Question

I am trying to create an animation for lemon juice and baking soda experiment, and I was wondering how can I create a foaming effect such as the one shown in this image:

The idea I have in mind is to simply draw a foam in photoshop and then use motion tween to change the size. I was hoping I could find a better solution to this.

Answer 1

I have something somewhat similar that you can probably use as a springboard for doing your own thing.

http://www.shaunhusain.com/SteamEffect/

http://www.shaunhusain.com/SteamEffect/srcview/index.html

Currently I’m just drawing some circles with this and then setting a blur on them (not very efficient I know but it served the purposed as I didn’t need it to create a bajillion particles to still be effective as “steam” which was the intended goal). You could swap out the shapes/filter I’m using for your own drawing and use the same basic structure.

EDIT

Perhaps this requires at least a little explanation:

Basically you’d want to look at the two files SteamCanvas.mxml and BitOfSteam.as. To be honest I have no idea why I decided to write SteamCanvas as an mxml file. I chose to use Canvas as the base class so I could just wrap it around any other component as a container and be able to detect mouse clicks anywhere within a region. If this is being used in a pure Flash environment, that is one not using the Flex libraries (or mxmlc compiler) it could be changed to extend from Sprite and be written purely in AS3, essentially just the creationComplete code should be moved to the constructor. How this works is the SteamCanvas is a wrapper for whatever controls or components you want to put in it (just like a normal canvas uses absolute positioning, but could have containers that define layout nested within it if need be). The SteamCanvas sets up a timer and if the mouse is down when the timer ticks, it creates instances of BitOfSteam and sets the properties for the steam based on the SteamCanvases own currently set properties. In the project you’ll also see a SteamEffectTest.mxml which is just the file you see running that has the sliders on it to change the properties of the SteamCanvas, I used these to come up with what I thought were good values to make somewhat realistic steam. If I remember I’ll revisit this component tomorrow and try to take Marty’s suggestions to get it updated.