• Maxon Cinema 4D

  How do I emit particles based on a splines point animation speed?

  Posted by Ben Black on December 11, 2014 at 2:11 pm

  Hello,

  I have a spline which has animated points moving up and down.

  I would like to emit particles from the spline, but have the amount emitted be influenced by the speed at which a particular point is moving.

  So the faster a point is moving, the more particles it emits.

  That make any sense?

  Easy enough to do based on a standard emitters position and speed but can’t work out how to access the spline information to get this working properly.

  Many thanks in advance.

  Cheers,
  Ben

  cargocollective/benblack

  Ben Black replied 11 years, 5 months ago 2 Members · 2 Replies
• 2 Replies

• 

  Adam Trachtenberg

  December 11, 2014 at 6:36 pm

  I don’t think you can do it with a standard emitter because it isn’t intended to allow animation of the birth rate. You’d probably have to use Thinking Particles.

  To set the rate you have to determine the speed of the point. You can do that by feeding the point’s position into an Xpresso memory node. The memory node allows you to output the value of a parameter at an earlier time. So if you input point position and set a history depth of 2 and Level 1, you’ll get the point’s position at the previous frame.

  Now you can use the distance node to measure the distance that the point covered in a single frame. That in effect gives you what you need for speed, since speed is Distance/Time. So you can feed the memory node output directly into the PStorm’s rate input, or you can pipe it through a range mapper for more control.

  Example: 8290_particleratebypointspeed.c4d.zip
• 

  Ben Black

  December 11, 2014 at 8:02 pm

  That’s a great help, thanks so much.

  Ben

  cargocollective/benblack

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