This page provides general information about the Mesh sub-section of the Rendering rollout of Chaos Phoenix.
Overview
The options for this rollout are accessible when the Render Mode is set to Mesh, Ocean Mesh, or Cap Mesh.
UI Path: ||Select PhoenixFDSim|| > Attribute Editor > Rendering rollout > Mesh rollout
Parameters
Mesh Type | rendMeshType – Specifies the type of mesh to render.
Static Mesh (V-Ray) - this mode will generate a V-Ray Static mesh type at render time. Static geometry is generated at the beginning of the rendering and remains in memory until the frame is rendered. This can speed up the rendering but will increase the memory usage.
Dynamic Mesh (V-Ray) - this mode will generate a V-Ray Dynamic mesh type at render time. Dynamic geometry is generated 'on the fly' which can potentially save memory. Not recommended when Render Mode is set to Ocean Mesh.
Maya Mesh (not suitable for Ocean) - this mode will generate a standard Maya mesh that can be rendered with renderers other than V-Ray. When you enable Show Mesh from the Preview rollout, this mesh is also available in the viewport for processing as any other Maya geometry. This way it can be exported to Alembic for example, from Maya's Cache → Alembic Cache menu. If the Render Mode is Ocean Mesh or Cap Mesh, the generated mesh will have low detail because the Phoenix ocean mesh is deliberately low-res in the viewport preview for performance reasons. In Maya Mesh mode, you can use the Velocity Color Set field to control the name of the color set with vertex velocities that will be needed for rendering the mesh with motion blur. The vertex velocity is in Units/Second.
Switching to Maya Mesh mode will create a new TexUVW UV set, if you have enabled the TexUVW channel in the Output rollout before running your simulation. In order to use the new UV set you need to select the Maya Mesh and link the TexUVW UV set from the Maya Relationship editor. Switching away from the Maya Mesh mode will reset the UV sets, so if later you decide to switch back to Maya Mesh mode you will need to relink the UV set again.
Prevent MoBlur Self Intersection | rendMbSelfIsect – In all Mesh modes, some motion blurred vertices might penetrate the opposite side of the geometry. When enabled, this option prevents such situations. The self-intersection analysis is expensive, so enable this parameter only when an intersection is obvious.
Phoenix meshes are motion blurred in a different way than regular transforming and deforming geometries. When rendering regular meshes with motion blur, the entire mesh is moved along its transformation path back and forward in time, and so each individual vertex of the mesh follows this path. However, for each rendered frame, a new Phoenix mesh must be built from the voxel grid, and so it usually has a different number of vertices than the previous and the next frame. Because of this, individual vertices can not be traced back or forward in time between frames. Instead, motion blur of fluid meshes uses the velocity of vertices which is recorded by the simulation, and moves each vertex back and forward in time along the vertex velocity. This is why the generated liquid mesh does not support frame sub-sampling for motion blur. This may cause a mismatch between the liquid and transforming/deforming objects in your scene that interact with it. The fluid mesh is generated from data at the exact rendered frame and fluid data for the preceding or following frames is not used, unlike regular deforming meshes. As a consequence, the liquid and the objects in your scene would synchronize best if those objects do not use additional geometry samples for motion blur.
Velocity Color Set | rendMayaMeshVelSet – Available only in Maya Mesh mode. You can use this field to control the name of the color set with vertex velocities that will be needed for rendering the mesh with motion blur. For example, VRayProxy in 3ds Max and Maya looks for a color set named 'v' or 'velocity'. Phoenix automatically transfers this name to the standard Maya motion vector color set under Mesh Shape → Mesh Controls → Motion Vector Color Set field, so you'd get motion blur in Maya Mesh mode. In order to export the mesh as Alembic with included Phoenix velocity, make sure to enable Write Color Sets in the Advanced Options of the Alembic Export window. This workflow is covered in the How to export a Phoenix FD cache to Alembic video.
Note that the Phoenix velocity color set keeps the velocity in scene units per second. This way Alembic caches exported from it can be loaded via a V-Ray Proxy in 3ds Max or Maya, and also via the built-in 3ds Max Alembic importer. However, rendering the Maya Mesh directly or importing it via Maya's built-in Alembic importer would read the velocity in units per frame, so you might have to adjust Phoenix's Motion Blur Multiplier in the Rendering rollout prior to rendering or export, in order to reduce the length of the motion blur.
When exporting Alembic caches with vertex velocity using Maya's built-in exporter, make sure that a Phoenix frame exists for the starting frame of the sequence and that it contains velocity. Otherwise the entire exported Alembic cache will not have vertex velocity.