Experimental:Force POP

Summary

The Force POP is used in a Particle POP loop and outputs a float3 attribute named PartForce that sums a set of forces defined in the Force POP.

The forces include, first on the Global page, a single global force, plus a Wind Speed converted to a wind force.

These forces are by default uniform for all particles, but because it can be affected by attributes on the Map page, each particle (point) can have a different global force or wind speed applied to it.

Currently the conversion of wind speed to wind force is hard-wired in the Force POP, but more detailed control will be provided in a future build.

On the Force (Local) page, you can choose between Radial, Axial, Vortex and Spiral local fore types, with position (Translate), Direction, rolloff (Radius) and Strength controls. The global and local forces are added together.

In one Force POP, the local force is added to the global and wind forces to generate the PartForce attribute. If the input of the Force POP already exists, then the Force POP's sum of forces is added to the input's PartForce.

Thus you can string a bunch of Force POPs together and mask each one with a Field POP.

Assuming PartForce is in the (usually Null) POP at the end of the Particle POP's feedback loop, PartForce feeds back to the Particle POP where it is used to calculate all particles' velocity and position on the next frame of the simulation.

However you can define multiple local forces in one Force POP: To enable many forces to be included in one Force POP, the parameter called Spec POP is a pointer to, usually, a Point POP, where each point of the Point POP defines a separate local force, where the attribute names are matched to the the parameter names (for example, attribute strength represents the Strength parameter). In the Point POP you need to create the appropriate matching attributes.

Then the sum of the local forces are added to the global and wind forces to generate the PartForce attribute.

Note that you can create the PartForce attribute any way you want - using Noise, Math Mix, Pattern, Lookup, GLSL POPs etc. You don't need the Force POP - it is just a convenience.

See also Particle POP, Field POP.

forcePOP_Class

Parameters - Force Page

Parameters - Map Page

Parameters - Common Page

Operator Inputs

• Input 0: -

Info CHOP Channels

Extra Information for the Force POP can be accessed via an Info CHOP.

Common POP Info Channels

Common Operator Info Channels

• total_cooks - Number of times the operator has cooked since the process started.

• cook_time - Duration of the last cook in milliseconds.

• cook_frame - Frame number when this operator was last cooked relative to the component timeline.

• cook_abs_frame - Frame number when this operator was last cooked relative to the absolute time.

• cook_start_time - Time in milliseconds at which the operator started cooking in the frame it was cooked.

• cook_end_time - Time in milliseconds at which the operator finished cooking in the frame it was cooked.

• cooked_this_frame - 1 if operator was cooked this frame.

• warnings - Number of warnings in this operator if any.

• errors - Number of errors in this operator if any.

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