REALFLOW to MAYA WORKFLOW
© Khoo Yi Hui 2009
Setting up RealFlow Preferences Go to File > Preferences
Choose this to select where you want RF to save or open your files from by default. (Pressing Default will reset the scenes folder to your default one under your program files.) Choose the axis setup. I use YZX for Maya. This is important as it affects the orientation of your object when you import them into RF / orientation of your mesh when you import them into Maya
Just make sure undo is enabled. Stack size is the number of undos you can go up to.
You can change the frame/extension order to this option so that the files names of your simulated particles and meshes is clearer (e.g. my file names now will be circle01_00001.bin instead of circle010001.bin) Padding size is the number of digits. Š Khoo Yi Hui 2009
Setting up RealFlow Preferences
It is better to change your frames per second value from your simulation options as it overwrites the value which you see under your preferences
Navigation ALT+LMB Æ Orbit in the perspective view ALT+MMB Æ Pan. ALT+RMB Æ Zoom
Help & Shortcuts Go to Help > Contents to access RealFlow help. It has quite a good record of what each emitter / daemon does. You may want to take a look at Help > Key Shortcuts . There isn’t a lot shortcuts to remember. Press F1 for quick help on what a parameter does (remember to have the parameter selected).
© Khoo Yi Hui 2009
Your Workspace Select Q); Move(W); Rotate(E); Scale(R)
Emitters
Daemons
Objects (you can import objects that you modelled from here)
Add Mesh
If you accidentally closed a window. Select this to spilt an existing window horizontally / vertically and select the first button to choose what window you want to open
You can switch between single view or quad view from here. (Shortcut : Alt W)
Start frame no.
The frame no. at which playback will stop
End frame no.
You can set position key / rotation key / scale key from here. (Shortcut: K, but that only sets position key)
Š Khoo Yi Hui 2009
Scale Scale in RF is a very important topic as it affects how detailed your fluid mesh can be. Each grid stands for 1 metre in real world scale by default. The bigger the scale, the more turbulence and details you will get in your simulated fluids (imagine the characteristics of splashing waves as compared to just water splashing out of a cup). By increasing the size of your emitters, you can increase the scale of your simulated fluids, but at much higher simulation time, so you will need to see how far your computer can take it.
The scale value that you see here is the scene scale value. It is useful when you have objects imported into RF. For example, you modelled an object in Maya, but when you import it into RF, it is much too big or too small. Changing the scene scale value will affect the size of all the objects that you have in your scene. You can then change the size of your emitters accordingly to a suitable value. The good thing about this is when you import the fluid mesh into Maya to render, you don’t have to worry that it is simulated using an object that has a different scale from what you have in your Maya scene. The imported fluid mesh will be scaled automatically to fit that of your Maya scene. If you have seen my animation CMYK, when I imported my well object into RF (to simulate fluid splashing out of it), it is too small for me to put a big enough emitter in the middle of it, but I cannot go back to Maya to increase the size of the well as I had already modelled the rest of the scene. So I increased the scene scale in RF instead. After finishing all the simulations, I can simply import the fluid mesh into Maya, and the size of the fluid mesh will fit the well automatically. Š Khoo Yi Hui 2009
Emitters Node Parameters for emitters like circle, square, linear, triangle Resolution is the amount of particles emitted. Higher resolution gives you richer and more detailed fluid behavior. Note that decreasing the scale of the emitter decreases the amount of particles emitted exponentially (and vice versa), so you will need to increase the resolution by a greater amount. Higher density Æ thicker fluids, slower particle movements Higher internal pressure Æ greater distance between each particle E.g. can increase this value if you want to fill a cup with particles faster Higher external pressure Æ particles will be more compact Higher viscosity Æ thicker fluids If you go up to higher resolution, might want to increase the max. particles that can be emitted. These closed tabs can be opened simply by clicking on them. You can change the display colour of your particles (useful when you have more than 1 emitter in your scene) under the Display tab Speed affects how fast/slow particles are emitted. Thus, higher speed will also result in greater amount of particles emitted. No particles are emitted at speed zero. V random and H random gives more variations / randomness to the way particles are emitted. Direction of emission
*Do note that what values to put these parameters to are relative to scale just like resolution. © Khoo Yi Hui 2009
Emitters For object emitter & fill object
There will be an option under the last tab for you to associate an object to the emitter. Just click on the Object parameter to select an object already in the scene. Object emitter emits particles from the faces / vertices of the object. Fill object fills up the inside of an object with particles.
