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Ortho Knife for AC3D


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Acts on the edges of the selected objects/surfaces, inserting a vertex where necessary.

This utility was written to provide a way to create/use knives that differs slightly from the original knife utility. This version is more suited toward adding details to geometry, while the original version is better for cutting objects apart.

Differs somewhat from the knife utility:

Attribute Ortho Knife Knife
Select mode Works in any select mode Must be in Group or Object select mode
Slicing surfaces Does not slice surfaces, but can auto-select new vertices so an AC3D Slice can be issued. Slices surfaces, but only across a given knife edge (does not span slices across different edges).
Cut away objects Does not cut away objects Can cut away objects
Inserted vertices per edge Only one vertex may be inserted in an edge. Multiple vertices may be inserted in an edge.

This plugin and code are freely distributable

AC3D versions prior to version 5 have not been tested with this script.

The interface options are as follows:

Set knife Establishes the knife object. The knife object is an AC3D object that will be used to determine where to insert vertices. Any place the knife objects intersects the geometry in one of the Orthographic views, a vertex will be inserted (see below for caveats).
Select new vertices If this option is checked, new vertices will be auto-selected. If you are not in vertex select mode, then vertex select mode is auto-activated.
Delete entire knife object If checked, the knife object will be deleted.
Slice front (XY) If clicked, selected geometry is cut .


Copy the orthknife.tcl and orthknife.p files to your AC3D plugins folder (for example, if using Windows, C:\Program Files\AC3D5\plugin) and (re)start AC3D.

You will find the "Orth Knife..." menu item under the "Tools" menu.

Example : Slicing a cube

In this example we'll slice a cube across an arbitrary plane.

Create a box, then draw a simple line that completely intersects the box at an angle. I created a line on the "front" view.

We'll slice the box where it is intersected by the line in the Front view, then delete the line. To do this, perform the following steps:

1. Select the "Ortho Knife..." menu item under the "Tools" menu. This brings up the Ortho Knife interface.

2. Select the line object and click "Set knife" to make the line your knife object.

3. Ensure that "Select new vertices" and "Delete entire knife object" are checked. "Delete entire knife object" will cause the line to be deleted.

4. Select the box and click "Slice Front (XY)".

The button you click determines which view will be used when determining whether the knife slices an edge.

If you followed these steps, you should end up with new vertices in the box as shown below.

At this point, you can perform a Vertex -> Slice Surface (Ctrl+Shift+L) to slice the surfaces:

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All content Copyright © 2006 Dennis Hawthorne, except where explicitly noted
supercoldmilk © 2006 Dennis Hawthorne