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title: "About V-Ray RT"
canonical: "https://documentation.chaos.com/space/DOCSGUIDE/113289540/About%20V-Ray%20RT"
format: markdown
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> Due to unforeseen volume of inquiries....Open the documentation for more information, [click here](https://learn.enscape3d.com/knowledge-base/).
## **Overview**
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## **Workflow**** **
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V-Ray RT can be selected for **ActiveShade Mode** or **Production Rendering Mode**, or both. To start using V-Ray RT, choose one of the modes as the **Target** in the **Render Setup **window, and assign **V-Ray RT** as the **Renderer**.
## **V-Ray RT Options**
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To access the settings of V-Ray RT after assigning it as the renderer, select the appropriate mode for the **Target** in the **Render Setup** window and click the **V-Ray RT** tab.
**The V-Ray RT settings described here are for ActiveShade Mode. If V-Ray RT is selected for Production Rendering Mode, some parameters are not available.**
### **Shading**
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**These options can speed up the rendering process. Using a simple shader on the entire scene and lowering bounce numbers greatly improves the response time of V-Ray RT. This added interactivity is useful while working on the overall lighting, motion blur, or any other aspect of the image that doesn't rely on 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, so long as they don't exceed the value specified here.
**GI depth** – The number of bounces for indirect illumination. Other GI settings (i.e.. whether GI is enabled or disabled) are taken from the production V-Ray renderer. The GI depth is disabled if the secondary GI engine is the light cache - in that case, V-Ray will configure the GI bounces automatically.
**Auto update bitmaps** – When enabled, V-Ray RT will try to automatically update the rendered image whenever one of the bitmaps used in the scene is changed on the disk.
**Use 32 bit frame buffer** – When enabled, V-Ray RT will attempt to create a floating-point 32-bit frame buffer which contains HDR information.
**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 option is grayed out. If this option is enabled during rendering, it is grayed out again, making it impossible to restore interactivity once the buffer is locked. To restore interactivity, restart the rendering.
**Override mtl** – When enabled, this option causes objects to be rendered with a selected material rather than their assigned materials, but only if an override material is selected. This option does not affect actual material assignments; it only affects the materials as they appear in the RT rendering.
**None** – Click to select the override material.
**Exclude** – Brings up the 3ds Max Include/Exclude window for selecting objects to include or exclude from the override material assignment.
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### **Performance**
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The parameters in this section affect the performance of V-Ray RT. Note that the optimal values for a given machine and network configurations might be different from the defaults. The best way to find the optimal values for any one system is through experimentation.
**Ray bundle size** – Controls the number of rays that are sent to the V-Ray RT render servers for processing. 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. Conversely, larger sizes increase the speed of the renderer but decrease interactivity. 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 might be significantly diminished. Increasing this value also reduces the amount of data transferred from the render servers back to the client machine.
**Progressive RPP** – 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** – When enabled, 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.
**Show statistics** – When enabled, some useful values are shown in the upper right corner of the V-Ray Frame Buffer window:
V-Ray RT version
Number of calculated camera paths (i.e. image samples) per second, in thousands (Kpaths/s)
Time elapsed since the current image started rendering. This value is reset whenever a change is made to the scene that requires recalculation of the image.
### **Rendering**
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**Max time (min)** – Specifies the maximum time (in minutes) for refining the image.
**Max paths/pixel** – Specifies the maximum samples per pixel for refining the image. This option is particularly useful when **Production Renderer Mode** is set to **V-Ray RT** as it ensures consistent quality of the different frames. V-Ray performs adaptive sampling on the image, trying to put more samples into areas that have more noise.
**Max. noise** – A threshold that determines when to stop refining a pixel. Higher values allow more noise in the image, while lower values try to reduce the noise. A value of 0.0 traces the entire image unconditionally.
**Note**: The **Show mask** option is removed in 3.10.x versions. Please use the [VRaySampleRate Render Element](https://docs-chaos.atlassian.net/wiki/pages/createpage.action?spaceKey=docsguide&title=Sample%20Rate%20%7C%20VRaySampleRate&linkCreation=true&fromPageId=113289540) as an alternative.
**In-process RT engine** – When enabled, the actual rendering of the image happens inside the 3ds Max process. This speeds up the initial scene translation phase and the improves the interactivity of ActiveShade rendering. When disabled, a separate V-Ray standalone render server is launched in DR mode to perform the actual rendering. This option might need to be disabled if V-Ray RT cannot find suitable GPUs for rendering with the CUDA or OpenCL engines. An example is when there are an AMD and an nVidia GPU installed in the machine, and the AMD GPU is used for handling the user interface and 3ds Max viewports whereas the nVidia GPU is only used for rendering.
