Introduction.
V-Ray GPU offers fast interactive feedback for look development and final rendering. Faster iterations free up time to explore ideas, boost productivity, and produce better results. This article presents the workflow of interactive rendering in V-Ray GPU, along with some valuable tips to help you maximize your hardware's performance.
Settings to control interactive rendering can be located in the IPR tab within V-Ray for Maya:
- IPR Rays Per Pixel (value range from 1 to 8 ) - the number of rays that are traced per pixel for one image pass. The higher the value, the smoother the image will be, plus it increases GPU usage on high-end cards like the RTX 3090.
- IPR Ray bundle size (value range from 128 to 512) - controls the number of rays processed together in a bundle during interactive rendering.
- Undersampling (value range = 0 to 4) - controls the initial sampling rate of the image. If set higher than zero, V-Ray renders the image at a lower resolution to speed up the initial preview.
Recommended settings for various hardware configurations.
Below are presented ready-to-use presets for a variety of hardware configurations, based on internal testing, to ensure optimal performance and GPU usage. The 'Undersampling' value is a matter of personal preference, so feel free to experiment with it.
Preset for high-end GPUs(RTX 3090 and RTX 4090):
- Rays Per Pixel 4
- Ray Bundle Size 256
- Undersampling 2
Preset for mid-range GPUs(RTX 3060, RTX 2080ti):
- Rays Per Pixel 2
- Ray Bundle Size 256
- Undersampling 2
Preset for low-end GPUs (RTX 1080, RTX 2060 Super):
- Rays Per Pixel 1
- Ray Bundle Size 128
- Undersampling 2
Preset for multiple high-end GPUs:
- Rays Per Pixel to 8
- Ray Bundle Size to 512
Use of the NVIDIA AI denoiser in interactive rendering.
The NVidia AI Denoiser uses AI to guess what the image should look like without the noise. It works well with high-frequency noise in early passes of interactive rendering, and it calculates super fast on GPU. It suits interactive rendering very well.
In V-Ray 6 you will be able to pick a dedicated device for the AI Denoiser if you have multiple GPUs in your machine. This improves the interactive performance as well as GPU memory usage as denoising happens on a separate device. This could be done in Maya’s UI or the standalone Device Select tool. In the below example, Denoising is set to the RTX 3090 (that is also used for monitors), and marked by *** next to its name. Which means it is connected to 3 monitors in the system. The RTX 4090s are dedicated to GPU rendering in this case:
Standalone Denoising Tool
Device Selector in Maya
Note: NVIDIA AI Denoiser is not consistent when denoising render elements if used for final rendering. This means that there will be differences between the original RGB image and the one reconstructed from render elements that are denoised with the NVIDIA AI Denoiser. It also doesn’t support cross-frame denoising and will likely produce flickering when used in animation. For final rendering, it is recommended to swap to V-Ray or Intel’s Denoisers.
Workflow for Interactive rendering in V-Ray GPU.
Start by adding the Denoiser Render Element, and set it to the NVIDIA AI Denoiser. You can set an Engine for IPR rendering in V-Ray for Maya and a different one for final rendering.
Maya UI example.
Set the Denoiser update frequency using the Post Effect Rate in the settings tab. For high-end GPUs, this could be set to 100 which means the denoiser will update as frequently as possible.
Note: for final rendering, if you are using Progressive mode you will need to set Post Effects Rate to 0 for optimal performance. You don’t want the Denoiser to update every second for the final rendering.
In the IPR tab set the IPR Rays Per Pixel and IPR Ray Bundle Size from the presets above. In this case, the high-end GPU preset for the RTX 4090 was used. Also, setting the Max Noise to 0 for interactive rendering is a personal preference. Here is a preview of these settings in action.
Note: by default, V-Ray for Maya uses BF/BF GI for interactive rendering, for interior scenes it is recommended to enable the option for GPU Lich Cache in the IPR tab.
Use of GPU Light Cache in interactive rendering.
GPU Light Cache is recommended for interior scenes, where illumination relies on indirect lighting. It gives more accurate lighting and avoids noise, although it reduces the interactivity of the scene drastically, as GPU LC needs to calculate for every change or camera movement.
Note: it is recommended to use values between 750 to 1500 for GPU LC Subdivs for interactive rendering. This will improve GPU LC performance and overall responsiveness for interactive rendering. Then you can increase this value to 2000 to 3000 for final rendering.