Don't know if I'm approaching this right, but I'm trying to setup an everlasting stream of bullets entering a chamber. The bullets are on a belt, so I thought if I could create a steady flow of particles along a path I could copy the bullet to the particles. But I can't find a way to make a single stream of particles move along a curve.
Anyone got any ideas?
Moving particles along a path?
35818 26 3
-
- stevecullum
- Member
- 112 posts
- Joined: June 2008
- Offline
-
- edward
- Member
- 7717 posts
- Joined: July 2005
- Offline
-
- stevecullum
- Member
- 112 posts
- Joined: June 2008
- Offline
Thanks Edward.
I had tried the creep POP, but the particles were just appearing at the end of the path and not sliding along it. (I used the slide option btw) Seemed a bit uncontrolled.
I used a simple setup to test… particle location, changed the velocity to 1 and removed the spread by zeroing out the controls below it. Attached a creep node and changed to slide. Selected my re-sample sop from the drop down menu. Shoud I have added or changed something else?
I had tried the creep POP, but the particles were just appearing at the end of the path and not sliding along it. (I used the slide option btw) Seemed a bit uncontrolled.
I used a simple setup to test… particle location, changed the velocity to 1 and removed the spread by zeroing out the controls below it. Attached a creep node and changed to slide. Selected my re-sample sop from the drop down menu. Shoud I have added or changed something else?
-
- edward
- Member
- 7717 posts
- Joined: July 2005
- Offline
-
- stevecullum
- Member
- 112 posts
- Joined: June 2008
- Offline
-
- stevecullum
- Member
- 112 posts
- Joined: June 2008
- Offline
I took a look at the examples, but unfortunately the one I wanted to look at doesn't work - I just get an error message.
I've tried again using forces and creep, but again it fails to travel along the path correctly. Maybe a bug?
I've attached the scene file - its most probably pilot error, but maybe you could take a look and point out where I've gone wrong?
Thanks
I've tried again using forces and creep, but again it fails to travel along the path correctly. Maybe a bug?
I've attached the scene file - its most probably pilot error, but maybe you could take a look and point out where I've gone wrong?
Thanks
-
- edward
- Member
- 7717 posts
- Joined: July 2005
- Offline
I think you're misunderstanding what the Creep POP does. It allows you to set the position of the particle explicitly, every frame. So the Drag and Force POPs have no effect. Secondly, you need to tell the Creep POP what u (or v in the case of surfaces) position you want to place the particle every frame. In the attached file, I just modified the $POSUVU expression to ($FF-1)/120 so that it varies linearly from 0 to 1.
-
- stevecullum
- Member
- 112 posts
- Joined: June 2008
- Offline
-
- stevecullum
- Member
- 112 posts
- Joined: June 2008
- Offline
I had a play with your fixed scene and its pretty much what I need. However i need to modify the expression so that every new particle is born from position 0 and then travel up the spline. So think I would need an expression that says:
“If the particle age is 0 then its position on the U is 0 otherwise its position is equal to the frame no/total frames”
I'm still learning the expression functions, so I'm a bit lost on how to write this in the channel box.
Do you think my approach will create the desired effect?
“If the particle age is 0 then its position on the U is 0 otherwise its position is equal to the frame no/total frames”
I'm still learning the expression functions, so I'm a bit lost on how to write this in the channel box.
Do you think my approach will create the desired effect?
-
- edward
- Member
- 7717 posts
- Joined: July 2005
- Offline
Try $AGE/5
-
- stevecullum
- Member
- 112 posts
- Joined: June 2008
- Offline
-
- stevecullum
- Member
- 112 posts
- Joined: June 2008
- Offline
I nearly got everything working thanks to all your help - Cheers!
One last question if I'm allowed
It seems the sweep sop doesn't work with a popnet so I need to use a copy sop to attach geometry to the particles. How do I orient the geometry to align with the motion of the particle normal direction?
One last question if I'm allowed
It seems the sweep sop doesn't work with a popnet so I need to use a copy sop to attach geometry to the particles. How do I orient the geometry to align with the motion of the particle normal direction?
-
- probbins
- Member
- 1145 posts
- Joined: July 2005
- Offline
stevecullum
I nearly got everything working thanks to all your help - Cheers!
One last question if I'm allowed
It seems the sweep sop doesn't work with a popnet so I need to use a copy sop to attach geometry to the particles. How do I orient the geometry to align with the motion of the particle normal direction?
Orient your original geometry primitive along its Z axis, should do the trick.
“gravity is not a force, it is a boundary layer”
“everything is coincident”
“Love; the state of suspended anticipation.”
“everything is coincident”
“Love; the state of suspended anticipation.”
-
- stevecullum
- Member
- 112 posts
- Joined: June 2008
- Offline
-
- eetu
- Member
- 606 posts
- Joined: May 2007
- Offline
This has been most helpful for me regarding alignment issues: http://www.sidefx.com/components/com_forum/files/instancing_273.jpg [sidefx.com]
eetu.
eetu.
-
- edward
- Member
- 7717 posts
- Joined: July 2005
- Offline
-
- stevecullum
- Member
- 112 posts
- Joined: June 2008
- Offline
Thanks for the link eetu!
So should I be copying the original curves tangent values or be using the particles tangents?
I have to confess to being a bit dim with all this. I'm used to clicking a button - ‘follow path’ - I guess with Houdini you actually have to understand whats going on!
ops:
Do I need the attribute tansfer SOP to copy the normal data to the instances?
EDIT: Doh! - only just saw the attachement Edward - thanks!
So should I be copying the original curves tangent values or be using the particles tangents?
I have to confess to being a bit dim with all this. I'm used to clicking a button - ‘follow path’ - I guess with Houdini you actually have to understand whats going on!
ops:Do I need the attribute tansfer SOP to copy the normal data to the instances?
EDIT: Doh! - only just saw the attachement Edward - thanks!
-
- old_school
- Staff
- 2540 posts
- Joined: July 2005
- Offline
I posted a simple example of having particles following a curve inside POPs here:
http://forums.odforce.net/index.php?showtopic=7394&view=findpost&p=49434 [forums.odforce.net]
-jeff
http://forums.odforce.net/index.php?showtopic=7394&view=findpost&p=49434 [forums.odforce.net]
-jeff
There's at least one school like the old school!
-
- stevecullum
- Member
- 112 posts
- Joined: June 2008
- Offline
I've looked at the bullet_curve example file and its doing exactly what i wanted to happen - so thanks for your help again here.
I looked up in the help what primduv does and sadly I dont understand the explanation. I need to somehow wrap my head around this kind of stuff, so in the future when another issue presents itself I know what I'm supposed to be typing into these channels!
Is there anywhere I can get an idiots guide to Houdini expressions?!!
I looked up in the help what primduv does and sadly I dont understand the explanation. I need to somehow wrap my head around this kind of stuff, so in the future when another issue presents itself I know what I'm supposed to be typing into these channels!
Is there anywhere I can get an idiots guide to Houdini expressions?!!
-
- Mike_RB
- Member
- 78 posts
- Joined: April 2008
- Offline
-
- Quick Links