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This page provides general information about the Displacement sub-section of the Rendering rollout of Chaos Phoenix FD.

Overview

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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 on the mesh of the fluid volume or surface is shifted in a direction at a distance determined by the texture. You can plug both any V-Ray and regular , Maya or Phoenix texture maps, as well as the PhoenixFD Ocean Texture. 
You can use the Phoenix FD SimulatorPhoenix Simulator's Mesh Preview option to check how the attached displacement map is affecting the surface when rendering a Liquid simulationsurface when Render Mode is set to Mesh, Ocean Mesh or Cap Mesh.

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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. For more information on texture mapping in Phoenix, please check the Texture mapping, moving textures with fire/smoke/liquid, and TexUVW page. See the Advection Displacement with a Monochrome Map example below.

Type | rendDispltSurf – Specifies the displacement technique.

Gradient drivenGradient driven – Requires a monochrome (black and white) texture map. The point is shifted toward the field's gradient by the texture brightness. 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. The Gradient of a channel is the direction in which the value increases. In the case of a plume of smoke, the center is the densest area, and a Gradient-driven Noise displacement map will appear as bumps all over the smoke surface. 
Surface driven – Requires a monochrome (black and white) texture map. The point is shifted by the texture brightness toward
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 . The of the fluid's Surface channel. The texture is also sampled at the projection point. The Surface driven method is slower than Gradient driven but   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  The point is shifted by the texture color, interpreted as a 3D vector. This  This displacement mode is intended to be used with the Ocean Texture | PhoenixFDOceanTexture texture but the Phoenix Ocean Texture but can be used with any other vector displacement texture.

• • If Mode is set to Mesh, Ocean Mesh or Cap Mesh, then it requires a texture in the format used for V-Ray Tangent Vector displacement, where X and Y of the texture are 0.5-based, and the Z direction is 0.0-based. This means that if you use a texture where the Red and Blue colors are gray and the Green color is black, it will produce no displacement; brighter color than these will move the fluid points along the positive axes, and darker and negative colors will displace the fluid point along the negative axes. A texture in such a format is the Phoenix Ocean Texture in Vector Mode.
  • If Mode is other than the mesh modes, Vector displacement requires a texture which is 0.0-based, so black color means no displacement, brighter colors shift the fluid points towards the positive axes and negative colors - along the negative axes. Such a texture is the Phoenix Grid Texture with its Channel set to Velocity.

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. Can be combined with the the Phoenix Grid Texture | PhoenixFDTexture, with the Grid Texture's 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.

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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.

Example: Advection Displacement

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Column width 10% Column width 40% Regular smoke and fire, 5M cells Column width 40% Advection displacement with the simulation's own Velocity, using a PhoenixFDTexture and multiplied by a Noise map. Column width 10%

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MonochromeMap MonochromeMap

Example: Advection Displacement with a Monochrome Map

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