For sphere emitter Change Fill sphere to Yes or the sphere emitter will emit particles in all directions from the sphere surface. (Increasing resolution will increase the amount of particles that fill up the sphere) You can also give a value to the Randomness to randomize the arrangement of the particles in the sphere. (but keep this value low at like ~1 if possible as particles will start flying all around when you simulate at high randomness values) Š Khoo Yi Hui 2009
Daemons Daemons are added in to affect the movement and thus shape that the particles can form
This means only particles are affected Both particles and objects will be affected
The k. stands for kill. These daemons help to reduce calculation time by removing unnecessary particles
The daemons which I usually use are underlined with orange. k.Volume is a must use to contain your particles. By default, particles that are outside of the k.Volume box will be killed off. You can also inverse it such that only particles that enter the boundary of the box will be killed.
Change to Yes
k.Isolated removes lone particles as they do not affect the fluid mesh much. Gravity is like what you know of it (you can change the direction of it if you want) Attractor pulls particles towards the point of attraction when its internal force value is positive, and repels at negative values. Wind simulates a typical wind force over particles. Noise field adds more randomness to the particles. Š Khoo Yi Hui 2009
Workflow Usually this is how I work: 1) Import the object(s) into the scene (if you are using them). Change the scene size if necessary. 2) Add in the emitter(s) and adjust the parameters like speed and V random and H random. I usually leave resolution at 1 first unless I changed the size of the emitter drastically. 3) Add in the daemons, especially k.Volume. Usually gravity will help too if not particles will just travel straight at a constant direction. 4) You might want to rename your emitters / objects / daemon if it makes things clearer for you. 5) Simulate (Shortcut: A) 6) Make the necessary changes and reset simulation (Shortcut: Ctrl A), then simulate again, or you can just press Simulate and overwrite existing frames. When testing the simulations you will want to make sure resolution is low so that simulation time is fast, but there must be enough particles emitted to let you know how the general shape of the fluid mesh will look like. If particles are flying around too much you can try increasing external pressure. Increase viscosity and/or density for thicker fluids. You might want to start setting keys on the speed value / position / rotation of the emitter for more variations. Right click on the parameter to Add Key Double click on the parameter to open the Curve Editor
Change this to bezier node if you want to adjust the tangent of the curves.
Š Khoo Yi Hui 2009
Workflow
You can also set keys on the daemons, like the value of gravity, or the internal force of the attractor or wind 7) If you are satisfied with the particles simulation, increase the resolution and simulate again. 8) At this point you might want to perform a preview of the simulation if the playback (press spacebar) is not fast enough. To preview, go to your Export Central (Shortcut: F12) Check Preview and set the image format
Then, just press spacebar to play the simulation and wait for RF to run through the timeline as it captures and saves the screenshots to your preview folder. When it finishes, open the image sequence using QuickTime (File>Open Image Sequence, and choose the appropriate frames per second) If it looks okay, we can go on to create the fluid mesh. *Remember to uncheck the preview!
Š Khoo Yi Hui 2009
Mesh
Add a new mesh into the scene If there’s only 1 emitter in the scene, it will automatically be attached to the mesh If there are more than 1 emitter, you need to right-click on the mesh(under the Nodes) and select Insert Fluids (You can choose what emitter(s) to be attached to the mesh)
There are only 4 main parameters that you need to change for the mesh node
1) Polygon size Usually you can start with values ~0.05 or 0.04 If polygon size is too large the details on the mesh will not show up, but smaller polygon size increases calculation time. 2) Set Filter method to Yes Higher Relaxation values eats away / thins out your fluid mesh. For a start you can leave the value at 0.1
Š Khoo Yi Hui 2009
Mesh Next click the tiny + sign beside the mesh node and select the emitter under it
3) Blend factor Higher blend factor increases continuity in the fluid mesh i.e. it will build a continuous mesh over particles which are further apart. 4) Radius If you set blend factor to zero, then only circular blobs will be created around the particles. The radius of these blobs is the value that you set for this parameter. Thus this is a highly sensitive value.
Note that radius and blend factor counters each other. Start by giving a value of ~0.01 – 0.03 to the radius. Test the mesh by right-clicking on the mesh node and selecting Build. Then adjust the blend factor value. If the edges of the mesh are still too round, try increasing the relaxation value. Test the mesh for a few different frames.
