helix is very simple compared to this.It is merely the two helix spirals interlaced to each other in the usual way BUT it has just spheres attached to the main helix axis. All the spheres ( balls) are nudged up tight to one another.

I dont really understand the use of loci so any breif explanation would be useful. in the meantime its out with the manual and turn to page ... and read up on loci. ( if thats the right thing to do? )

Thanks

David

Edited by TWICKENHAMAN
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Loci are (non printing) "markers" which can be snapped to, so if you make a helix of loci you will have all the points to snap to.

If your spheres have to touch but not intersect, I would make a little "constellation" of 3D loci the correct distance apart so that the spheres are the correct distance apart, and make a Symbol of it(them?). Then arrange the symbols in the helical array.

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Hi Nichcolas,

I have made the string of ten loci the correct distance apart and have formed the correct helix from a line ( line tool) and tools "create helix spiral" . I made a symbol of the loci and attempted to attach the symbol of loci to the helix. Sadly the loci string remains as a straight line and does not attach to the helix spiral. There is no intereaction between the two. I have also tried selecting the loci by themselves and requesting "make helix spiral" but to no avail. There seems to be NO path content to the spiral in both cases.. What am I doing wrong please.

By the way thanks for your time in this as I am learning something new here.

David

Edited by TWICKENHAMAN
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Duplicate array needs to have an elevate function included in it so that you can do a circular array of an object like a stair tread and have each successive copy raised by a required distance. This would then make modelling the DNA fairly straightforward (I hope) by combining a sweep with pitch and a circular array of a repeated symbol.

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