Flat Shade mode

I would like to know what is actually the purpose of flat shade mode in Rhino. I see that it shows the model like a mesh of polygons but what do we need this for ? I know that, for example, when I render a model, the render engine exports the geometry of the model as a mesh. Is flat shade something that helps to preview what my model would look like when rendered. I would be very thankful if someone could help

I have used it to inspect a mesh before sending out to 3d printing. It shows the actual mesh surfaces instead of an optically smooth one.

I think the same applies when milling from mesh.

So actually it’s in my case to inpect the actual geometry, not the rendered representation.


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Thank you Willem. But for example, when you export to .stl, you have to convert your geometry to a mesh. I know two ways to do this. First is to convert the geometry into a mesh by the Mesh command in Rhino where you can set the smoothness of the mesh. The other way is to select the model and then “export selected” and choose “.stl” . After this there is an option where you also can set the smoothness of the mesh. So, that is why I am confused. Why would I need to see the actual mesh surfaces in Flat shade mode when I will have to choose the smoothness by myself later. I also noticed that when I increase the density of the render mesh quility in Rhino Options it affects the Flat shade mode and therefore, the quality of my renderings…So having that said, probably this flat shade is responsible only for the rendering ? I am still not sure

I think the smarter way to do this is to convert your NURBS object to a mesh in Rhino first (by using Mesh from NURBS Object in the NURBS menu, and then inspecting it using Flat Shade mode. Then simply export as an stl, with the settings such that the mesh won’t be altered. Simply using the slider controls to set the “smoothness” may give you some unexpected results from time to time. What’s “smooth” to some might not be smooth to you. Best to look at the mesh explicitly and in Flat Shade.

Hi Deltoro- when you mesh an object you set the resolution of the mesh but not really its smoothness - that is, it is still a bunch of more or less flat polygons. The usual shading process glosses over this to show you a smooth thing but the real geometry is not smooth.


skyg and pascal, thank you so much. I finally got to understand what is it.

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You’re welcome - BTW, you can get the same effect, on a mesh, by running Unweld at zero degrees - then it will shade as ‘flat’ no matter what, because the information that is used to smooth the display of the mesh is discarded, rather than simply not used.


Yes, I have just tried this. Great…
I am also wondering what is the influence of the Render Mesh Quality in Rhino Options. If I switch the sliders, they will have effect on the surface in shade mode…But will those options have effect after I convert the object to mesh or in this case what matters are the settings of the Polygon Mesh Detailed Options

Hi Deltoro - If you use the Mesh command, then only the settings in that command are used to generate the mesh. The render mesh quality affects only the meshes used behind the scenes for shading and rendering.
Also -

  • You can override the document properties settings in Object Properties - that is customize the render mesh per object.
  • You can get the render mesh using ExtractRenderMesh
  • Analysis meshes (as used in say the Emap command) are separate from render meshes and are generally most useful if set to be quite a lot denser than render meshes.
  • ExtractAnalysisMesh will get that as a mesh object.


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Pascal, thank you again…This will be very useful for me to know

Some pages to read more info:


Thank you Willem. I read the two articles and they were really helpful

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