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The main purpose of this node is to extract a ballistic projectile’s position at a given time. However, it can also be used to extract points from many curves in custom patterns for abstract effects.
Tips and notes
You can use the Edge Transport SOP to create a point attribute on a curve containing the distance along the curve at that point. This is useful as a “cutting” attribute for this node.
This node discards the input geometry and only outputs the “extracted” point(s). This is mostly useful in a technical workflow where you branch off the geometry to this node to find the point, and then use the point as an input to another node.
You can measure at any point along a curve. Even though attribute values are only stored at the points, when you read the attribute at an arbitrary distance along the curve, Houdini interpolates the nearest point attribute values.
You can extract other attributes besides the point position at the “cut point”.
Curves with Cut Attribute
Primitive curves with point attributes providing a distance attribute.
Create a new disconnected point at the position on the curve where the interpolated value of this attribute equals the Cut Value below.
How you specify where on the curve to generate a new point.
The node creates a point where the value of the Cut Value parameter below equals the value of the Distance Attribute.
Specify a primitive (per-curve) attribute in the Cut Value Attribute below. The node creates a point for each input curve where the value of that primitive attribute equals the value of the Distance Attribute.
This lets you specify a different cut value for each curve.
Use the current time (in seconds) as the cut value.
This is useful for extracting a projectile’s position from its trajectory generated by the Ballistic Path SOP, in which case you would set the Distance Attribute
When Cut At is Constant Value, the attribute value to look for along the input curve(s).
Cut Value Attribute
When Cut At is Attribute Value, this primitive (per-curve) attribute should contain the value to look for along each curve.
A space-separated list of attributes to copy from the curve onto the new point(s). The default is
P, meaning the 3D point position where the attribute matched.
When the checkbox is on, create an attribute on the generated point(s) containing the fractional position (between
1) along the curve where the point was found. For example, if the point was extracted from one-third of the way along the curve, the node would set this attribute to
0.33 on the point. The default attribute name is
Number of Cuts
When the checkbox is on, create an attribute on the generated point(s) containing the number of cuts on the source curve. The default attribute name is
ncuts. This is off by default.
When the checkbox is on, create an attribute on the generated point(s) containing the primitive number of the source curve. The default attribute name is
curvenum. This is off by default.
Copy Input Primitive Attributes
Turn this on to copy primitive (per-curve) attributes from the source curve onto new points generated from that curve.
When Copy Input Primitive Attributes is on, this is a space-separated list of primitive (per-curve) attribute names/patterns to copy from the source curve onto new points generated from that curve.