Phoenix Simulator → Volumetric Heat Haze and Isosurface rendering is not supported yet with V-Ray GPU and V-Ray GPU IPR.
Phoenix Particle Shader → Cellular Render Mode is currently not supported with V-Ray GPU and V-Ray GPU IPR.
If you are using Phoenix 5.10 or later, you will need the latest V-Ray 6 Stable build to get correct results when rendering the Phoenix Particle Shader with V-Ray GPU.

List of the Supported V-Ray Features

Chaos Phoenix 5.24 Official Release	V-Ray 6 CPU	V-Ray 6 GPU	V-Ray 6 CPU IPR	V-Ray 6 GPU IPR	V-Ray 7 CPU	V-Ray 7 GPU	V-Ray 7 CPU IPR	V-Ray 7 GPU IPR
Phoenix Simulator, Volumetric Render Mode	✓	✓	✓*	✓	✓	✓	✓*	✓
Phoenix Simulator, Volumetric Geometry/Volumetric Heat Haze/Isosurface Render Mode	✓	✓ Volumetric Heat Haze and Isosurface are not supported.	✓	✓ Volumetric Heat Haze and Isosurface are not supported.	✓	✓ Volumetric Heat Haze and Isosurface are not supported yet.	✓	✓ Volumetric Heat Haze and Isosurface are not supported yet.
Phoenix Simulator, Mesh/Ocean Mesh/Cap Mesh Render Mode	✓	✓	✓	✓	✓	✓	✓	✓
Particle Shader	✓	✓ Cellular Mode is not supported.	✓	✓ Cellular Mode is not supported.	✓	✓ Cellular Mode is not supported yet.	✓	✓ Cellular Mode is not supported yet.
Particle Shader, Render as Geometry	✓	✓ Cellular Mode is not supported.	✓	✓ Cellular Mode is not supported.	✓	✓ Cellular Mode is not supported yet.	✓	✓ Cellular Mode is not supported yet.

* - Phoenix Simulator → Volumetric Render Mode is supported since Phoenix 5.01.00, Nightly Build: 31567, from 09 Aug 2022.

Phoenix Particle Shader → Points and Cellular Render Modes are not supported with V-Ray 5 GPU and V-Ray 5 GPU IPR.
If you are using Phoenix 5.10 or later, you will need the latest V-Ray 5 Stable build to get correct results when rendering the Phoenix Particle Shader with V-Ray GPU.

Chaos Phoenix 5.24 Official Release	V-Ray 5, update 2.3 CPU	V-Ray 5, update 2.3 GPU	V-Ray 5, update 2.3 CPU IPR	V-Ray 5, update 2.3 GPU IPR
Phoenix Simulator, Volumetric Render Mode	✓	✓	✓*	✓
Phoenix Simulator, Volumetric Geometry/Volumetric Heat Haze/Isosurface Render Mode	✓	✓ Volumetric Heat Haze and Isosurface are not supported.	✓	✓ Volumetric Heat Haze and Isosurface are not supported.
Phoenix Simulator, Mesh/Ocean Mesh/Cap Mesh Render Mode	✓	✓	✓	✓
Particle Shader	✓	✓ Points and Cellular Modes are not supported.	✓	✓ Points and Cellular Modes are not supported.
Particle Shader, Render as Geometry	✓	✓ Points and Cellular Modes are not supported.	✓	✓ Points and Cellular Modes are not supported.

Phoenix Simulator → Volumetric Geometry/Volumetric Heat Haze/Isosurface rendering is not supported with V-Ray Next CPU IPR.
Phoenix Simulator → Volumetric Heat Haze and Isosurface rendering is not supported yet with V-Ray GPU and V-Ray GPU IPR.
Phoenix Particle Shader rendering is not supported with V-Ray Next GPU and V-Ray Next GPU IPR.

Chaos Phoenix 5.22 Official Release	V-Ray Next CPU	V-Ray Next GPU	V-Ray Next CPU IPR	V-Ray Next GPU IPR
Phoenix Simulator, Volumetric Render Mode	✓	✓	✓*	✓
Phoenix Simulator, Volumetric Geometry/Volumetric Heat Haze/Isosurface Render Mode	✓	✓ Volumetric Heat Haze and Isosurface are not supported.	✗	✓ Volumetric Heat Haze and Isosurface are not supported.
Phoenix Simulator, Mesh/Ocean Mesh/Cap Mesh Render Mode	✓	✓	✓	✓
Particle Shader	✓	✗	✓	✗
Particle Shader, Render as Geometry	✓	✗	✓	✗

V-Ray Features Support