Snapping Components using Multiple Constraints

 

Multiple-Constraints Snap consists in creating a series of constraints on-the-fly, thereby reducing the degrees of freedom of the components.

One distinguishes four states: 

  • selection of the component to be moved
  • selection of the 1st geometric element, belonging to the to-be-moved component
  • selection of the 2nd geometric element, belonging to the component to which the to-be-moved component will be snapped (henceforth referred to as the receiving component) 
  • a state where the user is asked to accept the proposed solution or to invert the snapping direction
You can now choose among several input selection types in order to specify and filter the pre-selected geometries.
  • Any geometry: The behavior is the same as the default behavior provided in previous versions.
  • Point only: Only points can be selected. Notice that when switching from Design mode to Visualization mode, some points (in fact vertex) are no longer selectable (neither highlighted). To select those points (in fact edge limits), you will have to use the  Characteristic points option.
  • Line only: Only straight edges can be selected.
  • Plane only: Only planar surfaces can be selected. Notice that the plane representation displayed during pre-selection is now centered on the center of gravity.
  • Characteristic points: On curves (lines, circles and curves), you could want to select the mid-point or the extremity points. The pre-selected point is the closest point to the picking point.
  • Arc center: The center of the arc is selected.
  • Picking point: The point on geometry under the mouse cursor is selected.
  • Picking axis: An axis is built, with the picking point as origin and the normal of the picked face or the tangent of the picked edge as Z-axis.
     

The following table summarizes the behavior:

Geometry type selected in combo

Detected geometry
Any geometry line: line
plane: plane (origin in COG)
axis system: axis system
circle, cylinder, cone: line (axis)
sphere: center
curve, surface, volume: picking point
Point only point: point
Line only line: line
circle, cylinder, cone: line (axis)
Plane only plane: plane (origin in COG)
circle: plane containing the circle
Characteristic points point: point
line, circle, curve: start, middle, or endpoint (whichever is closest to picking point)
plane: COG
axis system: origin
sphere: center
Arc center circle: center
Picking point all geometry types: point
Picking axis line: Z-axis
plane, cylinder, cone, sphere, surface, volume: Z-axis normal at picking point
axis system, circle, curve: Z-axis tangent at picking point

 

  Selected Geometry Type
    Any geometry Point only Line only Plane only Character-
istic points		 Arc
center		 Picking point Picking axis
D
e
t
e
c
t
e
d

g
e
o
m
e
t
r
Y		 Point point point     point   point  
Line line   line   start, middle or end point (the closest to the picking point)   point z axis
Plane plane (origin in COG)     plane (origin in COG) COG   point z axis normal at picking point
Axis system axis system       origin   point z axis tangent at picking point
Circle line (axis)   line (axis) plane containing the circle start, middle or end point (the closest to the picking point) centre point z axis tangent at picking point
Cylinder line (axis)   line (axis)       point z axis normal at picking point
Cone line (axis)   line (axis)       point z axis normal at picking point
Sphere centre       centre   point z axis normal at picking point
Curve picking point       start, middle or end point (the closest to the picking point)   point z axis tangent at picking point
Surface picking point           point z axis normal at picking point
Volume picking point           point z axis normal at picking point
Open the SMART_TARGET.CATProduct file from the cfysm samples folder:

SMART_TARGET.CATProduct
Before you launch the Snap command, you should be sure to select a component in the Specification Tree other than the root.

  1. Click the Cumulative Snap icon .
    The Cumulative Snap toolbar appears.
    The toolbar icons are grayed. If the two selected geometric elements are two lines, two planes, an axis system and a line or an axis system and a plane, the toolbar icons will be activated.

    The Cumulative Snap toolbar enables you to invert by rotation around two axes: around the U axis (as was proposed in previous releases) and around the V axis.


The Cumulative Snap functionality does not take the UI-activated component into account. You must explicitly indicate the component to be moved. (If you wish to simulate the UI-activated behavior, you can select the UI-activated component in the specification tree.)
 

  1. Select the component to be moved, e.g. the Disk cylinder.

  1. Select a geometric element (a point, line, plane or axis system) on the same to-be-moved component, e.g. a circle of which the center is the center of the entire Disk cylinder in the sample product.

  1. Select a geometric element on the component to which the to-be-moved component will be snapped, e.g. a circle of which the center is the center of the entire Rim cylinder in the sample product (henceforth referred to as the receiving component).
    The first constraint is created. The Disk cylinder is displaced in accordance with the first constraint. You can continue directly to the creation of the second constraint.

 

  1. Select a geometric element on the to-be-moved component, e.g. the axe passing through one of the nuts of the Disk cylinder.

  1. Select a  geometric element on the receiving component, e.g. the axe passing through one of the nut holes of the Rim cylinder.
    The second constraint is created. The Disk cylinder is displaced in accordance with the second constraint. You can continue directly to the creation of the third constraint.

  2. Select a geometric element on the to-be-moved component, e.g. the plane of the Disk cylinder containing the nuts.

  1. Select a geometric element on the receiving component, e.g. the plane of the Rim cylinder containing the nut holes.
    The third constraint is created. The two components have been placed together as a function of the three constraints.


  1. Rotate to verify that the snap has been implemented as desired.

 

 

Multi-selecting Components
  The goal of this enhancement is to enable the selection of multiple components as input. You must the select all the components (in the product tree or in the 3D geometry) before launching the Cumulative Snap command. Once in the command, you will then be able to select the first geometry to snap from among any of the components belonging to the selected input.
Note the following limitations:
  • Multi-selection is only available before you launch the Cumulative Snap command. If you do not make a selection before you launch the command, the multi-selection will not be available.
  • Other objects currently handled (e.g. shuttles) will not be supported for multi-selection.
 

Multi-selecting Components with Ascendance Relation

Consider the following structure:

If you select [P1.1, P1, P2], you will be able to select a first geometry belonging to P1 (geometry can belong to P1.1 or not) or P2, and a second geometry under P3. The transformation computed to snap the first geometry on the second geometry will then be applied to P1 only, highest father of the sub-set [P1, P1.1] and P2. This ensures that the set of components selected as input to the Cumulative Snap command will be kept as a rigid bloc along the definition of multiple constraints, which is a condition to the definition of a consistent constraints environment.
Open the 5cubes_with_data.CATProduct file from the dmnug samples folder:

5cubes_with_data.CATProduct

 

  1. Keeping the Ctrl key pressed, select Cube.Red, Cube.Blue and Shuttle.1 geometry using the selection trap (by dragging a rectangle to encompass the desired selection), select a face of Cube.Green in geometry, select Cube.Grey, Product2.1, Product1 and Camera 1 in the specification tree.
    You should have something like this:

  2. Click the Cumulative Snap icon .
    The selection will be filtered and only the Cube.Green, Cube.Grey, and Product2.1 components will be highlighted.

  3. Select the top face of Cube.Blue as the first geometry to snap.
    You will notice that selection of the first geometry is possible anywhere except on the yellow cube.

  4. Select the top face of Cube.Yellow as the second geometry to snap.
    You will notice that selection of the second geometry is possible only on the yellow cube.
    The highlighted components can now be moved as a rigid block.