Creating a waterfall using object emitter
In this Real Flow tutorial we will create waterfall using an object emitter. Now before starting the tutorial let me explain what an object emitter does.
Object emitter emits particles from the selected faces or vertices of an object. You can also use a texture to emit particles from an object in a particular shape. But to do that the texture applied to the object must be in black and white color, being black non emission area and only objects from an .sd file will have the ability to emit particles from textured object.
Note: The emission is made per polygons, if those polygons are nor big enough for the current resolution, it won’t emit.
When this happens, use the global scale to increase the size of the objects or increase the fluid's resolution.
To create a waterfall first we will make the surface which will be used to emit particles in real flow. So for that we will create a poly plane in Maya. Triangulate the plane and export it as an .Obj file.
Note: That you have enough faces and vertices to emit particles from the plane.
Now import this .OBJ file in real flow and add an object emitter.
Now that we have added the object emitter. Let’s simulate and see what happens. Well as you can see in the image below. There are no particles emitting from the object.
So in order to get particles emitted from this object select object emitter under Nodes.
Then click on blank right in front of Object under Nodes Params – object emitter.
A select element window will pop up showing the plane object. Select plane and hit Ok.
You will see the plane in front the object under Nodes Params – object emitter. Let’s move the plane up in Y axes, to give some height for the water to fall down.
Now click on the simulate button ones again to check what happens.
Even now we don’t see any particles coming out of the object. That’s because the resolution for particles is very low. So lets set it to something like 200.0 and let’s also set the viscosity to 1.0 because water is not very thick or viscous.
So let’s go to Node Params and change the resolution and viscosity under particles.
Now if you will simulate you can see a bunch of particles coming out of the plane.
So now when we can see the particles lets make them fall down by adding some gravity. Click on the daemon button right next to emitter button and click on gravity.
But again if you will simulate one more time you will see that even after adding gravity still the particles are moving upwards instead of falling down.
So let’s change the strength of gravity from its default value of 9.8 to something like 50.0. You can do that by selecting gravity in your scene window or nodes window. Then go to the Node Params window then change the value in front of Strength under gravity.
Let’s simulate one more time and you will see that the water is falling down.
But if you will notice closely that there is some distance in between particles and the plane. To correct that lets change the parent velocity to 50.0.
And also change some more parameters to give our waterfall a more natural effect. Change the value of Jittering to 0.2 and Randomness to 2.0 under object emitter in nodes params window.
We also want our waterfall to fall down in one direction, so let’s add the wind daemon it’s below the gravity daemon.
Move the wind daemon up in y near the plane and rotate in Z around -25 degrees.
And let’s simulate to see the effect.
If you look carefully around the edges of the plane some particles are still falling down from other three sides of the plane to avoided that we will select the vertices to define the area from where the particles will emit and also use the K Volume daemon.
So by defining particle emitting area and adding K Volume daemon we will not only improve our project but it will also help use in saving some simulation time.
To define the area for particles to emit we will select the vertices of the plane.
To select vertices of the plane select the object emitter then go to object emitter’s properties and click on select vertex.
Then drag the mouse with the Shift key pressed to select vertices. All the selected vertices will turn yellow like in the next image. Leaving the three edges of the plane unselected.
Now add the K volume daemon this demon can be used as crop tool. We will use k volume daemon to keep particle flow in a particular area.
Note: K Volume daemon looks like a cube and can be moved, rotated and scaled.
Place and scale the k volume daemon so that all the three edges of the plane are slightly outside the covering area of this daemon.
And here is the end result. You can also add a plane at he bottom to give a base to your water fall.
Note: All given values are based on scene scale.