How is this done?

[EricChadwick]

Poly by poly looks like to me. Extruding edges probably. He knows how sub-d surfaces work, how MeshSmooth will smooth out the poly edges. You can see his stack in one of the shots. Doesn't seem all that hard to do.

[Dave Black]

We've spoken at length about getting this type of effect with polys in the "Theoretical Sub-D" sticky thread at the top of this forum.

Give it a read, somewhere around 5 or ten pages into it.

That might at least help your brain get used to the idea a bit.

-3DZ

:D

[lragno]

3DZealot, I've been following the "theoretical sub-d" forum for a while now.

My question has more to do with achieving highly accurate machine parts (i.e. car panels). I just don't think it is possible to do that with simply extruding polys by freehand without guides.

That is why I think the BWM has to have been made with some sort of spline guidance.

[Dave Black]

That's not really an accurate statement.

Yes, spline guides, patches, and NURBS curves would all help. But, it is very much possible to achieve an accurate result using only polys. He is using images as a guide, which can be quite accurate.

I appologize if you have already been following the Sub-d thread, but I thought I'd point you there just in case you had'nt, as it has some very good info on the subject of accuracy.

Can you go into a bit more detail as to what your problem with the technique is, so that perhaps we may actually help you figure it out? It's a bit unintuitive, so don't feel bas or anything. Sometimes it just takes some discussion to make it click...

-3DZ

:D

[EricChadwick]

Looks to me as if loocas is using MeshSmooth at 2 iterations in all his screenshots (first image, 2nd post).

I think if he showed the cage instead it might be clearer what's going on.

[lragno]

Here's a quick example: Splines with Surface...

I think the resulting mesh is too clean to be recreated by freehand poly-extrusion. I could be wrong.:shrug:

[EricChadwick]

Not sure where you're coming from, why you think EP doesn't allow same control as patches.

Here's Editable Poly with MeshSmooth on top.

Orange = EP cage.
Blue surface, white wireframe = MeshSmooth 2 iterations.

Lots of control available. Or am I msising something?

[lragno]

Here's a better idea of what I mean...

Notice the perfect half-circle at the top with the red box.
This was done from an orginal spline shape that was also a circle.

Shapes that require precise lines and curves are easier (it seems) to create than poly-extrusion which relies more on "guesswork" as to where the next edge will go. This is why nurbs are "cleaner".

Anyway, I could be wrong about all of this.......

[EricChadwick]

This is a good thread.

When I work with NURMS there isn't a lot of guesswork going on. Yes, the cage is not a smooth preview itself, as splines are for patches, but switching between NURMS and cage makes it easy to see what's going on. It isn't difficult at all to get perfect curves. csUntangle is a helpful script for this.

The major difficulty I see is that the NURMS surface rarely touches the cage, so the cage can be in quite a different shape. But it was fairly easy once I wrapped my head around it.

[joconnell]

Indeed - polys really aren't accurate at all but we're mainly interested in creating a visualization of something rather than something that's 100% accurate for cad or physical production. It just has to look right. Any time I'm modelling a car or other designed object I try to use as few polys as possible as this makes it far easier to remove bumps in the surface. I let the meshsmooth add in the relevant amount of polygons to smooth it out. If you need something like a perfectly round ar for the wing of a car or some such then I use a primitive as a guide. For example, if I have 6 vertices to make an arch over a wheel, then I'll make a cylinder and align it to the area where the arch is. I can then set the number of sides of the cylinder so that I have 6 vertices for my arch shape - I can then use this as a tracing guide to move my vertices into positions that'll give me a perfect circle arh when smoothed.

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