Rotation For Instancer

[yoshsoy]

Hi,
I created particle instancer and wrote expression for the instancer rotation through custom attribute in the Per Particle(Array) Attributes. Then I plugged it in the Rotation drop down menu under the Instancer(Geometry Replacement) but it's not working. I didn't get any error when I created expression. I was able to get custom scale attribute to work fine. Do you guys have any idea about it? This is Maya 7. thanks

[gunbird]

err..., what's effect do you want to achieve?

[yoshsoy]

I am watching Gnomon Dynamics7 DVD and was trying to make explosion with one boulder applied to Instancer. As it explodes those randomly scaled and oriented boulders by expressions are emitted from the emitter and are supposed to randomly spin over the time but they are not spinning. Here's the expression for Creation,

float $foo = rand(.2,1);
particleShape1.custom_scale = <>;

particleShape1.random_number = rand(-.01,.01);
particleShape1.custom_rotation = <>;

and for Runtime,

particleShape1.custom_rotation += particleShape1.random_number;

Then I mapped the new attributes to the correspoing attributes under the Instancer folder. The random scale and orientation at birth are fine but they don't spin. What am I missing???

[gunbird]

I speculate the rotation just sets the orientation of the instanced objects relative to their initial orientation, so at runtime this value is unchangeable.
A simple method to make them rotate is rotate the original geometry.
That's say base on your setting, add expression for geometry RotateX(YZ) related with time or frame.

[yoshsoy]

Thank you, I added expessions for the geometry's Rotate X,Y,and Z and it works, but they don't look natural due to the same spinning each one has. How can I make them spin ramdomly? That's what I'm going for.

This is strange. I followed exactly the same step as Alex did in the DVD and saw his instancers rotate but not mine. I also tried the instancer Maya file that came with the DVD and they are not spinning.

[gwelch]

This simple technique works for me:
Creation expression:
particleShape.gbw_rotate = <>;

Runtime expression:
particleShape.gbw_rotate = (particleShape.gbw_rotate +10);

QUOTE(yoshsoy @ 10/08/06, 01:07 PM) [snapback]249495[/snapback]
Thank you, I added expessions for the geometry's Rotate X,Y,and Z and it works, but they don't look natural due to the same spinning each one has. How can I make them spin ramdomly? That's what I'm going for.

This is strange. I followed exactly the same step as Alex did in the DVD and saw his instancers rotate but not mine. I also tried the instancer Maya file that came with the DVD and they are not spinning.

[gunbird]

Hi yoshsoy,

sorry I said "I speculate the rotation just sets the orientation of the instanced objects relative to their initial orientation, so at runtime this value is unchangeable." is wrong!

I check your expression again, and it do work properly. I suppose you can't see the rotation is for the random_number too small. Give it a large range , eg. -5~5, and try again.

[yoshsoy]

The issues was solved! I tried both of you guys technique and it works fine now. I appreciate it.

[adam-clear]

QUOTE
float $foo = rand(.2,1);
particleShape1.custom_scale = <>;

particleShape1.random_number = rand(-25,25);
particleShape1.custom_rotation = <>;

and for Runtime,

particleShape1.custom_rotation += particleShape1.random_number;

For those of you who don't know...(This was me. I had to ask.)...link the custom_scale per particle vector to the scale attribute and custom_rotation per particle vector to the rotation in the particleShape1 Instancer tab. The random_number is only used in the runtime expression. Also, I increased the random_number per particle float quite a bit to get some faster spin.

As for runtime, I entered it for runtime after dynamics (I'm on Maya 8).

I hope this helps the particle newbies.