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Mesh to nurb - new findings
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I wanted to share some work I've been doing recently with this function in Shark. Unfortunately we have lost the function in V11, but if you still have V10 you can use it. So a while ago I brought in a mesh, scanned data, used the convert to quads thing, worked OK, still a bunch of triangles then tried the mesh to nurb. Waited a loooooooooooonnnnnggggggg time for nothing to happen. I then started bringing in quad meshes still waited a loooooooong time for nothing to happen. So recently I experimented. I used a program called instant meshes that reorders your mesh in quads. It's advertised to convert high poly to low, but you can ramp up the vertex count and get a dam good mesh from it. So what happens? Instead of the mesh being a bit all over the place, this recorders so its all nice and tidy, and guess what? Mesh to nurbs finds it and converts it a whole load better, faster and with less mess. So the moral of the story, get a nice mesh. You may think this is blinding obvious, but not all meshes are nice, and ordered nicely from top to bottom. And would you think of this first time round? Probably not. Anyway those who are still awake after reading this far, try it and see what you think.
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Smoothly flowing quads make a huge difference in the SubD to NURB tool in v10.
Below is a video I made using the 3D Coat retopology tool.
http://www.csi-concepts.com/Demo/videos/3dcoat.mp4 Tim
Tim Olson IMSI Design/Encore
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Yeah I tried a mesh out of topogun, and the results are good as well. Want to experiment and try to figure out what makes a single surface, so the nurb might be made up from a number of surfaces, I don't like lines :-) :-)
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IntegrityWare, the mesh-to-nurb library providers, do a plug-in for OnShape, part of that plug-in is a manual retopology tool that paints quads onto the underlying mesh, the corners of the quads lie on the mesh. There are at least two similar plugins for Blender that work in a similar way, either free or inexpensive. They're probably more work than automated retopo tools, but they're more controllable and obvious IMO. The brush, magnet and Pacman tools in Instant Meshes are obtuse to me, although reiterative experimentation improves results.
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PowerPack works great with a low poly quad mesh. This is similar to a subdivision in a regular 3D editor. A higher number of polygons gives worse results. Often the surface is uneven and bumpy.
InatantMesh will not give a mirror-smooth surface, but it is quite suitable for organic matter.
I was completely struck by this 3DMax's plugin. It creates a great NURBS from scanned mesh. WOW!
https://youtu.be/INIzKLmvLsI
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Yeah I think there is an element of achieving what is best. My scanner doesn't give a perfect smooth finish on flat surfaces or similar. So when using topogun or similar it's good to check between the scanned mesh and what you're producing to see what the outcome is. Even when I get the surface I tend to best fit off it anyway, the reconstruction is just a guide more often than not
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mesh to nurbs works really, really well from subD models built within Shark/VC. The issues that we have with imported meshes is the conversion from triangular faces to quads. I've also had better results from splitting models into mesh surfaces and converting the surfaces independently. That 3DS MAX plugin is the same IntegrityWare libraries as PPP's. Promo videos show products at their best, naturally. Tim's got a video with a hippopotamus model that's similarly impressive in conversion.
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Yeah that's the trouble like you say. The triangle to quad I don't find too affective in PP, so always try and do my quad meshes elsewhere and fetch them in. I did a test the other day, that threw up some quite large errors on coordinate compare, so need to look into that more and see why that was.
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Using mesh to analytic for mesh models, a plane would ideally have zero deviation, cylindrical surfaces differ between internal and external: internal cylindrical surfaces (holes) should be the largest diameter that'll pass between the facets, which implies that the measurement is a three-point circle taken from the mid-point of the facet edges, ie a circle within a circumscribed figure. External cylinders will be a diameter taken through the end points of the facet edges, an inscribed figure. The reasoning is that holes are sized for clearance, external radii will usually be fillets and refer to adjacent blended faces. Mesh to nurbs is much more vague. This pic is of a car's windscreen manually reverse engineered from an .stl, and it's displayed in Shark and in Marcus Bole's PolyCAD. Should the facets of an .stl be drawn between vertexes that lie on the surface, or does the centre point of the triangle lie on the surface, with the vertexes outside of the hull?
Edited by user Sunday, March 3, 2019 6:33:52 AM(UTC)
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Originally Posted by: murray mesh to nurbs works really, really well from subD models built within Shark/VC. The issues that we have with imported meshes is the conversion from triangular faces to quads. I've also had better results from splitting models into mesh surfaces and converting the surfaces independently. That 3DS MAX plugin is the same IntegrityWare libraries as PPP's. Promo videos show products at their best, naturally. Tim's got a video with a hippopotamus model that's similarly impressive in conversion.
The hippopotamus is an organic mid-poly model. I see no problems for successful conversion. For PP/Shark models up to 70K are not a problem. But models created in the traditional way has more chances. Below is a comparison of traditional and auto-retopologized models. Retopologized models are good too. But their surface is not so smooth.
As for the MAX's plug-in, it converts a high-poly triangular mesh. If PP uses the same library too, then I would also like to convert similar hi-poly models. Maybe not scanned, but for example from zBrush.
By the way, Shark/PP converts easily simple zBrushe's dynamesh models. But solid is not soooo gut. :)
Edited by user Sunday, March 3, 2019 4:55:48 PM(UTC)
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