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Volumetric Fog in KartaVR

This video shows the results from a VR workflow R&D experiment where CG rendered volumetric fog was added to a live action stereoscopic 360° panoramic forest scene with the help of my KartaVR for Fusion plug-in.

About This Volumetric VR Workflow

This is a grid layout that shows the 6 Sony A7Sii based circular fisheye views.

The original live action footage was filmed at 4K resolution on Sony A7Sii based panoramic stereo rig that captured the scene using a series of six views photographed with a super wide angle Peleng 8mm circular fisheye lens.

My single camera based stereo 360° rig works by combining a Jasper Engineering stereo slide bar with a Nodal Ninja panoramic head.

Stereo 360° 3D Panoramic Head

This stereo footage was loaded into Fusion Studio and stitched by KartaVR.

A nice thing about the Sony A7Sii based panoramic camera rig is that it provides plenty of image resolution at a low noise level so the fisheye “stereo pair” views could be successfully run through a computational disparity mapping approach. Disparity mapping works by calculating the X and Y shift for every pixel in the two stereo images.

The Fusion based disparity technique was used to good effect in this project to create the multi-channel z-depth data that is needed later on to control the placement of volumetric 3D fog in the panoramic scene. This depth image data allows the real world filmed trees to intermix with the computer rendered fog layer so the correct density is used as the fog stretches out into the distance in the scene.

Disparity mapping was used on the circular fisheye stereo imagery to create a depth map for each of the trees in the scene.

The slightly harder part of adding the CG rendered fog effect was that it needed to be applied realistically to the KartaVR stitched stereoscopic 360° footage and feel like it was an integrated part of the scene.

This is a stereo disparity generated panoramic 360° depth map that was created and stitched in KartaVR + Fusion Studio from the Sony A7Sii imagery.

The varying density in the fog was achieved using a panoramic version of the Fusion “FastNoise” node. Several math expressions were used on the procedural noise generator to create the animated texture that drives the motions of the volumetric fog in the 360° stereo scene.

This expression based animation approach when combined with Z-depth data provided the natural looking variations of the pockets of higher and lower density fog whisps that blow through the scene in a consistent and reliable way.

Equirectangular Screenshot

This image is a framegrab from the right eye view in the equirectangular movie clip that is viewable at the top of this blog post.

You can see the mostly spruce forest in the foreground of the panorama, a bit of CG rendered fog starting to roll into the scene in the mid-ground, and the rugged rocky shoreline of Powers Lake in the background.

KartaVR made it possible to add animated volumetric fog to this West Dover filmed forest scene.