V-Ray RT is an interactive rendering engine for Maya. To use it you must have V-Ray assigned as a rendering engine and use the IPR function of Maya. This rollout allows you to control the settings of V-Ray RT.
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, as 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.
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.
CPU Ray bundle size / GPU Ray Bundle size - These control the number of rays that are sent to the V-Ray RT render servers for processing when using V-Ray RT running on CPUs or GPUs respectively. 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.
CPU Rays per pixel / GPU 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.
Show statistics - When this option is enabled, some useful values are shown in the upper right corner of the V-Ray Frame Buffer window:
Auto-start local slave - when on V-Ray will automatically start a render slave on the local machine for rendering with RT. When of V-Ray will only used render slaves specified in the distributed rendering settings.
Max. render time (min) - 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.
Max. paths per pixel - 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
Max noise - 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.
Show mask - when enabled the user can see a mask that shows which parts of the image are currently being refined.
Lock render buffer - 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.
Type - this option allows you to switch between V-Ray RT running on CPUs (CPU) and GPUs (Open CL single kernel)
Enable - enables the rendering of a stereoscopic image
Eye distance - specifies the eye distance for the stereoscopic vision
VRayProxy objects - controls whether or not VRayProxy objects will be rendered by V-Ray RT
Particle Systems - controls whether or not particle systems will be rendered by V-Ray RT
Displacement - controls whether or not displaced geometry will be rendered by V-Ray RT
Subdivision - controls whether or not render time subdivided geometry will be rendered by V-Ray RT
Hair - controls whether or not Maya hair objects will be rendered by V-Ray RT
Fur - controls whether or not VRayFur objects will be rendered by V-Ray RT
Restart when the Render Layer changes - when enabled V-Ray RT will automatically restart when a different Render Layer is enabled