This page provides general information about the Displacement sub-section of the Rendering rollout of Phoenix FD.
Displacement is a technique intended to add detail to the simulation during the rendering. The idea of the Phoenix displacement is similar to the usual geometry displacement: a texture is sampled, and the corresponding point of the fluid volume or surface is shifted in a direction at a distance determined by the texture. You can plug any V-Ray, Maya or Phoenix texture maps.
You can use the Phoenix FD Simulator's Mesh Preview option to check how the attached displacement map is affecting the surface when Mode is set to Mesh, Ocean Mesh or Cap Mesh.
UI Path: ||Select PhoenixFDSim|| > Attribute Editor > Rendering rollout > Displacement rollout |
Displacement Amount | rendDispl, rendDisplEnbl – Specifies a displacement strength multiplier.
Texture | rendDisplFine – Specifies the displacement map. Depending on the Type option selected, a monochrome map or a color map could be required. If a colored map is specified when a monochrome map is needed, the strength of the displacement is determined by the total intensity of the color. If a monochrome map is specified when a vector map is needed, the entire displacement will point in a single direction. See the Advection Displacement with a Monochrome Map example below.
The Type parameter is ignored when Mode is set to Mesh, Ocean Mesh or Cap Mesh. In these modes Phoenix automatically recognizes whether the texture map is monochrome or colored and used respectively Surface-driven or Vector displacement. The difference between Surface driven and Vector displacement is that vector displacement can produce more complicated surfaces. For example, a wave texture in Vector mode produces waves that have a convex back side and a concave front side, in contrast with the symmetrical forms produced by Surface driven displacement. |
Type | rendDispltSurf – Specifies the displacement technique.
Gradient driven – Requires a monochrome texture map. The displacement amount is the texture's brightness at each point. Each point of the fluid is shifted along the gradient of the Surface channel. This means that each point in space could have a different displacement direction. This method is suitable for smoke and fire.
Surface driven – Requires a monochrome texture map. The displacement amount is the texture's brightness at each point. Each point of the fluid is shifted along the normal of the point's projection on the isosurface of the fluid's Surface channel. The texture is also sampled at the projection point. Unlike the Gradient driven displacement, this ensures that all points above of below the fluid surface will be displaced in the same direction, and so displacing fire/smoke simulations produces better results that are more similar to displaced solid geometry surfaces. However, the Surface driven method is slower than Gradient driven.
Vector – Requires a colored vector texture map (with negative and positive values). The point is shifted by the texture color, interpreted as a 3D vector.
Advection – Requires a colored 0.0-based vector texture map (with negative and positive values). A very similar method to Vector, but does not produce grainy structures for fire and smoke. It requires Can be combined with the Phoenix Grid Texture, with its Channel set to Velocity, to produce render-time gridless advection. For more information, see the Advection Displacement example below.
Vertical Fade Level | rendDisplFade, rendDisplVertFade – Specifies a vertical zone above the Ocean Level, where the displacement will be strongest. Above this zone there will be no displacement at all, and inside this zone the displacement will gradually be reduced moving up from the ocean surface. This is needed so that the ocean displacement would be applied only near the ocean surface and not to any simulated fluid splashing high above the ocean surface. This parameter is a percentage of the grid height, just as the Ocean Level option.
Fade Above Velocity | rendDisplVelFade, rendDisplVelFadeEnbl – If the fluid velocity (in voxels/sec) in a voxel is higher than this value, there will be no displacement at all. When the velocity is lower than this value, the higher the velocity, the weaker the displacement will be. This allows you to suppress displacement for the fast moving parts of the fluid where the displacement would visibly disturb the motion in an unnatural manner, and thus you can have only the still ocean surface displaced with waves. This option requires the Grid Velocity channel to be exported to the simulation cache files from the Output rollout.
The Fade Volume feature can be used when the liquid is in contact with a geometry surface such as a shore or a ship and the displacement breaks the contact by moving the liquid mesh away from, or into the geometry. |
Use Fade Volume | usefadeobj – When enabled, allows you to specify a geometry object as a fade volume. There will be no displacement inside this object and outside it the displacement will be gradually reduced at a distance specified by the Volume Fadeout Distance parameter.
Set Selected Object as Fade Volume - When a polygon mesh and a PhoenixFDSimulator are selected, the selected object will be used as the displacement Fade Volume of the simulator.
Fade Volume | usefadeobj, fadeobj – Specifies a geometry that is going to be used to zero out the displacement inside its volume. There will be no displacement inside this object and outside it the displacement will be gradually reduced at a distance specified by the Volume Fadeout Distance parameter.
Volume Fadeout Distance | displgeomfade – Specifies the distance in world units around the object where the displacement will fade out.
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This example illustrates how displacement is affected when a monochrome map is passed when a vector map is needed.
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Regular smoke and fire, 5M cells
