Solid Union, Difference, and Intersection errors / unexpected behavior

Hello,

Could someone please clue me in on what the limitations of the solid tools are in Grasshopper? I am trying to use Grasshopper to process and expand upon geometry from Rhino, Revit, Sketchup, etc. and I need to be able to boolean some objects together. However, I seem to keep finding instances where the boolean operations unexpectedly fail (see screenshots for some examples). I haven't been able to find any more in-depth info on how the Solid Tools work so I hope someone can help me out. Thanks!

Example one: I want to subtract the inner extruded shape from the rectangular extruded shape, but the difference component doesn't seem to like that single edge of the smaller shape touching the outer surface of the box.

Example two: I have a list of Breps I want to union, but it doesn't work unless I either bake them first or jitter the list, and even then the Brep is "Invalid" but appears normal when baked. Not sure what "invalid" means in this context.

Replies to This Discussion

Permalink Reply by Armin Seltz on January 14, 2016 at 3:46am

Have a look at this discussion: http://www.grasshopper3d.com/forum/topics/solid-union-fails-with-so...

I think its the same things I noticed. Basically giving everything the slightest bit of variation helps!

Permalink Reply by martyn hogg on January 14, 2016 at 6:15am

Always try and use closed breps and avoid intersections where you get parallel surfaces or intersections that may result in very thin, pointy surfaces.

Permalink Reply by d3athcarb4fatty on January 14, 2016 at 10:53am

Thanks for the input Armin and Martyn! I don't think I will be able to completely avoid those parallel surfaces or thin slivers of surfaces, so maybe my best option would be to add on an extra definition that can locate breps that are likely to cause problems and add enough "noise" so that they can intersect properly.

Since we are talking about intersection issues, is the following another example of a symptom of the same issue? This involved taking a number of co-planar surfaces and dividing them up into fragments based on where they intersect. I think I am having a similar issue as this guy did in this other discussion, but I don't think his was resolved: http://www.grasshopper3d.com/forum/topics/surface-split-tolerance-p.... It doesn't seem to be a floating point error because tolerance settings make no difference.

I am using an older version of Grasshopper (my Rhino 5 trial expired long ago), so if anyone could open up the model real quick and check if the behavior is the same for you, it would eliminate that as the source of the problem.

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