Objects - Display Volume

Owned by thomas (Unlicensed)
Last updated: 12 Jun, 2014
4 min read

With this set of options it is possible to visualize the object's own field in the form of a map with a colour gradient. The gradient colours illustrate in which areas, around the object, RealFlow will perform collision tests with grid fluids. The map's size also plays an important role, because the offset around the object's borders is connected to the “Cell size” parameter under “Volume” and indicates the area of interaction with grid fluid particles. The other “Volume”-related parameters also influence the map's size and look.

 

 

The mode of operation is exactly the same for each cutting plane and its related parameters. Volume maps can be neither rendered nor exported or transferred to other nodes. They are just a visual help to give you an idea how the current objects interacts with Hybrido fluids, for example when you see leaking grid fluid particles. We have prepared a detailed introduction about how to use these maps under "HyFLIP - Volumes and Distance Fields".

 

 

Isosurface

With this option you can visualize how the Hybrido fluid solver actually “sees” an interacting object. For this purpose, RealFlow takes all settings from an object's “Volume” panel into account. All changes will be displayed in real-time and you will be able to see where objects are leaking immediately. This feature will help you to adjust the interaction between the fluid and an object much faster, especially due to the fact that the “Isosurface” view can be combined with the “Slice plane [axis]” options, giving you the ability to visualize an object's signed distance field.


Cell size = 0.3 | Cell size = 0.05 | Cell size = 0.3, Surface offset = 0.2 | Cell size = 0.3, Volume mode = Solid outside
@ Color

Here, the isosurface's color is defined.

Slice plane XY | XZ | YZ

Switching this option to “Yes” draws a coloured map to the currently active object. The colours indicate the areas of interaction. You can choose which plane you want to show individually and it is also possible to activate all three cutting planes at once.

The map you see is the visual representation of a so-called Signed Distance Field (SDF). With SDFs it is easy to determine whether a particle is inside or outside an object and therefore often used for collision detection. The sign itself is an algebraic sign, e.g. +0.544 or -0.243. The surface points have a value of 0.0 – they are neither positive nor negative.

The map's total size depends on the object's “Surface offset” and “Domain offset” size. The higher value determines the map's dimensions. There are also commonly used names for each cutting plane:

  • XY = Coronal plane

  • XZ = Transverse plane

  • YZ = Sagittal plane

@ Type XY | XZ | YZ

“Display Volume” provides two different modes: “Ramp” and “Mask”. The first mode draws a colour gradient to the map and shows the increase/decrease of the distance field's value. The closer the values to 0, the stronger the red colour. In this mode, the red frame around the object's border has a size of Cell size * 2.

“Mask” is just a red-green map showing only the inner and outer parts: it tells you how the Hybrido solver “sees” the object, or how the object is rasterized. The smoothness of the red area directly depends on “Cell size” and smaller settings create a less jaggy mask. There is also a narrow gradient. The width of this band is equal to the object's “Cell size” value.

@ Offset XY | XZ | YZ

The maps slice through the object and show the SDF at the current position. Since an object's shape can vary, the SDF maps are different at different locations. With this parameter you can browse through the object and evaluate the distance field at each position. With the use of cutting planes, the size of an object is normalized and always ranges between 0 and 1. This way it is very easy to control the current position with the “@ Offset [XY|XZ|YZ]” parameters: 1.0 represents the top position, 0.5 is the node's middle, and 0.0 is the lowest point. The offset depends on the object's "Cell size" value and the map can only follow the grid in steps of "Cell size", e.g. 0.3, although it is possible to enter any value. An example:

Imagine an object with a "Cell size" of 0.1 with an activated "Slice plane" option. To shrink the SDF and fit it to the object's borders exactly you enter a negative value, e.g. -0.085. Now you start the simulation, but the particles still have a slight offset, and it seems as if your settings did not have the desired effect. The reason is that object is subdivided into cells of 0.1 metres and this is your step size for the "@ Offset [XY|XZ|YZ]" parameters. In other words, the only working values are integer multiples of the current "Cell size": 0.2, 0.1, -0.1, or -0.2 etc. So, if you want to adjust the SDF, take a look at the current "Cell size" and work with this value to adjust the SDF. Values, different from the step/cell size, are rounded by RealFlow.