In the Creep U channel could you put in something like:
0.5 - $ID/20
And then animate the 0.5 value somehow? That way they would spread out along the curve up to the halfway point and offset back by thier particle ID…
But you cant animate a single parameter in an expression…. How is that done, do you add an attribute, animate that and then use it in the expression?
…
I just tried that, it seems to work….
See attached.
Moving particles along a path?
35854 26 3
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- Mike_RB
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- Mike_RB
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- stevecullum
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As I continue to explore the various ways to achieve things in Houdini, I'm now trying to recreate this object belt particle effect without using particles!
I have the following expression driving a creep SOP node:
ch(“../xform1/rz”)*0.05/60
It references its motion from a spinning tube so every 60 degrees it moves the objects on the creep by the distance the objects are spaced. What I would like to do is say “everytime the creepSOPS tx channel reaches 0.05, reset tx back to 0 and restart the cycle” thus giving the illusion of a continuous supply of bullets.
I tried an if(ch(“../tx”)>0.05, 0, ch(“../xform1/rz”)*0.05/60) but it fails. I think I know why it fails, but what would I need to do to make this work as intended?
I have the following expression driving a creep SOP node:
ch(“../xform1/rz”)*0.05/60
It references its motion from a spinning tube so every 60 degrees it moves the objects on the creep by the distance the objects are spaced. What I would like to do is say “everytime the creepSOPS tx channel reaches 0.05, reset tx back to 0 and restart the cycle” thus giving the illusion of a continuous supply of bullets.
I tried an if(ch(“../tx”)>0.05, 0, ch(“../xform1/rz”)*0.05/60) but it fails. I think I know why it fails, but what would I need to do to make this work as intended?
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- Mike_RB
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- keyframe
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Wont that cause havok with motionblur? Wouldn't it be better to have something the asks what position a copy is at and deletes it if it reaches the end.
That would also create havok with MB (at least with deformation blur). changing the point count by adding or removing points usually does.
Mind you, that doesn't mean that you can't do MB, you just have to take a few extra steps to ensure that points are added or deleted in the interval BETWEEN the last_segment_end sample, and next_segment_begin sample.
In other words, if you have a 0.1 shutter speed, with frame centered blur, at 3 geo samples, you'll be sampling the geo at $F-0.05, $F, and $F+0.05 – if you ensure that you points are added on the interval, you should be good.
Of course, that does take some babysitting on your part.
Cheers,
Gene
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- stevecullum
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Doh! - I hadn't considered the MB part. :roll: - and its good point! I tend to use Reelsmart for adding Mblur, so wasn't thinking about it.
Ok so I fixed up this version which is now doing as I hoped and won't mess up any motion blur.
The thing is now though, if I middle mouse over the delete node, it says more and more objects, so is it actually deleting them?
EDIT: Its the copySOP expression I need to work on!
Ok so I fixed up this version which is now doing as I hoped and won't mess up any motion blur.
The thing is now though, if I middle mouse over the delete node, it says more and more objects, so is it actually deleting them?
EDIT: Its the copySOP expression I need to work on!
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- stevecullum
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