This video contains three treatments of a gravitational tides project using Houdini FLIP fluids.
The project uses two radial gravity POP Wrangle nodes using identical VEX (which I discussed in my last blog post, Houdini FLIP Fluid and Radial Gravity) apart from the definition of the origin attribute. The orbiting satellite geometry, unsurprisingly named satellite, drives the origin for one of the radial gravity nodes:
float x = ch("../../satellite/tx");
float y = ch("../../satellite/ty");
float z = ch("../../satellite/tz");The source for the fluid surrounding the main planet is simply a small sphere copied and scattered over a larger sphere that's approximately the same size as the Mountain deformed sphere that forms the main planet's geometry.
Both the main planet and the satellite are rigid bodies so that the fluid flows around them. So, with the two gravity nodes, the fluid, and the rigid bodies, my DOP Network looks like:
The satellite's orbit decays in the second and third clips. This is done with some simple trigonometry with the radius of the orbit based on the current frame number:
Easy! My main planet only has a radius of 2.7 meters, so I've dialed down the scale time on the DOP Network to 0.1. Giving it a start frame of -50 ensures the fluid has nicely settled around the little mountains on the main planet.
Thank you for this; Earth's tides and waves totally make sense now!
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