Surface - Aperture

Control	Inputs	Defaults
Trimming Volume Outer Boundary
Semi-aperture	X,Y,Z semi-diameters or min/max dimensions of the outer trimming volume.	1,1,1
Center	Trimming volume X,Y,Z center.	0,0,0
Shape	Ellipsoid, Box, Cylinder	Cylinder
Enter as Min / Max instead of semi-ape / center	Toggles entry of absolute minimum and maximum dimensions	Unchecked
Trimming Volume Inner Hole
Semi-ape, offset	X,Y semi-diameters and offset for an inner hole trimming boundary.	Semi-ape 0,0 Offset 0,0
Shape	Box or Z-cylinder	Z-cylinder
Advanced Dot Product Surface Trimming Specification
None Position Direction X/Y/Z axis perpendicular	Establishes the boundaries of a surface based on the local surface normal dot product with a given fixed vector. This would, for example, allow the user to exclude half of a sphere.	None
Reference Vector	Direction cosines of reference vector for advanced dot-product trimming specifications.	0,0,1
Sign of dot product	Positive or negative dot product sign	Positive
Trimming Surface Specification
Operation List View	Lists individual the Boolean expressions for surfaces, collection curves and/or trimming volumes used for trimming. Right-clicking in the spreadsheet area exposes a menu allowing the following operations: •Insert •Delete •Select Entity - opens Entity Picker dialog •AND & •OR \| •NOT ! •Left Paren ( •Right Paren ) •Trim Volume #	Blank
Specification String View	Contains the complete trimming specification string.	Blank

OK	Accept settings and close dialog box.
Cancel	Discard settings and close dialog box.
Apply	Apply settings and keep dialog box open.
Help	Access this Help page.

Application Notes

Combining Trimming Specifications

A surface can be trimmed with multiple surfaces and collection curves using logical statements (AND, OR, grouping parentheses “( )”, and NOT).

Allowed Trimming Entity Types

Although Surfaces may be trimmed with collection curves, they cannot be trimmed with regular curves, ruled surfaces, extruded surfaces, or any other surface that is generated from curves. The reason for this is because the implementation of regular curves, ruled surfaces, and extruded surfaces does not have a mathematical form that allows for quickly evaluating which side of the object the surface to be trimmed lies on.

Example

Volume Trimming Specification

This example clarifies the use of the # Trim Volume operation.

Consider a parabola used to trim a hole in a planar surface as shown below without using the # specification. The trimming operation list for Surf 1 is given by the following:

NOT "!"

.parabola.Surf 2

and is shown in the specification string view to be !".parabola.Surf 2". This specification string should be read as, Trim away the parts of Surf 1 NOT (!) on the positive side of Surf 2.

This trimming specification is determined by the intersection of the parabola's surface equation with the plane Surf 1. Because the trimming uses the parabolic surface equation, the area trimmed from Surf 1 depends on the z-location of Surf 2 as shown below. The mathematical form of the parabolic surface is extended until it intersects Surf 1.

If, on the other hand, we want the hole to remain a fixed size irrespective of parabola's position, the # Trimming Volume specification character # can be added to the trimming specification list. In this case, the outer trimming volume is used to cut the hole rather than the surface equation of the parabola and the trimmed area will be independent of the parabola position as long as the outer trimming volume intersects the plane.

Finally, if we desire that the hole self-adjust its trimmed area as long as the parabola intersects the plane but remain constant otherwise, the two above trimming specifications can be combined with a Boolean OR "|" operation as shown in the following operations list:

TRIM VOLUME "#"

.parabola.Surf 2

OR "|"

NOT "!"

.parabola.Surf 2

and is given in the specification string view as #".parabola.Surf 2" | ! ".parabola.Surf 2". To achieve this trimming operation it is necessary to extend the Z-value of the parabola trimming volume. Note that this has no effect on the parabola dimensions since its clear aperture is dictated by the trimming volume XY dimensions and not the Z dimension.