**Distributed rendering** – Enables or disables distributed rendering for V-Ray RT. Use the **Render Servers** button to specify machines that will be used for distributed rendering.
**Render Servers** – Opens the **V-Ray interactive renderer DR settings** window.
### **V-Ray Interactive Renderer DR Settings Window**
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**Add server** – Click to manually add a server by entering its IP address or network name.
**Edit server** – Click to change data about a render server.
**Remove server **– Deletes the currently selected server(s) from the list.
**Resolve **– Resolves the IP addresses of all servers.
**Use local host** – Determines whether V-Ray RT should run on the local machine when DR is used. When enabled, V-Ray RT will run on the local machine as well as on all machines included in the distributed rendering. When disabled, V-Ray RT will not run on the local machine and instead it will only use the render servers. Use this option when the local machine is needed for other computational tasks.
### **Engine**
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These parameters specify options for the back-end engine used by V-Ray RT. Making the right selection for the rendering hardware can speed up V-Ray RT.
Use of a GPU engine requires a video card that supports Open*CL 1.1* or higher, or *CUDA 2.0* or higher. The CUDA engine or V-Ray RT GPU works on NVIDIA cards with the Fermi, Kepler, Maxwell and Pascal architectures. For users of NVIDA cards, the use of CUDA engine is recommended when rendering with V-Ray RT GPU.
**Type** – Specifies the back-end for the RT engine. The possible values are:
**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. The recommended choice for nVidia GPUs.
**Coherent tracing** – When enabled, V-Ray RT will attempt to spawn secondary rays (GI, reflection etc) in similar directions in order to improve rendering speed on certain GPUs.
**Resize textures for GPU** – Enable this option to resize high-resolution textures to a smaller resolution in order to optimize memory usage. This parameter is only effective when **Type** is set to **Open CL (single kernel)** or **CUDA (single kernel)**.
**GPU texture size** – When **Resize textures for GPU** is enabled, this value specifies the resolution to which the textures will be resized.
### **Geometry**
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This section controls various options for the RT engine. One of the goals of the RT engine is to serve as a fast preview of the scene, so sometimes it is not needed to display the scene as fully as it appears in the Production renderer.
**VRayProxy objects** – When enabled, V-Ray proxy objects are rendered by the RT engine. Note that on the GPU, proxies do not have their memory-saving properties as they have in the CPU engine and the production renderer; currently, they are replicated everywhere they are needed. This will be optimized in a future release of the V-Ray GPU engine.
**X-Ref scenes and containers** – When enabled, the RT engine will also display X-Ref scenes and containers.
**Particle systems** – When enabled, the RT engine will display particle systems.
**Displacement** – When enabled, the RT engine will display render-time displacement through the VRayDisplacementMod modifier.
**Motion blur** – When enabled, the RT engine will respect the motion blur settings of the production renderer or the physical camera, if one is used. Motion blur is supported both by the CPU and GPU engines. When V-Ray RT is used as a production renderer, this option is always assumed to be enabled and is greyed out.
### **Stereo / Additional Displays**
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V-Ray RT can render a stereo view of the scene in multiple formats. Note that if this tool is used, V-Ray RT ignores any *VRayStereoscopic* helpers in the scene; the stereo output is controlled only from the V-Ray RT options. This section includes tools to duplicate the RT engine output to another window that can be maximized on a secondary display. Whenever an additional window is displayed with this option, double-click the window to toggle between a maximized window and a window at its original size. The additional windows are for display only; they don't support navigation like the ActiveShade window.
**Type** – Determines the type of additional (stereo) display:
**Disabled** – Stereo rendering and additional display is disabled, and a single image is rendered in the ActiveShade window.
**Side by side** – The left and right views are displayed in separate windows that can be maximized on different displays.
**Interlaced** – A separate window displays an interlaced blend of the left and right eye images. This is useful for displays that support interlaced stereo.
**Checkered** – A separate window displays a checker blend of the left and right eye images. This is useful for displays that support checkered stereo.
**Anaglyph (Red, Cyan)** – A separate window displays a red/cyan anaglyph preview of the stereo images. Matching anaglyph glasses are required to view the stereo effect.
