Driving Displacements with particles

[TheMightySpud]

Hi all,

Does anyone know how to acheive an effect like raindrops falling into a body of water and those raindrops causing ripples in the water where the rain is made using particles? for example, as the particles die, a ripple displacement is triggered?

Thanks in advance.

TheMightySpud

[JeffrySG]

This video might help:

ftp://ftp.newtek.com/multimedia/movies/w3dw/rainsplash.mov

[TheMightySpud]

Thanks for the reply, but that's not what I'm trying to do, that tutorial deals with 'splashes', I'm trying to figure out the surface of the water rippling everytime a particle impacts on its surface.

TheMightySpud

[Oliver]

This might help:
http://pagesperso-orange.fr/dpont/plugins/textures/RainDrops.html

Or this:
http://pagesperso-orange.fr/dpont/plugins/textures/ParticlePaint.html

Regarding that:
I already said it and I'll say it again -
Almighty Denis - THANK YOU! :bowdown:

Greets.
Oliver.

[Mr Rid]

Hi all,

Does anyone know how to acheive an effect like raindrops falling into a body of water and those raindrops causing ripples in the water where the rain is made using particles? for example, as the particles die, a ripple displacement is triggered?

Thanks in advance.

TheMightySpud

Could create a pre-rendered scene to create an image sequence of ripples to apply as a displace or bump that will synchwith each drop-

Set a child emitter to emit upon erase of the parent 'rain' particles. Each child particle then triggers a sprite with a simple greyscale expanding concentric circle texture. Render from an orthoganal camera looking down on the Y that frames the appropriate area of your water surface. This is to create an image sequence of little ripples to use as a displace or bump to synch up perfectly in your scene of falling raindrops.

[evenflcw]

This might help:
http://pagesperso-orange.fr/dpont/plugins/textures/RainDrops.html

Or this:
http://pagesperso-orange.fr/dpont/plugins/textures/ParticlePaint.html


You can also do it by comparing spot position and particle position... but the image won't stick as with particle paint. Instead you would animate via the particles distance from the spot. Could work for rainsplashes which emerge and disperse but not for paintsplatter which need to layer ontop of eachother.

[pooby]

Unless the raindrops are very few and far between, you wont notice if the ripples are exactly in the right spot, so I'd fake it.

[Mr Rid]

The trick I was describing is similar to this rain example-
http://www.box.net/shared/static/jmva79u42c.mov
scene zip-
http://www.newtek.com/forums/attachment.php?attachmentid=52807&d=1196815806

And a bullets example-
http://www.box.net/shared/static/tb60fd3ms8.mov
http://www.box.net/shared/static/bag66ve9wk.mov

[Mr Rid]

Doh, that last link was suppose to be this-
http://www.box.net/shared/static/49uzw2uucs.mov

[faulknermano]

mr rid, what's going on with the bullets example? in the bag66ve8wk.mov you've got particles impacting the object. is the dynamic movement of the debris set off on Event?

[Mr Rid]

mr rid, what's going on with the bullets example? in the bag66ve8wk.mov you've got particles impacting the object. is the dynamic movement of the debris set off on Event?

No, I didnt mean to post that link but rather the one in the following post. But I was using a similar image sequence generated like this- http://www.box.net/shared/static/tb60fd3ms8.mov pre-rendered from an orthoganal camera perspective and then used as a displacement map on a mesh unseen by camera and set to collide in order to punch out the pieces of the wall object. It doesnt work too well because of the lack of subframe calculation in LW dynamics. Most of the pieces just drop straight down instead of getting knocked away. For that collision example, I actually enveloped a dissolve on the sprites to appear over 3 frames to ease in the collisions a bit, but it didnt help much.

Without subframe calculation, a rapidly moving collision object can pass thru the target object in one frame and little or no reaction occurs.

[Mr Rid]

I reloaded that scene and in attempt to make a new preview that shows the displacement collision more clearly and actually ran into a new bug, and some old ones.
http://www.box.net/shared/static/14via1iww0.mov

You see the bullet particles are erasing, triggering the white child sprites which create the original image sequence that was pre-rendered to displace the mesh seen in wireframe. But because of the lack of subframe calc, the parent erase, the child emit, and the debris particles are all occuring 20cm after the collision plane. I compensated by just moving the collision plane forward 20cm, but here I left it in place to demonstrate the problem. If it were an irregularly shaped object I suppose you would have to smooth shift in Modeler to create an appropriate collision object.

But this scene is at 100fps. Originally it was at 240 fps, but I had just noticed there was something odd going on with the playback of the baked Hard FX pieces. With playback at 100%, the motion was mysteriously frozen every second to third frame- the pieces moved/updated 2 frames, then 2, then 3, then 2, etc. After recalculating, even at 120 fps I was still getting a skip on very 10th frame. I had to turn the fps down to 100 before the frame skipping completely disappeared from hardFX calculation. PFX does not have the same error with higher than normal fps.

----------------------

This scene raised some other problems I will now gripe about.

I tried to offset the start frames for all baked PFX and BDD motions to compensate for the change in frame speed from 240 to 100fps... I dont know why the hell there isnt just a simple 'START FRAME' value instead of that stupid Key option where baked motions must start from a keyframe. This is a conflict when you want to actually keyframe the baked item separately from changing the start frame. MDD plug offers an option for a start frame, but for some odd reason it is in seconds instead of frames. WHY? Just one of the many little incoherent functions in LW's interface- similar functions work differently in different windows or menus for no apparent reason (like 'Replace' instead of 'Load' in the Graph Editor but nowhere else, which doesnt make sense when 'Paste' would also be a 'Replace').

So you have to figure out how many negative frames back to put a keyframe in order to have a motion start on the frame you want and delete all other motions or parenting. I want to conveniently use the graph editor to slide the frame back until it looks right, but a single key at 0 or before will not show up for some other buggy reason. Whats the deal here?

I give up and decide to clear all the motions. And then another bug occurs where the motion is still controlled by the start Key frame until I either reload the scene or make a new key at 0 for each PFX or HardFX item.

Now I just need to offset my image sequence to a negative frame... gee, another bug. Cant set negative start frames for image sequences.

Calculation is a little slow, and I really only need to calculate from frame 87 on... but there is no option to tell calculation which frame to start on. Changing the global start frame has no effect as it does with Preview, or like it does for the global End frame... another incoherency. And I keep wondering why ESC key does not logically abort calculations like it does for previews, renders, and processes in most other programs? Another annoying little incoherency.

[HowardM]

heheh come to the dark side Rid, try Maya and be free of most of these issues ;)

i agree, all these little inconsistencies and bugs are pretty lame and a result of programmers (NOT ARTISTS) testing (if they even do) the software...

how hard is it to sit down and PLAN things out and execute them the right way... NT need to hire people like you and I, who have pushed every FX button for years, and let us show them the way....

ah well, we either have to live with the way it is, do the workarounds, or move on...

I still miss the hell outta LW though :)

[Mr Rid]

...

i agree, all these little inconsistencies and bugs are pretty lame and a result of programmers (NOT ARTISTS) testing (if they even do) the software...

Its as if different people worked on different aspects of the program or at different times and each implemented their own approach. Some stuff originates as a 3rd party thing and odd terms and buttons spill over.

Its frustrating when you may see feature demos or tutorials that are applied to something very simple (bouncing ball or somesuch). But when you attempt something a little more complex or for a very specific project demand, the rickety house of cards is exposed. But the real frustration is when I am only trying to do something this simple and unspecific but still keep bonking into walls.