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wayward particle spray
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wayward particle spray // Archive: Tech Forum
Post by Burnart // Nov 7, 2006, 11:49am
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Burnart
Total Posts: 839
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My next problem! This time with true particles in tS 6.6 - playback in tS 7.1 shows the same result.
I've set up an emitter which has 5 key frames. The only change is a phased reduction in the number of particles emitted per frame. All the starting conditions were entered into the truparticles requester and tabs on frame zero, the "make constant" button was deselected and then the first keyframe was set. The other keyframes were moved to and set in order - ie frame 25, frame 50, frame 100 etc. I have bounce and gravity helper options selected. These are not changed at any of the keyframes.
When I play the animation the particles fall through the selected bounce object and bounce off a "ghost"of it instead! If you look at the pic, the blue object is transparent and you can clearly see the particles spreading out in the correct way but inside the object rather than on its top surface!
Can anyone tell me what is going on? - better still, can anyone tell me how to solve it? |
Post by Bobbins // Nov 7, 2006, 12:37pm
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Bobbins
Total Posts: 506
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Not sure, but can you check the position of the axis for the bounce object? Is it in the centre of the object or is it somewhere else like at the base? |
Post by spacekdet // Nov 7, 2006, 2:47pm
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spacekdet
Total Posts: 1360
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Where is the ground plane in relation to the ghost bounce? |
Post by Burnart // Nov 7, 2006, 11:04pm
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Burnart
Total Posts: 839
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The attached pic should answer your questions. To the best of my memory I think the object was put in position and squashed before I set the first key frame but I'm not 100% sure. The axis is in the objects centre.
What else can I tell you - I tried moving the object out of the way and the particles fell straight down as you would expect. If I create an emitter with the same start conditions then select the "Make constant" button the particles bounce off the object in the correct fashion.
Suggestions anyone? |
Post by TomG // Nov 8, 2006, 3:23am
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TomG
Total Posts: 3397
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My first thought is to test whether this is an offset, or a static thing - what happens when you move the object, does the "actual deflector location" move with it, or stay static? Is it always offset by the same amount?
What happens if you remove the deflector, maybe even recreate the object, and try again? What happens if you use another object in place of that one, a different primitive or shape though, the same thing?
The results to those tests may give some pointers as to what is happening :)
HTH!
Tom |
Post by Bobbins // Nov 8, 2006, 9:54am
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Bobbins
Total Posts: 506
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I've just tried recreating this in tS6.6. I set up the scene as best I could given your screen shots, description and some sensible guesses. It works all the time for me - the particles correctly bounce off the reflector object. Can you reproduce this if you set up your scene again? |
Post by Bobbins // Nov 8, 2006, 10:03am
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Bobbins
Total Posts: 506
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Update - I can reproduce this by 'cheating' and not using the particles helpers to achieve the animation:
If I set up the emitter to use tS physics, run a physical simulation, move the emitter down or the reflector object up on frame 0, keyframe the move then play back the animation then of course the particles bounce too low down, but that's to be expected and correct. I'd need to re-run a physical sim to make the particles bounce off the reflector object again. |
Post by Burnart // Nov 8, 2006, 12:13pm
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Burnart
Total Posts: 839
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I didn't come to the forum on the basis of it going wrong the first time - I have invested a number of hours trying to solve this myself before setting up the scene shown in a very controlled fashion. In my previous experiments I have tried different objects (some simple as above and some with greater mesh complexity) and I got the same result - that is, the particles fell through the object and spread out rather than spread out on the surface. If I move the object downwards the offset of the particles moves with the object.
Bobbins are you sure you are testing an emitter which is changing particles over time? I have no problems when the item has the make constant button selected, problems only occur when I deselect that option and try to animate the particle motion options over time. I'll post the scene if it helps - but currently I'm at work so I'll have to do it this evening. |
Post by Bobbins // Nov 8, 2006, 12:55pm
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Bobbins
Total Posts: 506
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Yep, I set it up so the emitter changed particles over time. I keyed a change at frame 0 and frame 100 and it worked consistently. I'm also not in the habit of posting to the forum unless I know what I'm talking about and am sure of what I've done, thanks.
Having said that I've just gone back and tried again with an intermediate emitter change at frame 50 and it failed like you saw, so a few more tries makes it appear that a linear change works but an interpolated change causes a problem.
Looking in the Scene Editor I can see 'move' keyframes for the particle emitter. They only appear when I make a change to the emitter and record a keyframe. Deleting those move keys keeps the emitter changes intact but then allows the particles to bounce off the reflector object properly again. Take your scene and delete the move keys for the emitter in the Scene Editor and see if it works for you too. |
Post by Burnart // Nov 8, 2006, 1:14pm
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Burnart
Total Posts: 839
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Thanks Bobbins. To get it in a nut shell - is what you are saying that ONLY the first and last positions of the animation should be keyframed? (I'm a bit vaguer on whether setting positions in the trueparticles requester at different frames has any effect if not officially keyframed - subject of my next experiment.):)
I shall update my manual with some hand written comments - ie. important stuff that actually ensures the process works! |
Post by Bobbins // Nov 8, 2006, 1:28pm
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Bobbins
Total Posts: 506
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I keyframed all the emitter changes by hitting the tS record icon. When I just had a start and end keyframe (frames 0 and 100 for my test) it was OK. It was only when I went back and keyed a change in the middle (anywhere between 0 and 100) that it started going wrong. In the Scene Editor, I deleted all the 'move' keys for the emitter at every keyframe (therefore removing the 'move' track for the emittor object) and it then worked OK on playback. |
Post by Burnart // Nov 8, 2006, 4:47pm
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Burnart
Total Posts: 839
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Ok - remove the "move" keyframes! Gotcha - I'll give it a whirl. Thanks.
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Its the next day and I'm just appending a little to my last post. Yes it worked the particles do now scatter across the object!! Now I can return to the project I was actually investigating this problem for. |
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