# Blend Geometry

## Contents

The blend radius refers to the radius of the figurative rolling ball. The blend radius may either be constant or variable. Any combination of variable radius and constant radius blends may exist in a sequence of edges to be blended, as long as they always meet one another with matching radius values.

## Cross Section

A blend between two entities has a characteristic shape which is defined by the cross section of the blend surface. The cross section is the shortest line along the blend surface that connects the two faces being blended. The cross section is always perpendicular to both faces in the blend.

A circular (round) blend has a circular cross section. The cross section of a chamfer blend is a straight line.

## Round Blends

A round blend refers to the surface produced by either of the following:

• Rolling a ball of constant or variable radius along an edge while keeping the ball in contact with the faces to either side of the edge.
• Rolling a ball of constant radius around a vertex while keeping the ball in contact with a face and an edge adjacent to the vertex.

In general, the envelope of the rolling balls path is represented by a spline surface. When possible, it is represented by a simple analytic surface. In either case, the surface is tangent to the two faces and has precise evaluators.

Spring curves follow the point of contact between the pipe and the two faces. The portion of a pipe surface that lies between the spring curves is used to form the round blend face.

Note: The phrase between the spring curves refers to the portion of the surface with smaller arc length.

Blend Face Between Spring Curves

## Chamfer Blends

Chamfering is a ruled surface swept out between the contact points on the support surfaces. The Figure. Chamfer Blend shows an example of a chamfer blend.

Chamfer Blend

Standard Chamfering is contained in the blend component and provides functionality for generating chamfers between analytic support surfaces configured in such a way that the chamfer surface can be represented by a plane or a cone. The size and orientation of the chamfer are defined by specifying an "in-support" distance ("range") for each support. This range is defined to be the distance in the support between the edge being chamfered and the contact point on the support where the chamfer intersects the support as shown in Figure. Standard Chamfering]].

Standard Chamfering

## Vertex Blends

Main article: Vertex Blending

ACIS supports vertex blends and provides a variety of ways to control the shape of the vertex blend surface. Parameters to control the shape (for example, setbacks, etc.) may be passed explicitly, or ACIS may be left to work them out automatically (by specifying autosetback or no parameters at all).