Dense Mesh Models

Hello,

I'm looking for some advice regarding efficiencies when computing toolpaths for dense meshes.

I have some models containing no NURBS, just dense meshes derived from grayscale images. Also known as height maps. The toolpath calculations are taking FOREVER!

Any advice?

Thanks.

Can you decimate the meshes to lighten them up? Here's a tutorial on using Meshlab for that: Decimating Sculpts with MeshLab | Blender Cookie

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Originally Posted by awerby

Can you decimate the meshes to lighten them up? Here's a tutorial on using Meshlab for that: Decimating Sculpts with MeshLab | Blender Cookie

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Hello and thanks for the reply.

I understand. I have worked with these meshes previously for purposes of 3D printing. I use the "Mesh Reduction" command in Rhino on those with great success.

However I am now attempting to create Lithophanes on my CNC router. I generate the beautiful photo mesh using Rhino Emboss. These meshes have photo detail and need to stay "somewhat" dense. See example below. Vectric makes an app called "Photo Carve". I've watched their demo and see their tool paths generated in a few seconds. 3D Lithophanes from photographs

I don't want to buy more software and really believe that RhinoCAM can do this. Do we know for sure that it's the mesh density that is causing the slow computing?

Thank You,

Bernie
Attachment 227096

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Originally Posted by ssw

Hello and thanks for the reply.


I don't want to buy more software and really believe that RhinoCAM can do this. Do we know for sure that it's the mesh density that is causing the slow computing?

Thank You,

Bernie
Attachment 227096

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That would be my guess. What happens when you run Mesh Reduction on these files?

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Originally Posted by awerby

That would be my guess. What happens when you run Mesh Reduction on these files?

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Hi Andrew,

My mesh reduction tests were inconclusive, because the tool path calculations never completed. I had to cancel them before they finished. I let one go for almost 2 HOURS before I killed it.

I have made some progress though. I'm finding that it's not the number of triangles that causes the problems. It's how tight they fit in a given area. This is defined as the "resolution". I should have known that! For example, 1 million polys in a 2 cm x 2 cm area has issues, but 1 million polys in a 20 inch x 20 inch area works okay.

So, I think I'm on the right track.

Thanks for the help.

-- Bernie

Quote:

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Originally Posted by ssw

Hi Andrew,

My mesh reduction tests were inconclusive, because the tool path calculations never completed. I had to cancel them before they finished. I let one go for almost 2 HOURS before I killed it.

[I was thinking you'd reduce the mesh before trying to do the toolpaths. If that's what you did, I'd say the test was conclusive, but negative.]

I have made some progress though. I'm finding that it's not the number of triangles that causes the problems. It's how tight they fit in a given area. This is defined as the "resolution". I should have known that! For example, 1 million polys in a 2 cm x 2 cm area has issues, but 1 million polys in a 20 inch x 20 inch area works okay.

[That seems odd to me; I'd look for another explanation. After all, the program can use mm or inches, and has no internal check to see which is being used for a given operation, so 20 inches would be the same as 20 mm as far as it's concerned. Have you looked at your Rhino tolerances? Maybe they're set too high.]

So, I think I'm on the right track.

Thanks for the help.

-- Bernie

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[Let us know how it goes. Have you asked Mecsoft's tech support about this? ]

[That seems odd to me; I'd look for another explanation. After all, the program can use mm or inches, and has no internal check to see which is being used for a given operation, so 20 inches would be the same as 20 mm as far as it's concerned. Have you looked at your Rhino tolerances? Maybe they're set too high.]

Yes, you are right (sort of). The mesh is just data. It has no real size, as data. So, inches or mm don't matter.

BUT... as soon as we apply a physical size to it, it becomes a "resolution". The details that we are asking the cutter to follow are "resolved" based on the physical size.

An easy way to see this is to take the exact same mesh and cut two different blocks of wood. One 20 mm square and 20 inches. Compute tool paths with the same 1/4" cutter. THAT is where things become obvious.

I hope this makes sense.

-- Bernie