This is a legacy documentation space! Please refer to the V-Ray Next for Rhino help for most up-to-date information.

VRay RTEngine Overview


V-Ray RT is an interactive rendering engine for Rhino. To start using V-Ray RT you can simply left mouse click the RT button from the main V-Ray toolbar. You can always switch back to the V-Ray production renderer by clicking the RT button with the right mouse button.

To start V-Ray RT manually you must first start a local DRSpawner. Next, you must enable from the RTEngine rollout in the V-Ray renderer parameters. Finally you must enable Distributed Rendering from the System rollout of the V-Ray renderer parameters.

General Options


Enable  - turn on or off the V-Ray RT engine.

Refraction Caustics  - this allows indirect lighting to pass through transparent objects (glass etc). Note that this is not the same as Caustics, which represent direct light going through transparent objects. You need refractive GI caustics to get skylight through windows, for example.

Reflective Caustics  - this allows indirect light to be reflected from specular objects (mirrors etc).

Note that this is not the same as Caustics, which represent direct light going through specular surfaces. This is off by default, because reflective GI caustics usually contribute little to the final illumination, while often they produce undesired subtle noise.

Trace depth  - Represents the maximum number of bounces that will be computed for reflections and refractions. The individual material reflection/refraction depth settings are still considered, so long as they don't exceed the value specified here.

GI depth - the number of bounces for indirect illumination. Other GI settings (e.g. whether GI is enabled or disabled) are taken from the production V-Ray renderer.

RT Mode - this option allows you to switch between V-Ray RT running on CPUs (CPU) and GPUs (Open CL single kernel)

  • CPU - the CPU engine is used. This engine does not require a graphics card and supports many of the regular V-Ray renderer features, including procedural textures and complex materials.
  • OpenCL (single kernel) - a GPU engine based on OpenCL is used. This engine uses graphics cards that support OpenCL and can be very fast depending on the hardware, but has somewhat limited abilities with regards to shaders. The OpenCL and CUDA engines have the same set of capabiltities, but for NVIDIA GPUs it is recommended to use the CUDA engine.
  • CUDA (single kernel) - a GPU engine based on the NVIDIA CUDA platform. This engine uses NVIDIA graphics cards that support CUDA and is the recommended engine for NVIDIA GPUs. Like the OpenCL engine, it can be very fast, depending on hardware, but has limited abilities with regards to shaders. The OpenCL and CUDA engines have the same set of capabilities.

It is recommended to use the CUDA engine on NVIDIA cards.

OpenCL Texture Size - the number of bounces for indirect illumination. Other GI settings (e.g. whether GI is enabled or disabled) are taken from the production V-Ray renderer.

AA Threshold - specifies a noise threshold for V-Ray RT. Once the threshold has been met for a certain part of the image V-Ray will stop sampling it and will divert rendering power to parts of the image that require more sampling.

Max Render Time - since V-Ray RT uses progressive path tracing it would never stop rendering unless specified otherwise. This option allows the user to specify a maximum render time in minutes.

Show AA mask - when enabled the user can see a mask that shows which parts of the image are currently being refined.

Maximum Sample level - this parameter allows the user to limit the maximum quality achieved by V-Ray RT by specifying a maximum number of rays traced for each pixel. Once the specified number has been reached V-Ray will stop rendering

Lock Viewport - Locks the render buffer so no further changes to the scene are reflected in the rendering window (however V-Ray RT continues to refine the image). It should be noted that before V-Ray interactive renderer is started, this check box is disabled. During rendering if you check it on, it is disabled again making it impossible to restore interactivity once the buffer is locked. The only way to do that is by restarting the rendering completely.

Stop when render done - this stops the render based on the Max render time or the Maximum Sample level.

Performance


The parameters in this section affect the performance of V-Ray RT. Note that the optimal values for a given machine and network configurations may be different from the defaults. The user is encouraged to experiment with these values to find the optimal ones.

Ray bundle size  - This controls the number of rays that are sent to the V-Ray RT render servers for processing. When using distributed rendering, the smaller sizes cause more frequent client/server communication with smaller network packets thus decreasing the speed of the renderer but increasing the interactivity and vice versa. Note that this number is not the exact amount of rays, but is proportional to it. It is not recommended to increase this value beyond 512.

Rays per pixel  - The number of rays that are traced for each pixel during one image pass. The greater the value, the smoother the picture from the very beginning of the rendering with GI, but interactivity may be significantly diminished. Increasing this value also reduces amount of data transferred from the render servers back to client machine.

Notes


  • When using V-Ray RT and Distributed Rendering you must disable localhost or 127.0.0.1 from your distributed rendering servers. For additional information on distributed rendering, please
    refer to the dedicated Distributed Rendering section.