The film Kon-Tiki is named after a primitively constructed balsa raft that floated an expedition team across the Pacific Ocean, nearly an 8000 kilometre journey stretching from South America to the Polynesian Islands. Over the course of their great journey the adventurers encountered a wide variety of ocean conditions, which is where Storm Studios lent their expertise using their collection of Houdini Digital Assets designed to makes waves for the ocean odyssey.
It was not just the crew of the Kon-Tiki that faced challenges on the high seas, Storm Studios had their own set of obstacles to overcome. The ocean they needed to recreate was colossal in scale and had generated enormous chunks of data. Also, their final renderings had to be photorealistic, as most shots had taken place during broad daylight, leaving no room to hide flaws.
Storm approached these challenges by building robust wave generation tools using Houdini’s digital asset technology. With digital assets, they could wrap up a technique into a single interface that could easily be used by a less experienced artist.
“The big advantage of using Houdini digital assets are that they are easy to reuse at a later stage,” says Magnus Pettersson, Lead FX Technical Director at Storm. “They also let us create and save good presets that can be transferred between shots. Having complicated node trees hidden while only displaying certain parameters makes it simpler to use for less technical artists or artists who are new to Houdini.”
The Houdini Ocean Toolkit (HOT) is a freely available toolset that is designed to create elaborate oceans based on the algorithms of Jerry Tessendorf. The asset that Storm crafted for Kon-Tiki was built made use of the VEX node from the Houdini Ocean Toolkit. The node was baked into the asset at the VOP level, allowing them to create custom controls for transforming and stretching ocean waves. The asset was used to displace points in the viewport to evaluate the results and then re-used in a shader to displace the geometry at render time.
To bring the large scale of the ocean under control, Storm combined four ocean assets to create their final ocean toolset. These assets were used in the displacement shader and in two geometry networks, one for rendering and the other for viewport display. The team then promoted parameters from the sub-network to the asset for top level control. This made it possible to control which of the four oceans should be displayed in the viewport, rendered as geometry or rendered as displacement. Breaking wave crests were also included in the asset by exporting values from the ocean asset into a custom VOP.
The vastness of the ocean caused very large amounts of data to pile up quickly in production. In one particular shot, a large ocean wave, carrying with it the Kon-Tiki raft as it crashed against an ocean reef, generated roughly one terabyte of data per iteration. The final iteration took five full days to simulate. With all this data rapidly accruing, it had to be very well managed. Houdini was chosen as the core tool in the team’s pipeline because of its ability to handle these large datasets.
Rendering With Mantra
Mantra was Storm’s renderer of choice because of its tight integration with Houdini. The team found it especially useful for underwater shots, such as where the Kon-Tiki raft catches on to the ocean reef or where water drops strike the ocean’s surface.
For the ocean reef shot they created their own rock shader in a very straightforward manner using Mantra’s Interactive Photorealism (IPR) tool.
“The ease of creating a specific shader from scratch in Mantra is superior to any other package we have used” comments Hans Jørgen Kjærnet, Senior TD at Storm. “We also did some cool trickery in Houdini to sample UV coordinates from the ocean floor to make a seamless texture transition blend to the reef.”
For the water drops, particles that hit the surface were read into the shader. The water ripples were generated at particular points using pre-simulated displacement maps allowing them to have very fine details in the displacements. For rendering closeup detail of splashes and whitewater, they filtered out whitewater particles that were then used to create a volume at render time by using a VEX volume procedural. This process had taken them one step closer to creating realistic whitewater while saving precious time when generating the volume.
For those situations where Storm needed to integrate elements such as geometry and camera/animation data from other apps into Houdini, they turned to the Alembic file format.
“It is much more effective than FBX or other similar formats and it blends very well into our pipeline” says Magnus. “We have built specific tools to automate our asset handling inside of Houdini and Alembic is at the core of this pipeline”.
When the Kon-Tiki raft crashed into the ocean reef on the atoll of Raroia, it reached its final destination, having conquered an ocean of adversity. Likewise, Storm Studios conquered what was an endless wave of data that was generated as they recreated the Pacific Ocean. With Houdini, they maintained the photorealistic look that the project called for while maintaining control over countless terabytes of data.
See the full VFX Breakdown HERE.