6 Replies Latest reply on Jul 11, 2009 5:25 AM by Mylenium

    Eliminate problem particles?

    voxL Level 1

      I have an animation where I am using particle playground to send particles down a curved tube - to represents plateletes in an artery.

      I have a mask to contain the flow.  The mask is animated to make a narrowing in the artery and the particles follow it pretty well.  I have a gradient to speed them up as they go thru the narrowing.  However, as the narrowing gets smaller, some of the particles start bouncing up and down rather than going thru.  Is there a way to prevent that?  Maybe an expression which would delete them if their movement in X is below a threshold?

      Thanks.

        • 1. Re: Eliminate problem particles?
          Mylenium Most Valuable Participant

          Well, you will have to create property maps. Since you already have mask shapes, it should be easy enough to apply a stroke effect, blur the result and use it as a map for the X and Y velocity, visibility, life or whatever you fancy. Probably you will want to do that as ephemeral maps, so the speed can pick up again after the narrow passage and the modifications really only occur while the particles are travelling across non-zero areas on the map...

           

          Mylenium

          • 2. Re: Eliminate problem particles?
            voxL Level 1

            Thanks.

            In the pics I posted, the faded green grad is a property map (I have it visible so we can see it), and it does speed the particles in the narrow area (the yellow line is the mask that controls the flow).  The problem is that as the path narrows, some of the particles are bouncing back rather than going thru, and then they just pool up and  bounce up and down - they are the ones on the left.

            I don't think the problem is related to the map, its the the narrow opening.  That's why I wonder we could write an expression which would look for the particles that aren't moving and delete them.

            • 3. Re: Eliminate problem particles?
              Mylenium Most Valuable Participant

              I think you are over-simplifying your approach. Actually what I meant was to forego real collisions entirely and make the particles travel solely based on maps. you see, per se there is no real reason for the particles to bunch up, but in your case it happens because you are only controlling them in a very small area with the map. A better way would be to let the gradient start much farther out, combine it e.g. with a Fractal Noise for turbulent movement, add secondary gradients to simulate bouncing as the particles come near the wall or make them slow down, so they never actually bounce, but rathe change direction before they do.

               

              Mylenium

              • 4. Re: Eliminate problem particles?
                voxL Level 1

                That sounds very interesting.  Do you freelance?  Would you be interested in setting that up?

                Thanks.

                • 5. Re: Eliminate problem particles?
                  Mylenium Most Valuable Participant

                  Sorry, I'm fully involved in a 3D animation project for the next 2 weeks still (after 4 months of unemployment, no less), and will not have much time. If I get around to it, I may be able to throw something together in what's left of my spare time give you a simple example project illustrating my points...

                   

                  Mylenium

                  • 6. Re: Eliminate problem particles?
                    Mylenium Most Valuable Participant

                    Okay, I couldn't resist. Find attached an example (CS3) that illustrates the technique. I just hoep it doesn't get stuck in the queue forever. If it does, just contact me off list (mylenium<|>at<|>mylenium<|dot|>de). If you're feeling generous, do a donation via my website...

                     

                    Mylenium