Menu : TRIM

Command: Blend:Variable Radius

Shortcut : None

This command creates a variable radius rolling ball blend between the target surface and another surface, which must intersect. In addition, it trims the surfaces where the blend touches the surfaces.

The blend surface created by this command resembles part of the surface of a ball rolling around the two surfaces. The blend surface has a varying radius circular cross-section and it joins the two surfaces tangentially.

For this command, the target surface is called "this surface". The second surface is called "other surface".

Normally pointing and clicking with the left-hand mouse button after executing the command indicates the other surface. Sometimes it may be difficult to point exactly at the surface that you want. The alternative way is to click any key on the keyboard, which brings up a dialogue box in which the name of the element where the surface is located and the number of the surface is entered.

Before computing the actual blends, the program computes the intersection(s) between the two surfaces. If there are several intersections DeskArtes displays numbers on each intersection, and asks for which intersection number you wish to calculate the blend.

The command next displays a series of arrows on the two surfaces that will be used to indicate which blend surface is to be calculated.

A parameter box is then displayed requesting the radius of the blend and the direction of the blend. Choosing whether the ball will be rolled on the side of the surface pointed to by the arrows (normal side) or the opposite side (opposite side) indicates the direction. This needs to be indicated for both surfaces giving four possible combinations (normal-normal, normal-opposite, opposite-normal and opposite-opposite) producing four possible blends as represented below.

The radius values now need to be defined. This is done graphically by pointing and clicking with the left-hand mouse button at a position on the trim curve and then typing in the desired radius value with the dialogue box that appears. Repeat this process, defining new radius values at as many different places as required. If you need to pan whilst defining the radii, you may use the middle mouse button to start the normal panning operation.

To end the radii definition process, select the ready to blend option in the dialogue box or press any key on the keyboard. The program then computes the blend surface. Click the right mouse button to cancel the blend operation.

If there were multiple intersections, the command cycles through the above operations allowing you create blends at each intersection if required.

The calculation of the blend is a mathematically very complex operation.

Note: Variable radius blends are tolerant of sharp corners if small radii blends are used.