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This blends transforms on the source primitives in the first input with transforms from target primitives in the second input, using a list of weights specified in the parameters.
This node works similarly to the the Constraint Blend CHOP, but each successive blend re-uses the same target primitive’s transform, allowing you to blend the individual components of the transforms by varying amounts.
Currently, USD does not support constraints. Parametric constraints are probably antithetical to USD’s design mission of being descriptive, immutable, and idempotent.
As a layer above USD, that generates USD, the LOP network can compute dynamic constraints, and “bake” the results as time samples when it writes the USD to disk.
Tips and notes
You can’t use a nested point instance as a source. You can use a nested point instance as a target.
When you specify multiple source primitives, the node blends each source transform with the corresponding target primitive at the same index in the list of targets.
If you specify fewer target primitives than source primitives, the node blends the source primitives without a corresponding target primitive into the last target primitive.
For example, if you specify three source primitives,
/cube1 /cube2 /cube3, and one target primitive
/sphere1, the node will blend all three cube transforms into the sphere’s transform.
If you specify three source primitives,
/cube1 /cube2 /cube3and two target primitives,
/sphere1 /sphere2, the node will blend
sphere1, and both
Whether the source prims are regular primitives, or point instances.
This node does not support nested point instances as sources.
When Source ▸ Type is “Point Intance”, the point instance to use, using
/path[instance_index] syntax (for example,
Whether the blend targets are the same as the source, regular primitives, or point instances.
You can use a nested point instance as a target.
When Source ▸ Type is “Primitive”, the scene graph path to the prim to use.
When Target ▸ Type is “Point Intance”, the point instance to use, using
/path[instance_index] syntax (for example,
Specify the frame at which the source and/or target geometry are imported into the embedded sopnet to build the constraints. The default “$FF” expression forces the constraint LOP to be time dependent, which is needed when operating on a non time-dependent network that has time samples driving the source or target primitives. However, for better performance with a non time-dependent network with no time samples, it is recommended to use a static value instead.
How to blend the transforms.
Each blend source contributes to the result according to its blend weight. If the blend weights do not add up to one, they are normalized so they do.
The first prim is the “base”. The blend weight associated with the first prim is ignored. For the other blend weights, if a blend weight is
0, the result is the base.
There are blend channels for all the other inputs, and when they are all zero, the output is the base. If any one input’s blend weight is
1 and the others are zero, that input is the output.
The advantage of the Difference method is each blend input affects the result without reducing the effect of the others. You can exaggerate beyond each of the inputs by setting their blend weight higher than 1. You can also use negative values. When all blend weights are 0, you get smooth transitions as any of the blended channels ease out of zero.
Rotation channels typically don’t blend well when treated as Euler angles, and straight linear blending can result in flips and odd rotations. Instead, shortest path blending can be used to properly blend orientations represented by Euler rotation angles.
Rotation channels are blended like any other channel.
Shortest Path (Linear)
Two inputs are blended using shortest path rotation blending. If more than two blend inputs are connected, use Fast Linear.
Shortest Path (Fast Linear)
Multiple inputs are blended together using shortest path rotation blending.
Set this to the number of blend weight you want to set for the prims selected above.
How much weight to give this transform when blending. The interpretation of this value is different when Method is Difference.
For each blend, select which components (
TX,TY,TZ,RX,RY,RZ,SX,SY,SZ) to blend.