This page provides information on the three RT rollouts in the V-Ray RT and Performance Render Settings.


Page Contents



V-Ray RT is an interactive rendering engine for Modo that gives fast feedback on the rendered result as you work on your scene. V-Ray RT has some hardware requirements that can be found on the GPU Rendering page.

UI Paths:

 ||V-Ray RT and Performance render settings|| > RT - Shading rollout

 ||V-Ray RT and Performance render settings|| > RT - Performance rollout

||V-Ray RT and Performance render settings|| > RT - Stop Conditions rollout


 ||V-Ray RT and Performance render settings|| > RT GPU - Textures rollout


RT - Shading

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.


RT - Performance

Note: The optimal values for a given machine and network configurations may be different from the default values. The best way to determine optimal values for specific hardware and scene requirements is experimentation.



CPU / GPU Ray bundle size – Controls 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, 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 / GPU Rays per pixel – Number of rays that are traced for each pixel during one image pass. The greater the value, the smoother the image's illumination from GI from the very beginning of the rendering, but interactivity might be significantly diminished. When using distributed rendering, increasing this value also reduces the amount of data transferred from the render servers back to the client machine.

Progressive rays per pixel – When enabled, V-Ray RT starts rendering the image with a lower Rays per pixel value and then progressively increases it. This speeds up the initial preview of the image.

Undersampling – V-Ray RT starts rendering the image at a lower resolution in order to speed up the initial preview. Later the image is rendered at its final resolution. Increase this number to start at lower resolutions.


RT - Stop Conditions

Max. render time (min) – Specifies a maximum amount of time (in minutes) for V-Ray RT to render or refine a render before it stops.

Max. paths per pixel – Limits 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 RT will stop rendering.

Max. noise – Specifies a noise threshold for V-Ray RT. Once the threshold between pixels has been met, V-Ray RT will stop rendering.


RT GPU - Textures




Use On-demand Mipmapping – Instead of loading all the texture files at their default resolution (original or resized), V-Ray will load the textures as needed and will automatically create mip-map tiles for them (regardless of their texture type). As a result, the GPU memory consumption could be decreased; textures that are not visible will not be loaded, and textures that are further away from the camera will be loaded with lower resolution. During the texture detection process, V-Ray GPU will render slower. Once it detects that all textures are loaded, it switches automatically to the traditional (faster) mode. A message about modes changing will show up in the V-Ray log.

GPU Resize Textures – Optimizes memory usage when rendering on the GPU by controlling the texture size.

Full size textures – Textures are loaded at their original size.
Resize all textures – Adjusts the size of high-resolution textures to a smaller resolution in order to optimize render performance. The GPU engine will load as much texture tiles on the GPU as it can, then swap the ones that are needed between GPU RAM and CPU RAM.

GPU Texture Size –When rendering with V-Ray RT GPU CUDA, and GPU Resize textures is set to Resize textures, this parameter specifies the resolution to which the textures will be resized.

GPU Texture Format – Controls the file format of the material textures used in GPU rendering. Selections are 8-bit, 16-bit and 32-bit per channel. This does not affect textures used for lights and displacement.