Weird thing when subtracting

Hi, I have spent the last hour trying to solve this and am stumped, basically I want to subtract from a curved surface to create an hole in the base of this shelter. I figured the way to do this (not sure if there is a command) is to create a block place it inside the curve and then use the trim tool to remove the curved surface where the block intersects it…

however something weird happens to the shape when I delete it, please see the screen shots

as you can see from that above the curve shouldn’t have that line cut through it

this is what I am trying to achieve ^

here is the technical drawings of before and after I remove the surface to explain whats happening

pretty stange… I dont know what I am doing wrong so if anyone could shed some light I’d be grateful!



Can you post the Rhino file?

Have you tried to refresh the render mesh or apply a custom mesh?
This does look like a display problem to me.
To check this you could try to doe a section (intersect a planar surface cutting your part in the problem area).
If the section appears to be okay, it most likely is a problem of the render mesh.

Cheers, Norbert

Hi Cormac,

As it happens to be I have also such anomaly in my render mesh.
@Pascal can you have a look at this.

bad meshing.3dm (110.6 KB)

Cormac, to solve it, the only way for now would be to apply a custom mesh:

Play with the advanced settings to get a mesh that better fits the surface.


Thanks for the help guys, I managed to solve it by exploding the shelter. So when I went to subtract just selected the surface I wanted to subtract and not the whole object. However if I go and join the shelter post subtraction the weird mesh issue comes back, but I’ll just leave it exploded not such an issue.