Flipped Surface Normals

lately i have been having this issue again when the output surfaces have their normals showing down. talking about Loft, Edge Surface… with SrfPt. i can at least create the surface CCW if i know the right from the start.

only Network Surface seems to deliver a surface with the normals showing into the “right” direction. i noticed this lately because turning on zebras did not reveal anything, till i understood that its on the inside or on the lower side of the surfaces, so most of the surfaces have lighter colors and need the normals inverted.

Hi Richard - in general there is no good way to predict on what side surface normals will fall. Rhino can’t guess what side you consider to be outside, in other words, to monkey with the normals.


well there seems to be some logic actually… with some mess,

try Srf Pt, if the surface you create is on a cplane then making 4 points CCW always puts the normals into ones face. while creating the points CW they show away, feels like kungfu if you know it.

but if the input curves for an extrude or a loft are drawn towards the left of the cplan the normals show to the bottom. that feels unlogic they should show up then, or at least have them all behave the same way, because if the input curves are drawn towards the right side they show up.

Recommended -> if you have allways activated different “backface color” in shaded view, you see all surface direction’s quickly…(this setting should be standard)
See under "Backface Settings"

hi eddi thanks, yes i have that activated, its just very slight with the colors i use so not always distinguishable and less important than the unlogic or lets say messy behaviour of how the normals get actually produced.

Hi Abend, You’re right, not all surface commands follow the same logic, but i’m annoyed only when the UVN needs to be aligned, example for _FlowAlongSrf …