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Author Topic: Scattering on animated surface  (Read 4133 times)


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Scattering on animated surface
« on: February 26, 2015, 04:19:28 PM »
Hey this might have been asked before, but the other threads i have read haven't had any solution tho this.

attached here i have a little video file where you can see how the scattered objects spawn/despawn and glides around on the animated surface.
My goal is to scatter these objects on frame 0, then lock em to the animated mesh so they follow it for the duration of the animation.

View My Video

PS: the preview is short so if you can i recommend playing it with ping pong to see the sliding clearly.

we are using forestpack pro 4.2.5
3ds max 2014
windows 7 x64

any ideas?
« Last Edit: February 26, 2015, 04:23:02 PM by Stir »


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Re: Scattering on animated surface
« Reply #1 on: February 26, 2015, 07:39:49 PM »
i think somehow you need to lock number of scattered items
now as surface deforms - density is trying to stay constant (and here is the issue for you)

but have no idea how to deal with that...


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Re: Scattering on animated surface
« Reply #2 on: February 26, 2015, 08:49:58 PM »
Your totaly right, there must be something like that going on.
But as far as i know there is no way to tell forest on what terms you want to scatter, if its based on numbers, density or area. Only options i know of is UV and XY.

ey itoo... make that lock number button :D hehe

Michal Karmazín

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Re: Scattering on animated surface
« Reply #3 on: February 27, 2015, 05:30:57 PM »

Yes, it's possible to avoid these troubles, while dealing with deformed UV space in time, with a help of Particle Flow. This way you can define the total number of simple "help" surfaces, which can be later used to scatter with Forest Pack in UV mode.

You'll need to create a PF Source object and in the Particle View window adjust the Event as on attached screenshot. In Birth operator under Amount, you can define the total number of "help surfaces" - also I recommend to set the Emit Start & Emit Stop to -1. Than you should add a Position Object operator and assign your object as Emitter Object. You should mark Lock On Emitter and Animated Shape options to follow the deformation. To rotate normals accordingly add the Speed by Surface operator, select Control Speed Continuously and mark Animated Shape, the used Direction should be set to Surface Normals. In Shape operator I recommend to use simple 2D Triangle. The Rotation operator should use Speed Space and Y axis should use value of 90. Now the Particle Flow object should be set up properly to follow your animation.

As actually Forest Pack can't use directly the FP Source object as a valid mesh, this needs to be generated with a help of Mesher object (as shown on this related post). Create a Mesher object (Compound Objects - Mesher) and pick the previously set up PF Source object. The Mesher object than should be mapped with UVW Map modifier with Face Mapping selected.

Now you can create the Forest object and use the Mesher object as a Surface in UV mode. If needed, the Density can be adjusted to get desired number (one) of item(s) for each "help surface". The Update surface data automatically option needs the be marked to follow the movement.

Attaching simple scene with this workflow used. Hope that helps.

Kind regards,
« Last Edit: February 27, 2015, 05:56:15 PM by iToo »


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Re: Scattering on animated surface
« Reply #4 on: February 28, 2015, 04:59:11 PM »
Thanks for the workaround!
To bad there is no easier way to achieve this.

When we already are innside PF, we might as well just use that for scattering and animation and just bypass Forest Pack all together.
I prefer to use Forest Pack when i can, because its fast and easy to setup.

Thanks for the help with the issue :)