Possible to draw a sphere with normals in?

This is mostly academic, I have an acceptable workaround, but I’m curious what the ideal solution would be.

Is there any way to break the common edge of a sphere so you can point the normals in? Like how do you make it into a surface with two coincident edges instead of auto-closing and forcing the normal direction.

For example if you were rendering a rocket and wanted to use a sphere to put a bitmap of stars on it with the rocket model in the middle.

Hello - no - a solid always points outward in Rhino. A mesh sphere can point inward.


you don’t need to flip the normals to render a sphere with a texture on it. or I’m missing something.

It can be important for rendering, as the normal direction determines which way light is emitted with emissive materials. Or… Unreal (for example) doesn’t render backfaces at all. So if you want it to render the normals have to be facing the camera.

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I guess the easiest way is to make a tiny hole somewhere to get an open srf and then flip the normals

Yes, exactly. Just seems like an arbitrary limitation imposed for a “feature” that seems wholly un-useful.

I mean… please correct me if I’m wrong but the notion of a “solid” is sortof a hallucination with nurbs, correct? Rhino has to deliberately check if the surface/polysurface is closed then lock out the normal direction. What is the situation where this behavior is helpful?

I see the shell thing come up on the forum all the time. What’s so wrong with just letting us put normals the direction we want? I don’t mind if volume barfs on inside out closed shapes.

I’d love to know the logic here just as a curiosity.

Hello - for one thing, it makes Boolean operations predictable.


Isn’t that sortof a beginner issue?