VisRTX renderer pro

Added in version 3.10.0.

VisRTX is a scientific visualization renderer based on the NVIDIA OptiX™ Ray Tracing Engine. It offers hardware-accelerated ray-tracing and can generate high-fidelity scene renderings including global illumination effects and shadows. Compared to CPU-based ray-tracing engines like Tachyon or OSPRay, this renderer can achieve near real-time performance on modern GPU hardware.

VisRTX requires NVIDIA hardware with CUDA support and a current NVIDIA graphics driver (CUDA 12.6+). The renderer is not available on the macOS platform and doesn’t work on Windows Subsystem for Linux (WSL), because this environment lacks the NVIDIA OptiX™ driver components required by VisRTX.

Caution

VisRTX is still under active development by the HPC Visualization Developer Technology team at NVIDIA in close cooperation with the OVITO developers, who integrate the technology. For more information, visit https://github.com/NVIDIA/VisRTX. Please report any issues you encounter to the OVITO developers.

Note

On first use of the VisRTX renderer, it will compile RTX shader programs for your GPU architecture. This process can take up to several minutes, but happens only once. The compiled shader programs get cached on disk and are reused in subsequent OVITO sessions.

Tip

The VisRTX renderer can also be used in the interactive viewports of OVITO to visualize the scene in real-time with high-quality ray-tracing effects. To enable the VisRTX renderer in the viewports, select it in the Viewports field on the Renderer tab of the rendering page or in the Viewport Renderer submenu of the viewport menu.

Parameters

The depth of field effect and the direction of the direct light source are specified on the Effects tab of the rendering page, because they apply to all rendering engines alike.

Quality settings

Samples per pixel: The number of ray-tracing samples computed per pixel of the output image (default value: 16). Larger values can help reduce aliasing artifacts.
Ambient occlusion samples: The number of samples used to compute ambient occlusion effects (default value: 8). Larger values can help to reduce visual artifacts.
Denoising filter: Applies a denoising filter to the rendered image to reduce noise inherent to ray-traced images (default value: on).

Ambient light

Brightness: Radiance of the ambient light source (default value: 0.7).
Occlusion cutoff: Maximum range of the ambient occlusion (AO) calculation (default value: 30.0). More distant objects beyond this cutoff range (given in simulation units) will not contribute to the computed local light occlusion effect. Decreasing this parameter will typically brighten up the inside of dark cavities that are otherwise fully occluded by the surrounding objects. Increasing it will make the AO effect stronger and lead to darker contrast.

Short AO cutoff range

Long AO cutoff range

Direct light

Brightness: Irradiance of the direct light source (default value: 0.4).

Materials

The surface appearance of the rendered objects is determined by the materials assigned to them, which are managed on the Materials tab of the rendering page and are independent of the rendering engine. The VisRTX renderer translates the shading model of a material as follows: the Diffuse shading model is rendered using the matte material from the ANARI specification, which reflects light uniformly into the hemisphere and is the fastest option. The Glossy and Physically based shading models are rendered using ANARI’s physicallyBased material, which behaves similar to glTF’s pbrMetallicRoughness material and consists of a mixture of a metallic and a dielectric/diffuse component.


Roughness: 20%	Roughness: 45%	Roughness: 60%
Metalness: 0%	Metalness: 40%	Metalness: 100%