View Full Version : Locked particles modification

05 May 2011, 07:28 AM
Hi there,

i actually need to modify the geometry (instanced) of particles that are spawned with Object Location, Lock On Emitter enabled.

This for making grass that is being cutting through pass of a mower.
Also the grass is at her first step 30cm high, instanced editable poly, then "something" comes and changes its instanced geometry to another editable poly, 5cm high.
I tried with a deflector, a group selection, a group operator, a selection test to send the selected particles to the next event with another geometry... nothing works.

The problem seems to be that the particles are locked, and can't be selected or modified. When "lock on emitter" is disabled and a little speed given to the particles, they can be selected. But flying grass is pretty amazing...

Has anyone an idea about how to do that ? I think about scripting but... it's scripting, though.
Well if someone could help me, thanks a lot !


05 May 2011, 01:48 PM
Well, i've found.

I had to put a Group Selection, select the particles that are in the icon (p.e. cube), then a Split Group and send this result to the second event with no modification but the instanced shape.
I had problems with the position of particles (this one was randomized cause of the rotation set as random horizontal with 180 divergence, but divergence is useless if random...).
Now it's ok, and the animation of the Group Selection Icon is possible (and efficient).


05 May 2011, 01:00 AM
I am not sure if i follow you a 100% but it seams you didn't reset XForms before using the geo as shape instance maybe?

i made a grass tutorial a while back over at evermotion:

maybe that helps?

kind regards,

I attached a super quick setup that cuts the gras short and maintains the rotation/position, just switches out teh shape instance with a shorter version. Max2010-64bit file, no plugins needed.

05 May 2011, 02:14 PM

thanks for your answer, but i found the right way yesterday.

I had to put an group selection (inside a moving icon), and a Split Group to send the selected particles to the next event with another instanced geometry.

I had a problem with randomized rotation / position but i've corrected them as i deactivated the random position in the second event, and put divergence to 0 in the first (with random horizontal position).

Well, nice tutorial, though :)
i'll use it the next time i have to make grass !

05 May 2011, 02:43 PM
Glad I could help :)


05 May 2011, 05:55 AM
Zortek, it sound interesting on what you doing there. Can post the result and description on how to do it?


05 May 2011, 09:46 AM
Of course i can !

I attach some pictures to my post : the particle view, and different steps of moving the icon of the Group Selection (not the result of my work, because of a private job).

Particles are locked on a plane, with the speed disabled (because useless in my example).
In this configuration, the second event only changes the shape of the particles. No moving, no rotating or scaling. U can also use Shape instance with different instanced gometry each event.
Some other parameters of the Selection Group can be used (random, inside an object, etc).
Fo my project I attached the icon to a dummy which moves, easyer keyable.

happy to be helpful :)

05 May 2011, 05:56 AM
Thanks bro! Learning new thing everyday. Was into particle lately.

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