Particles - Wind Blowing Effect & Particle Build-Up

[ggoblin]

A side question: What doesn it mean to "use baked physics" ?

Baked, in this context, means Moho will create a keyframe at every frame of the affected objects. This is so you can safely turn off Physics and keep the result, and frees Moho from constantly calculating the physics.

Thank you for the swift response. Thats interesting, I will investigate.

[ggoblin]

Only animated properties (those with keyframes) are referenced.

Thanks Wes. Thats an important nugget to remember.

I thought physics settings were animatable? I remember seeing the atom icon on the timeline lol. Are only some animation properties animatable?

[synthsin75]

Only animated properties (those with keyframes) are referenced.

Thanks Wes. Thats an important nugget to remember.

I thought physics settings were animatable? I remember seeing the atom icon on the timeline lol. Are only some animation properties animatable?

Well, if I remember correcting, the settings of the physics simulation are animatable, but not the properties of individual physics objects. Like, a stationary object cannot become a moving physics object.

[Greenlaw]

Update: I looked up baked physics in Moho and it's not exactly as I described it. Here's the description from the manual:

Use baked physics (advanced): Turn this option on to stop the physics simulation from running. It will play back results from the last time you played back the animation.

Normally, physics simulations are re-run every time you play back an animation so that they can respond to other objects in the scene. The advantages to using baked physics are (1) it is faster to re-use simulations rather than to re-run the physics; (2) If the physics simulation doesn’t give you the results you want, you need to tweak results. You can’t manually animate objects if they are under the influence of physics, but you can use the precomputed physics while you modify keyframes as you see fit. (3) If you get a result that you like, you can turn this option on to make sure it doesn’t change.

So I was close: enabling this stops Moho from continuously calculating and uses the keyframed data only. My description was inaccurate where I said enabling it creates the keyframes, but the keyframes are created by Physics regardless of this setting.

I guess it doesn't really matter in practice but I didn't want to confuse matters.

[SuperSGL]

Thank you SuperSGL, thats a very innovative approach. I tested it both with and without a force field with interesting results. Left is with force field (light blue layer), whilst right only has the dark blue non-moving object. In both the particles have maximum friction (5) and maximum density (100) to minimize bouncing. As you can see in this example both work ok, but I think that is down to luck of the draw. As you point out in his example of the window ledges, if you remove the force field is causes some issues with a few particles jumping.

Your welcome. I know what I want to say but don't always make that very clear I'm just glad someone understood what I was trying to explain (All though I did feel better when I found the file )

[ggoblin]

Here is my very terrible attempt of using physics to gather leaves.. I think its best if I wait for the pros to show me how its done



The file is a bit big, so it will stutter the first time its played until its in your browser cache.

[ggoblin]

Update: I looked up baked physics in Moho and it's not exactly as I described it. Here's the description from the manual:

Use baked physics (advanced): Turn this option on to stop the physics simulation from running. It will play back results from the last time you played back the animation.

Normally, physics simulations are re-run every time you play back an animation so that they can respond to other objects in the scene. The advantages to using baked physics are (1) it is faster to re-use simulations rather than to re-run the physics; (2) If the physics simulation doesn’t give you the results you want, you need to tweak results. You can’t manually animate objects if they are under the influence of physics, but you can use the precomputed physics while you modify keyframes as you see fit. (3) If you get a result that you like, you can turn this option on to make sure it doesn’t change.

So I was close: enabling this stops Moho from continuously calculating and uses the keyframed data only. My description was inaccurate where I said enabling it creates the keyframes, but the keyframes are created by Physics regardless of this setting.

I guess it doesn't really matter in practice but I didn't want to confuse matters.

Thank you for the exlaination. When the physics engine is running it takes control of certain channels - translation and rotation, so we are locked out from changing them. I noticed when I 'bake' the physics I dont have that restriction.. I'm guessing this allows us to add additional influences on the objects to move them exactly how we need?

[ggoblin]

Only animated properties (those with keyframes) are referenced.

Thanks Wes. Thats an important nugget to remember.

I thought physics settings were animatable? I remember seeing the atom icon on the timeline lol. Are only some animation properties animatable?

Well, if I remember correcting, the settings of the physics simulation are animatable, but not the properties of individual physics objects. Like, a stationary object cannot become a moving physics object.

Thank you Wes!

