Problem (Particles)

[Omy]

Hi everyone,

Im a beginner to Houdini,I am creating a meteor effect.I want the trail size of the meteor to die as soon as it hits the ground.Please help me.I have uploaded my work file

Sincerely,

Om Kapoor

[Omy]

met8doubt.hipnc

[DeehrBYU]

Here's a really simple solution. I didn't take time to tweak it to make it look great. But anyway, I first created a name on the birth group on your "source" node in the popnet. (Called initial). Then I created a sphere that is keyframed to move down the trail. (killtrail_sphere) Then, at the end of your POPNET, i created a collision with the sphere and the group "initial" in order for them to die on contact. So there is just one way you could do it. However, to make things more natural, it would be nice to have them blow away rather than just have the trail shrink. For example, Using the sphere or any other primitive to create a new group, you could make a force on just that group. Hope that helped a little.

met8doubt_trailKill.hipnc

Edited June 6, 2010 by DeehrBYU

[Omy]

Here's a really simple solution. I didn't take time to tweak it to make it look great. But anyway, I first created a name on the birth group on your "source" node in the popnet. (Called initial). Then I created a sphere that is keyframed to move down the trail. (killtrail_sphere) Then, at the end of your POPNET, i created a collision with the sphere and the group "initial" in order for them to die on contact. So there is just one way you could do it. However, to make things more natural, it would be nice to have them blow away rather than just have the trail shrink. For example, Using the sphere or any other primitive to create a new group, you could make a force on just that group. Hope that helped a little.

That was a clever way of doing that..Found a new trick! However i dint understand the second method,U mean to select the particles and adding the force? can u give an example file to show that

Sincerely,

Om Kapoor

[DeehrBYU]

Haha, it is actually a really common solution. Here is the file you requested about the groups. When working with many things, groups are INVALUABLE. Learn to use them well! In this example, the node "affect particles" is a group node that is using "Killtrail_sphere" to create a new group called "BlowAway" once the sphere touches the particles. If you want to see if your group is working, you can middle mouse on the node after it, and it will say something like "4335 points in BlowAway." Then, you can create a force POP and tell that force to only affect the "BlowAway" group. Does that make sense?

met8doubt_bloqAway.hipnc

[DeehrBYU]

Just for the sake of clarity, I created this example. It might help you understand better since there are less elements in the scene. Using the two spheres, I am creating two groups "Blow_right" and "Blow_down." With these groups, you can apply specific forces to only the particles that are in that group. You can see on the second sphere, the particles that don't touch it continue on, while the ones that hit the sphere go downwards. As you can see there are limitless opportunities with groups!

Let me know if you have any questions.

better_example.hipnc

Edited June 6, 2010 by DeehrBYU

[Omy]

Just for the sake of clarity, I created this example. It might help you understand better since there are less elements in the scene. Using the two spheres, I am creating two groups "Blow_right" and "Blow_down." With these groups, you can apply specific forces to only the particles that are in that group. You can see on the second sphere, the particles that don't touch it continue on, while the ones that hit the sphere go downwards. As you can see there are limitless opportunities with groups!

Let me know if you have any questions.

awesome.The second example was very clear and made me understand the concept.

Many thanks.

[Omy]

Hi,

I have one more question,Suppose if i make it as a digital asset.Can i make the things happening dynamic way.For example if an user wants to choose the meteor to hit the grid at frame number 50.

The behaviour should be the same.I mean the killtrailsphere should also dynamically change.Is it possible?

Let me know

Sincerely,

Om Kapoor

[DeehrBYU]

Yes, Im sure it would be possible with expressions. Would take some clever thinking...I cant think of a way exactly how you would do it right now, but if I have something come to me, ill make an example. Ill think about it a little today. There are also many people who know houdini 1000 times better than me so maybe they could help you out too.

[Omy]

I have one more doubt also,

Now that if i want to activate the particles to start their action at a frame where user wants from a digital asset,can we set a global variable or something and make it as a relative reference in the constant activation

for eg

$F > 36

would allow us to start the action from frame number 36,

can this be set as dynamic

Please give me your opinion guys

Many Thanks