**Anaglyph (Green, Magenta)** – A separate window displays a green/magenta anaglyph preview of the stereo images. Matching anaglyph glasses are required to view the stereo effect.
**OpenGL stereo** – A separate window alternates between the left and right eye images. Matching active shutter glasses and supporting video card are required to view the stereo effect.
**Duplicate (mono)** – Duplicates the contents of the ActiveShade window so that it can be maximized on another display. This is not a stereo mode.
**Swap left/right** – Swaps the left and right eye images.
**Eye distance** – The distance between the two virtual stereo cameras, in world units. The cameras are always focused at the camera target for the current view.
**Note**: By default the focus type is *shear*, where each eye's view is sheared along the Z axis so that the two frustums converge at the fusion distance. The internal parameter for changing the focus type for this display to another type (such as *rotate* or *parallel*) is accessible only through MaxScript.
### **Messages**
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The RT engine can output diagnostic messages. The messages normally appear as an overlay over the rendered image in the ActiveShade view.
**Warn for non-physical settings** – When enabled, the RT engine will display warnings for non-physical settings (i.e. GI multipliers different from *1.0,* invisible lights, etc).
**Warn for unsupported features** – When enabled, the RT engine will display warnings about features of the production renderer that cannot be represented properly in the current RT engine (CPU or GPU).
**Message delay (s)** – The number of seconds that information messages and warnings stay on the screen. Set to *0* to disable information messages.
### **.vrscene export**
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The* .vrscene* file format is the scene description format used by the standalone version of V-Ray. V-Ray RT allows you to export your 3ds Max scene to this format for subsequent rendering with V-Ray Standalone outside of 3ds Max. *.vrscene* files can also be exported directly from MaxScript using the vrayRTExportScene global MaxScript function.
**Export .vrscene** – If enabled and the full file path, name and extension are set, the 3ds Max scene is exported to the specified *.vrscene* file when the V-Ray interactive renderer is started.
**Don't render (just export)** – Allows the scene to be only exported without being rendered. The ActiveShade session will be closed as soon as the *.vrscene* file is created. Note that currently the scene is exported only for the current frame, without animation.
## **V-Ray RT GPU Render Devices Selection**
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This rollout is shown whenever the V-Ray RT engine type is set to OpenCL or CUDA to specify which GPU devices to use for in-process rendering. It is equivalent to the external utility *Select OpenCL devices for V-Ray RT GPU* that is included with V-Ray (*ocldeviceselect.exe*), but allows the devices to be changed without restarting 3ds Max.
## **3ds Max controls**
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Normally, as a different viewport is made active, V-Ray RT will update the ActiveShade window to show the new point of view, if it is a Perspective or Camera viewport. You can prevent this behavior and lock V-Ray RT to a specific view by turning on the **Lock View** button in the **Render Setup** window.
**View to Render** – This dropdown is used to select the view to be rendered when V-Ray interactive renderer is started. Only Perspective and Camera views are supported for the moment. Note that if you lock to a particular view, and later on change the number of viewports (i.e. by maximizing another viewport), V-Ray RT may not be able to show the locked viewport.
**Lock View** – The button next to the **View to Render** dropdown. If enabled, selecting different viewports in 3ds Max will not have any effect in V-Ray interactive renderer. You can lock/unlock the rendered view even while V-Ray RT is rendering.
## **ActiveShade in Viewports**
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The ActiveShade button in the Render Setup window starts the V-Ray RT renderer in a separate window. The size of the window is determined by the **Width** and **Height** values under the **Common** tab. However, the ActiveShade renderer can also be started in a 3ds Max viewport by choosing **ActiveShade** as the display for the particular viewport. In that case, the size of the rendered image is the same as the size of the viewport.
To return an ActiveShade viewport to its normal state, right-click anywhere in it, and choose **Close** from the quad menu.
## **Notes**
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- The viewport must be a Perspective or camera viewport when you turn it into an ActiveShade window. Orthogonal views, including User views, are currently not supported.
- The ActiveShade state of a viewport is saved with the 3ds Max scene. If you save the scene in a state where one of viewports is an ActiveShade window, when you load the scene later on, 3ds Max will automatically start V-Ray RT for the same viewport. In that case, V-Ray RT will display a short warning and will not actually start rendering.
- If the **Show Safe Frame** option is enabled for the viewport, the rendering is restricted inside the safe frame.
- Resizing the viewport after the V-Ray RT renderer has started is not recommended as it can lead to unexpected results.