Thinking aloud, if we want to use Physics to control lots of objects, for example leaves, then it makes sense to use a script to generate these objects as we would want each of them with slightly different physics properies eg initail direction, initial speed, etc ? I see there is a MohoPhysicsOptions class in the API..might investigate if I get the time

[ggoblin]

Thank you SuperSGL, thats a very innovative approach. I tested it both with and without a force field with interesting results. Left is with force field (light blue layer), whilst right only has the dark blue non-moving object. In both the particles have maximum friction (5) and maximum density (100) to minimize bouncing. As you can see in this example both work ok, but I think that is down to luck of the draw. As you point out in his example of the window ledges, if you remove the force field is causes some issues with a few particles jumping.

Your welcome. I know what I want to say but don't always make that very clear I'm just glad someone understood what I was trying to explain (All though I did feel better when I found the file )

Your explaination was very clear and the information very useful - I had not heard of force fields in Moho before .. it certainly intrigued me . (the only encounter I had with physics engine before was Victors billiant tortoise tutorial which didn't use force fields).

[pihms]

Found the file if you register at animestudiotutorial you can download it and check it out, here is the link https://www.animestudiotutor.com/shared_files?id=446

edit: Just checked it out more the ledge open rectangle catches the snow and the rectangle uses force 'field on' I took that out of the folder to see what it would do and the snow started bouncing around and some would pop out. The force field on the rectangle made them stick to the ledge with no movements afterwards.

Thank you SuperSGL, thats a very innovative approach. I tested it both with and without a force field with interesting results. Left is with force field (light blue layer), whilst right only has the dark blue non-moving object. In both the particles have maximum friction (5) and maximum density (100) to minimize bouncing. As you can see in this example both work ok, but I think that is down to luck of the draw. As you point out in his example of the window ledges, if you remove the force field is causes some issues with a few particles jumping.



As a side note I used 70 particles, one original and the rest references to it. I thought this way if I adjust physics properties of the original it would automatically adjust the references for me.. but that doesn't seem to happen. Not sure why... all the references particles still have blue arrows indicating the reference isn't broken.

A side question: What doesn it mean to "use baked physics" ?

I like how this can be applied so well to snow, leaves, and other objects that need to be stable after a drop. Another good technique to apply with the others presented. Thanks!

[SuperSGL]

If you can't get rid of the glitches you might be able to hide it some what with another set of leaves blowing across using particles. They'll have to float off screen but you could animate the particles to finish when the physics stuff is complete.
Did you animate them lying flat on the ground after the bake?

[ggoblin]

If you can't get rid of the glitches you might be able to hide it some what with another set of leaves blowing across using particles. They'll have to float off screen but you could animate the particles to finish when the physics stuff is complete.
Did you animate them lying flat on the ground after the bake?

No I didn't use the bake - being an experiment, I wanted to see what could be accomplished via the physics engine without any touch ups. Touch up would definitenly have started with that last annoying leaf just stationary in the air before finally settling down lol .

I did include secondary motion of the leaves that changes their orientation as they approach the ground.

Slightly less glitches in this version: ( I removed the cycles in the secondary motion of the leaves)

[ggoblin]

To clarify, physics engine takes control of layer translation (x,y and z) and z-rotation, so we still control x-rotation and y-rotation of the leaves - I use them for the landing re-orientation.

I think the glitches in the air are due to my secondary motion, will investigate.

[pihms]

For accumulation, try having the moving particle feed into an accumulating particle doing something like this:


Not much control over the speed of accumulation though.

Thats an interesting approach Wes.

I tested that with the two particle players - one normal particle layer at top showering down particles, and a second particle layer at the bottom of the screen set to 'gather' particles. This was set not to be at full speed at start so we could see a build up, but as you said there is no real control of the speed of the build up. Damping was set to maximum, velocity and acceleration to 0, to ensure particles do not move about.

I'm having difficulty getting the force field settings to apply the way I want, something to experiment with, but this method could work very well, using a mask at the base of the first layer to hide once they hit the ground point.

[Greenlaw]

Sorry I took so long getting back to this test. Anyway, here's the physics/particles cheat idea I was thinking about...



This uses Physics for the falling leaves that rest on the ground. The cheat part is that I'm also using Particles to fill out the leaves because I'm only using about 20 leaves in the Physics part.

TBH, if I were doing this for real, I'm more likely to do this using a 3D program or maybe Trapcode Particluar in Ae. Moho's particles and physics engine is too limited to do this the way I'd like...but trying this in Moho was an interesting challenge.

Here's the project file if anybody wants to pick it apart...

fallingLeavesA.moho