Maxim,
Thank you for your response. Your instructions are generally correct, as usual. This note will offer some details to others who may be inclined to go in these directions...
1) Since I tend to work in 3D, I have generally selected (3D) Wireframe as my rendering mode (upper left corner of the display area). That may be fine for small models, but when the number of elements in the model increases greatly, it can dramatically sloooooooooow down interactions with AutoCAD. For example, my model contains 36,482 facets. It can take almost a minute just to select the whole model, and the process of swiping across the model is then interrupted by the cursor freezing and the little rainbow circle showing until the program catches up with your mouse cursor movement. This is not a pleasant situation.
The cure is to use 2D Wireframe rendering. In this rendering mode, selection of my whole model is nearly instantaneous. So far, the only drawback (to someone who is used to the 3D Wireframe environment) I have encountered is that the 3D Gizmos do not display... at least not upon selection of an object. They DO show up when you invoke a 3D command on a selection. E.g., 3DROTATE causes the 3D Rotate Gizmo to display for the duration of that command. So the Gizmos are still available, even though you're in a 2D rendering mode.
2) The AutoCAD for 2013 manual's help page for DELOBJ states that its default value of 3 has the result that it "Removes all defining geometry for CONVTOSOLID, CONVTOSURFACE, CONVTONURBS, and CONVTOMESH commands." The CONVTOSURFACE help page states that it may be used to convert "Planar 3D faces" to Surface objects. Combining those two, one naturally expects that the result of a CONVTOSURFACE command on a collection of 3DFace objects will be a Surface, and the 3DFace objects will be deleted. In my experience, the Surface is indeed generated, but the 3DFaces remain.
For example, following your suggested sequence of actions, here is the console output from a run I made... just prior to hitting the ENTER key to perform the final UNION. It follows the sequence in my original posting. Notice that during the CONVTOSURFACE action, the console reports finding all 36482 facets in my model. But when I start to perform the UNION, and I make the selection, the console reports twice as many items found: 72964. This is because after the CONVTOSURFACE, the original 3DFaces are still there.
Opening a Release 12 DXF file.
Regenerating model.
AutoCAD menu utilities loaded.
AutoCAD menu utilities loaded.
Command:
Command:
Command:
Command:
Command: *Cancel*
Command: *Cancel*
Command: _vscurrent
Enter an option [2dwireframe/Wireframe/Hidden/Realistic/Conceptual/Shaded/shaded with Edges/shades of Gray/SKetchy/X-ray/Other] <2dwireframe>: _w
Command: _3DORBIT Press ESC or ENTER to exit, or right-click to display shortcut-menu.
Command: CONVTOSURFACE
Mesh conversion set to: Smooth and optimized.
Select objects: Specify opposite corner: 36482 found
Select objects:
Command: *Cancel*
Command: UNION
Select objects: Specify opposite corner: 72964 found
If you don't know that DELOBJ is not working as it should, that doubling is quite confusing.
The solution is to zoom in closely on the results of the CONVTOSURFACE, select a Surface element, then right-click and Select Similar to select all of the Surface elements together. Then right-click again to Move To Layer. Hide that layer and thus the original 3DFace objects are displayed, and can be deleted.
3) The computational time required for performing an action such as the UNION command on a set of Surface elements is apparently proportional to the SQUARE of the number of elements. That can have serious consequences. It means that the final UNION of all 36,482 Surface elements can take HOURS. And since there is no indication offered by AutoCAD of the estimated time to completion (hint, hint!), the user cannot tell the difference between a slooooooooooow but successful run and one that has irretrievably hung.
The solution is to divide the problem into smaller pieces. Then the power law won't bite so badly, and the pieces can be joined in a later command.
4) As it ends up, the UNION command is much slower than an alternative processing route. Granted, you answered what I asked, but I have discovered that some ways are faster than others. Fortunately for my needs, I can use solids. I know I asked you how to get to a mesh from my 3DFaces, but the real answer is that I should avoid doing that directly, because the UNION command in AutoCAD is so slow.
The solution is to use SURFSCULPT. I put caps on the open ends of my mesh, use CONVTOSURFACE, then SURFSCULPT, and the whole process proceeds much more quickly. The square law still holds, but the general rate is much faster.
5) Because I had spent so much effort in generating my own mesh, I really trust my own data. Thus I decided to set SMOOTHMESHCONVERT to 3. This caused the resulting Surfaces to not be watertight. I had to reset the variable to 0, and then I got watertight results. For those who haven't yet attempted it, converting surfaces to solids via the SURFSCULPT command requires watertight Surfaces. At this writing, I have a leak in my generated data, and I am using SURFSCULPT and good old binary cut to try and locate it. I will have to fix it before I can continue.
That's all so far. I'll post again as soon as I know more.
Again, thanks for your help.
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