I would like to cut through a model with a plane and get a resultant outline of the model where the plane slices through it. For example if I use a plane to slice the corner off of a cube I expect to see a line in the shape of a triangle. How do I do this in Three.js ? I am used to doing this in …

[image] BCoggins: It appears that in Three.js they really don’t want you to have access How rude of them! :smile:

Not so much RUDE as inconsiderate. After all it’s me!?! :grin:

I think what you’re looking for is called “clippping”, and there are a few demos of this in the examples section . This doesn’t provide the outline you require, though, since the clipping is calculated in the shaders, so you don’t really have access to the points or vertices on the JavaScript side. Y…

I appreciate the help. I’ll take a look and see how it fits my needs. On the surface it appears that Three.js is a graphics tool with some geometric calculation abilities but not a full-throated ability. I don’t mean that as a knock, just that it may be a screwdriver and I really need a hammer. …

If you really just want a visual outline of where the model was trimmed you can use the Material.clippingPlanes field as @marquizzo suggested and then write a custom shader to highlight the edge that was clipped by computing the distance to the clip plane at every fragment. But yes generally three.…

Thx. I would like to get the cross-section of the 3D model I have so that a parametric 3D model can be reconstructed and used for engineering analysis. It sounds duplicative but what gets built often varies from the design. Or sometimes you have something that was built before the era of 3D models …

[image] BCoggins: I’m new to three.js so I’m still figuring out what is what. My comfort zone is creating the CG libraries/capabilities. hofk posted some links that might help but if you have suggestions as well, I’m listening. You need: 1- GUI to transform the plane. 2- A fast and efficien…

I can’t disagree with good advice.

Creating a cross-section outline

Questions

hofk February 17, 2021, 9:15am 5

This example still works with the old Geometry, not BufferGeometry from r125. You have to rewrite it.

From the Collection of examples from discourse.threejs.org

discourse.threejs.hofk.de 2018

Topic		Replies	Views
Section A Model Questions geometry	8	2472	September 7, 2022
Material clipping plane color and shape outline vertices Questions clipping-planes	12	3835	May 26, 2022
Creating a cut section with a filled surface Questions geometry	2	486	August 20, 2024
Cut a shape out of a plane Questions geometry	3	5611	June 27, 2018
Regarding Threejs, using clippingPlans cannot clip the concave parts of the model Questions geometry	12	370	November 11, 2025

Creating a cross-section outline

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