[SOLVED]A Clean Inner Extrusion?

[Atom]

Hi All,

 

I have a sphere that I have clipped. I want to extrude the sphere inwards so it looks like it has some thickness once we see inside. I have used a PolyExtrude and it does work but the outer faces get messed up and it is no longer sphere like along the outside. What is the trick to extruding without destroying the outer faces?

 

NOTE: I don't want triangles or squares to show on the outer surface, just a clean continuous sphere-like surface.

Edited September 16, 2015 by Atom

[Skybar]

PolyExtrude SOP?

 

edit: Right you tried that, sorry. Why isn't it working? Works fine for me.

extrude_dv.hipnc

Edited June 12, 2015 by Skybar

[jrockstad]

From that screenshot it seems you are actually using the Extrude SOP and not PolyExtrude. From what I understand Extrude is primarily meant to be used with text and other simple curve shapes, so if you're working with a polygonal mesh, stick with PolyExtrude. 

[Atom]

Correct, jrockstad. I was using Extrude instead of PolyExtrude.

 

However, even if I use PolyExtrude I still cannot achieve the goal of a smooth outer sphere with a sharp clip edge. I added a Facet and unique points which gets me the sharp edge but the inside of the sphere is faceted as well (red). How do I get both options in one object? (i.e. it has to render well)

Edited June 14, 2015 by Atom

[jrockstad]

Try adding vertex normals to your mesh. There are a few different ways to do this including the Facet SOP which you're already using, but I like to just use the Normal SOP. Smoothing / subdividing should also give you a cleaner rendered mesh.

 

Clarification: I misspoke - you're not actually adding vertex normals by cusping polygons with the Facet SOP, but you achieve the same effect as doing do. Only the Normal and Vertex SOPs will actually apply vertex normals. 

Edited June 13, 2015 by jrockstad

[Skybar]

Instead of unique-ing all the points with the Facet SOP, turn on Cusp Polygons and adjust the cusp angle.

[Atom]

@Skybar: Thanks, that is close but the render still has anomalies. @ jrockstad: I tried the Normal and Vertex SOP as well and they produce final geometry that does not render correctly either. Very similar to the Facet cusp solution.

 

NOTE: Changing the Frequency on the Sphere will repair it for a fixed clip distance but as soon as I move the clip distance (I want to animate it) the Frequency no longer works and the anomalies appear again.

ap_clipped_sphere.hipnc

Edited June 14, 2015 by Atom

[Guest tar]

Try 'holeSOP'. See attached:

ClippedSphere.hipnc

[Atom]

Thanks Marty, I think that does it!

 

I like the fact you added an inside color as well.