You can have a clearer view of the mesh by viewing the particles as Bounding Box and the mesh as Smooth Shaded. Select the emitter node then go to View> Element> Bounding Box etc
Š Khoo Yi Hui 2009
Mesh
When you are satisfied with your mesh, click the build mesh button and RF will help to build the mesh for all the frames *Anytime before this should you need to go back and adjust your particles simulation, remember to delete your mesh as pressing simulate will build both the particles and the mesh which takes much longer.
Global & Exclusive Links By default, everything in RF affects everything else. This can be seen from how everything that you added / imported appears under the Global Links. If you want something to affect a particular emitter only for example, 1) Delete the nodes involved from the Global Links 2) Drag the emitter node first from the Nodes over to the Exclusive Links window 3) Then drag the nodes which you want to exclusively affect the emitter only over to the Exclusive Links window and drop it on top of the emitter node
For this example, it means that particles from both emitters will affect each other; k_Isolated01 and k_Volume02 will also affect both emitters; Attractor01 and Gravity01 will only affect the Circle04 emitter, while Attractor03 will only affect the Circle05 emitter.
Š Khoo Yi Hui 2009
From RealFlow to Maya
First make sure that you have both Mental Ray and the RealFlow Plug-in loaded Go to Windows> Settings/Preferences> Plug-in Manager Load Mayatomr.mll and realflow.mll
A new RealFlow tab will appear in your shelf Import Mesh
SD Exporter You will have to export your object(s) as sd file if they have animation on them. Otherwise you can just export the object as obj file. (Remember RF can only read triangles so you will need to triangulate your geometry)
Choose the first file of your mesh sequence You can offset your mesh animation to start later. Otherwise it will start at frame zero
Š Khoo Yi Hui 2009
Rendering in Maya Go to your Hypershade (Windows> Rendering Editors> Hypershade) Here you can find all your rendering nodes
1) Right-click here and select Create mental ray Nodes
3) Middle-mouse click on the dielectric_material node created and drag and drop it onto your fluid mesh to apply it 2) Click on the dielectric_material and you will see a new node appearing under your materials
Š Khoo Yi Hui 2009
Rendering in Maya Select your fluid mesh and press Alt A to open up the Attribute Editor Click on the dielectric_material1 tab to access its options
Col generally affects the colour of your fluid as a whole. The higher the Index of Refraction, the greater the number of reflections and reflections in your fluid mesh. The default value of 1.5 gives quite a realistic render of water. Usually I keep the value very close to 1 to make it more like paint. Note that this is a very sensitive attribute. Outside Color shows up in the more complex / more detailed areas of your mesh. The more variations in the shape of your fluid mesh, the greater the amount of this colour that will appear. I haven’t play a lot with the Outside Index of Refraction but you can also try it out.
Increasing Phong Coefficient increases the brightness of the highlights in your mesh. It is not a sensitive value so you can increase it by multiples of 10 even. But the difference of adjusting this attribute is not always visible
Š Khoo Yi Hui 2009
Rendering in Maya Add a new camera into the scene (Create> Cameras> Camera) Look through the camera by going to Panels> Perspective> Camera1 (the camera name) You can also go to View> Camera Settings> Resolution Gate to see the framing of your scene. Navigate around the scene to your desired framing of the mesh
Select the camera from View> Select Camera Then press Ctrl A to access its attributes
Scroll down to open the Environment tab Change the Background Colour (I usually set it to white)
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Rendering in Maya
Click to access Render Settings
Choose mental ray
Where your rendered images will be saved to. To create or set your project folder, go to File> Projects
Set filename. These are the settings that I usually use for Image format, Frame/Animation ext, and Frame padding.
Set Start frame and End frame
Change this to your camera’s name
Change to your desired image size
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Rendering in Maya
Click to preview render
Next go to the Quality tab Change the Quality Preset to Preview Under Raytracing, make sure Raytracing is checked, and increase the Reflections, Refractions, and Max Trace Depth value to 6. I usually use these settings above when previewing my render. For your final render, you can change the Quality Preset to Production and the Filter to Mitchell. Or you can stay with your settings but increase the Max Sample Level to 2. Just note that at a small size like 640x480 sometimes you can even just stay with the preview settings (that I mentioned in the orange boxes above). Test it out whether is there much difference when you increase the quality that is worth the increased render time. Press F6 to access the Rendering menu set. You can batch render using Render> Batch Render *If you are wondering about lights, I’ve tried adding lights into the scene but they don’t seem to make any difference when I have a white background © Khoo Yi Hui 2009
Examples (Dielectric Material Settings)
© Khoo Yi Hui 2009
Examples (Dielectric Material Settings)
© Khoo Yi Hui 2009