ClipGeom

DESCRIPTION

ClipGeom takes a single geometry input and adds a clipping plane at the chosen position. The effect of this plane, once the output is wired to the Render module, is to clip any geometry to the half-space defined by the plane field (i.e. any geometry within the other half-space is not drawn). The half-space is the side of the plane in the direction of the plane normal. The clip direction is considered to be in the direction of the plane normal. Having a clip plane allows the internal inspection of generated geometry without the need for cropping of the original data and re-visualizing. It only affects the geometry that passes through it, leaving other geometry in the Render module un-clipped.

The plane is initially positioned at either the centre of world coordinates (0,0,0) or the centre of the bounding box of the input geometry (selected by the 'Centred At' widget). This is the centre point about which any rotation subsequently occurs. The initial clip direction is along the negative X axis, that is to say that any geometry in the negative X half-space will be clipped. This can be altered to clip along the negative Y direction by setting the 'Initial Clip Direction' widget to 'Along Y'. Clipping along negative Z is set similarly. The centre point and direction of the clipping plane can subsequently be altered by means of an input transformation matrix as created by the TransformGen module. The (XYZ) translations are added to the initial centre point and the rotation then applied to the clipping direction to orient the clipping plane. Further, using the 'Distance from Centre' widget, the clip plane can be moved a distance along the clipping direction.

Ordinarily the clipping plane has no geometric representation, but to make orientation easier, a representation can be added. The chosen representation is selected using the 'Representation' option menu. When a representation is being used, lines extending from the corners show the direction in which clipping will occur (i.e opposite to the clipping direction).

INPUTS

Port: Geom
Type: Geometry
Optional: This port is optional.

Input geometry to be clipped.

Port: Xform
Type: Lattice
Optional: This port is optional.
Constraints: 2-D
Constraints: 1-vector
Constraints: float
Constraints: uniform

This is a transformation lattice as generated by the TransformGen module. It contains an offset which is added to the centre point and a rotation which is then applied about the new centre point. (The centre point is as defined above.)

WIDGETS

Port: Centred At
Type: Option Menu
Menu Item: World Coords (0,0,0)
Menu Item: Centre of Bounding Box

The initial centre point for the clipping plane.

Port: Initial Clip Direction
Type: Option Menu
Menu Item: Along X
Menu Item: Along Y
Menu Item: Along Z

Sets the initial clipping direction to be along either the negative X, Y or Z axis. Any subsequent shift or rotation as supplied by a transformation matrix is applied to this vector.

Port: Distance from Centre
Type: Slider

Sets the distance travelled from the centre point along the clipping direction (after any user suplied transformation matrix has been applied) before the clip plane is positioned.

Port: Swap Clip Direction
Type: Option Menu
Menu Item: False
Menu Item: True

The clipping direction can be flipped to clip in the opposite direction.

Port: Active
Type: Option Menu
Menu Item: False
Menu Item: True

The effect of the clipping plane can be turned on (default) or off without having to actively move it from its current position.

Port: Representation
Type: Option Menu
Menu Item: None
Menu Item: Outline
Menu Item: Plane

Since a clipping plane has no geometric representation by default, an artificial one can be added. This can be either an outline or a semi-transparent plane.

Port: Representation Size
Type: Slider

The size of the representation can be controlled using this slider.

Port: Just Move Representation
Type: Option Menu
Menu Item: False
Menu Item: True

In cases where the geometry to be clipped is very large, moving the actual clipping plane may take some time. Setting this widget to True allows just its representation to be moved. Once the desired position is found, just reset the widget value to False for the new position to take effect.

OUTPUTS

Port: ClippedGeom
Type: Geometry

The clipped input geometry and any geometric representation that has been created.

KNOWN PROBLEMS

Wiring the output geometry into other modules with the 'Just Move Representation' widget set to True causes a Receiver error to occur. This can fixed by simply setting the widget to False and then back to true again.

SEE ALSO

TransformGen ClipGeomOrth ClipGeomWedge


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