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!

cheers

Cormac

Cormac
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.

HTH
-Willem

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.

cheers