Pop Drag Force

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Pop Drag Force

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The Pop Drag does two things - 1.  It defines a target velocity.  The particles velocity will gradually pushed to this value over time.  2.  It defines air resistance.  This "air resistance" will define how quickly the particles reach the target velocity.

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    The pop drag is most often used to slow particles down over time.  In the real world, things slow down due to air resistance.  This node is often used to mimic that effect.

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Main Parameters:


-- This acts like an on/off switch.


-  Allows you to isolate the pop axis force based on groups.  For more information about groups, check out the Group Node Bible Entry.

Wind Velocity:

--  This defines the target velocity.  Particles will try to match this velocity gradually over time.

Air Resistance:

--   How quickly will the particles reach the target velocity?  The higher this value is, the faster they reach the target velocity. 

Ignore Mass:

--  If this is checked on, all particles are treated equally.  If this is off, then particles with a greater @mass value will be affected less than particles with a lower @mass value.

Use Vexpressions:

--  Allows you to use vex when altering the wind velocity and air resistance values.

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    Bindings can be used to tell which nodes are allowed to work with each other.  Nodes which belong to the same geometry name are allowed to work with each other.

    As an example, if you set the binding on a pop source to "goobie" and leave everything else at its defaults, no other node in your dop network will want to work with the popsource because they have a different binding name.  If, however, you go to your solver and change its binding to "goobie" as well - now the pop solver will work with the pop source node.  Lastly, if you set a pop force's binding to "goobie", that will now allow the pop force to interact with the pop source node.  NOTE:  Global forces (ex: the Gravity DOP) do not feature any bindings and will work on all data within the dop network.

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    This section deals with a situation which you might run into while using vexpressions.  In vex, you must specify which input to access data from for most functions.  This means 0 = first input 1 = second input, and so-on.  In DOPs, you don't have the ability to plug into those inputs.  Instead, you specify where that data comes from here in the input tab.

Take this example:  Let's say that you want to access a point attribute from the geometry that's plugged into the first input of your dop network.  You could say something like this:  

v@myAttribute = point(0,"Cd",44)

This function can translate to - "I'm looking for a point attribute, read this data from geometry input #0 (which corresponds with input 1 in the inputs tab), I'm looking for an attribute called "Cd", and I want to read this attribute from point #44."

And then, within the Input tab, you can say that the first input argument (which is 0) corresponds to the first context geometry.