MeVis Path Tracer

Introduction

The MeVis Path Tracer offers a state-of-the-art Monte Carlo path tracing framework that operates on CUDA GPUs. It supports high-quality, physically based rendering of:

• Volumes
• Triangle Meshes
• Lines
• Spheres
• Volume Slices
• Volume Instances
• Volume Isosurfaces
• Tag/Mask Volume + Per Tag Shading
• Clipping planes

It supports lighting and shadowing through:

• Area Lights (Rectangles and discs)
• Background Light (Image based lighting from a sphere or cubemap)

Various BRDF materials can be selected for shading:

• Matte BRDF
• Microfacet Blinn/Fresnel BRDF
• Principled BRDF

For low gradient values in volumes, we also support:

• Isotropic Phase Function
• HenyeyGreenstein Phase Function

The camera model allows for applying an depth-of-field effect. It supports both perspective and orthographic cameras, taken from the Open Inventor scene. To integrate with other OpenGL content, it can render the first hit depth to the depth buffer.

Credits

The MeVis Path Tracer is a completely refactored and substantially extended fork of the “ExposureRender” framework by Thomas Kroes, to whom we extend our gratitude for the insightful paper and for open-sourcing the renderer:

https://github.com/ThomasKroes/exposure-render “An interactive photo-realistic volume rendering framework”, T. Kroes, F. H. Post, C. P. Botha

The framework utilizes various third-party libraries, as listed in the MeVisLab “About” screen. It contains an MLPathTracer DLL that does not depend on Open Inventor and a SoPathTracer module that implements the Open Inventor bindings.

The framework uses various third party libraries, as listed in the MeVisLab “About” screen. It contains a MLPathTracer DLL, which does not depend on Open Inventor and SoPathTracer which implements the Open Inventor bindings.

Requirements

The first iteration is based on CUDA and only works on Nvidia GPUs.

Screenshots

The following screenshots demonstrate the various features of the MeVis Path Tracer, including volume instancing, meshes, clipping planes, image-based lighting, and depth of field:

Modules

The SoPathTracer is the main renderer of the framework and should always be positioned to the right in your scene. It collects the current Open Inventor camera and clipping planes and utilizes them during rendering.

There are various extensions that can be used:

• Volumes
  • SoPathTracerVolume: Loads and renders a volume; multiple volumes with arbitrary world coordinates are supported.
  • SoPathTracerMaskVolume: This can be used to mask voxels in SoPathTracerVolume volumes.
  • SoPathTracerTagVolume: This can be used to tag voxels in SoPathTracerVolume volumes.
  • SoPathTracerVolumeInstance: This can be used to render a SoPathTracerVolume with differnt transformation, subvolume, LUT, material, etc.
  • SoPathTracerSlice: Renders a slice at the specified plane, displaying the volume data of the given volume.
  • SoPathTracerIsoSurface: Renders an isosurface (with first-hit refinement) on the specified base volume.
• Geometry
  • SoPathTracerMesh: Scans the input scene for triangle meshes and ray-traces them.
  • SoPathTracerLines: Scans the input scene for line sets and ray-traces them as cylinders with rounded caps.
  • SoPathTracerSpheres: Renders a marker list as ray-traced spheres.
• Lights
  • SoPathTracerAreaLight: Provides a realistic area light with attenuation, area, and distance properties.
  • SoPathTracerBackgroundLight: Provides a background light using image-based lighting from a sphere or cube map.
• Material
  • SoPathTracerMaterial: Allows the specification of which material should be used for a given object.

Have a look at the example networks of the modules to learn how to use them.