GUIDED SCENE
Compositing particles
Binary Loader 2: Modeling the stream


Vid1: Like a Rolling.... errr.. Water Stone?

This tutorial will show you some emission tricks and how to set up particles with object interacion.

What we want to do, is create a ring of fluid that we will use to build a sphere in the next tutorial..

1.- The first thing to do is to decide wich emitter to use. So, let's see how we can achive the effect.

    Let's take a look at the emitters list... Oh, well there is no growing sphere emitter, so we will need to find out how to do it:
    • We could use a sphere emitter, but is going to look like a growing sphere, we are misssing the formation. It would be the same as scaling a spehre... that's too simple.
    • We could animate an emitter moving around an imaginary sphere and freeze the particles using the speed daemon (Max=Min=0)... that would be cool, but not for this tutorial!
    • What about just a cricle emitter throwing particles inside a spherical object so the particles make a loop defining a perfect ring? Then we could use that ring several times from different angles to complete the sphere.
      Something like this:
      

    This seems to be an easy task, but that's not going to be a perfect sphere. As the particles are emitted from the circle emitters into the sphere we are going to need something to remove those particles from the mesh generation.... Don't worry, we'll get to that later.
2.-Setting up the particle loop.
    As I don't want you to copy exactly what I do, I'm just going to tell you how to do it step by step , and what it should look like.
    Lets get started:
  • Create a new project and add a circle emitter.

  • Bring in a spherical object. Since we are not going to need the sphere for rendering and it's not going to be modified, we don't really need to use a SD file. I'm going to be using a 1 meter obj sphere.

  • The emitter is way to big or the ball is too small. I'm going to increase the size of the ball. But how?... scaling (from node), or using the global scale??...
    I'm going to use the global scale (at top of the interface). I could use the node scale, but I would have to type the scaling factor for each axis.

    The global scale will only affect objects so I don't have to worry about the emitter, but that's not the most important thing. The most important thing about using the global scale is that RF is going to change the properties of the object to fit this new shape, things like mass or collision distance will be set to fit the new shape.

    Okay then, I'll use the global scale to go for a sphere that's five times as big.
    You may also be wondering... Why didn't he scale the emitter?. The answer is easy, becasue I like using the standard RF resolution of 1. That will help to keep my numbers clear, and just in case we are going to use fluid or gas, by using a resolution of 1, we are going to get the standard fluid behaivor.. I'll get back to this later.
    Place the emitter so it's set like in the image above.
  • 3.-Setting up interactions.
    • Go to the scene tree (F11) to make the emitter interact with the object. Just press the 'add all' button at the scene tree.

      Press action and the particles will collide with the object. bHowever, we need them to collide with the inside of the sphere.


    • We need to change the collision side of the sphere
      so the particles don't collide with the outside of the object Select the sphere object and click over the particle interaction tab. By deafult RF will set an object to collide using both sides of a face. To change that, switch the collision side to Inward.


    4.-Saving out those particles.
    • Open the export central (F10). The export central shows everything than can be saved with RF.
    • As there is only one emitter in the scene and we want to save it, just press save 'All emitters'. You will see that the emitter named 'circle01' is checked. Also, a blue square will appear at the end of the time line, pointing out that an emitter has been savde.
      As particles are going to be saved, you will be able to play the simulation back.


    5.-Setting up the Emitter.
    • Press action. Now the particles are going inside the sphere and colliding with the inside faces.
      REMEMBER
    • Disable the viewport visibility (Alt+D) to speed up the simulation.
    • Run the simulation and you should get something like this:

          


      If not, move the emitter to keep the emission inside the ball from the beginning, but don't worry if some particles go outside of the sphere weh the fluid completes a loop. Remember that you can use the xform particles to move the particles with the emitter


    • The emission is made by layers and if those layers are too noticeable, we are going to get a bubbly mesh.



      To avoid those layers we can add some variation to speed emission. A good rule is to set the V random to half the value of the Speed



    6.-Setting up the simulation.
      At this point there are two issues: The simulation is not running fast, and the fx is taking too long.
    • Speeding up the simulation: This simulation is really simple, there are no big forces in between particles or daemons or object dynamics or other emitters. It's just a fluid colliding with a ball, and we don't really need the computation to be precise.
      This is a good example of when the substep can be decreased..
      Since we are going to be playing with the subsetp, this is the perfect momeent to save if you have not do so yet. Lowering the substep will casue some instabiliy.
      Go to the simulation options. There you will find the Max and Min substeps which, by default, are set to 1 and 333 respectively.
      Take down the 'Max substep' and hit action. Try using 100 instead of 333. The simulation looks similar but now the calculation is faster.
      Try different settings but don't go extremly low or RF will fry your computer! This simulation is so simple that can be handled even with a max step of 2 (although it's not recommended you do that). I'll we using a max substep of 20.
    • Speeding up the fx, This is looking right, but the particles are traviling slowly. I want this to be 3 times faster. We could just increase the emitter speed, although keep in mind that changing the speed will also change the fluid behavior.
      As we decided that we only want the simulation 3 times faster, the fastest solution is to change the FPS (options panel) from 30 to 10. This means that the simulation is going to be the same, but RF will not oputput 30 frames per second, just 10.

    • Run the simulation again. It should look like this one:

          


    6.-Removing the leak.
    • As the particles complete the loop, they avoid the new particles to get into the sphere.


    • This means that the particles inside the sphere are affecting the particles on the outside.
      By activating the thin face test for the sphere(particle interacion) the particles at one side of the object will not affect the other side.
      But this is not going to completly solve the leaking beacuse there is too much pressure coming from the fluid on the inside.


    • We are going to have to delete those particles using a destruction daemon; in this case a ~Volume Destruction daemon. As there is just one emitter in the scene, any daemon added will automatically be added to the emitter, so we don't need the export central. Set the ~Volume daemon to Inverse and place it where the leak is. (See the image below)




    7.-The Final Touch. (optional)
    • The emission from the circle emitter is too thick. I'm just going to use another destruction daemon, to remove half of the emission.
    • Clone the actual volume daemon, set it to interact with the emitter (scene tree), and place it as in the following picture.




      8.-...And the stream is done!
      • Run the simulation again. We are only going to be using the first 120 frames, so you don't need to run it until the end.

      Get the scene files
      Go to the next Tutorial >> Compositing Particles.(Binloader)