Liquids

Winter 2016 FX Reel

Here’s my latest FX Reel:

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Flip Fluids: Mud and Water

This is a test to see how 2 liquids of different densities would interact. Each fluid also has separate viscosity settings.

To get this working I created a volume in sops, scattered points inside the volume, and then gave them custom point attributes to describe density, and viscosity. The water and mud were each assigned point groups, and then it was possible to separate them and assign the correct point attributes.

The mud has a varying viscosity from 100 to 1000,000 which creates the clumps within the mud. This is set in an attribute VOP in sops, and is driven by a random noise.

In dops the particles are fed into a Flip Object node, and the initial data input type is set to Particle Field to pick up the points created in sops. I also matched the particle separation value in the Flip Object node to the Points from Volume node used to created the points.

The liquids were meshed in Houdini and exported to Max using alembic.

The scene was rendered with Vray using a single dome light set to image based lighting with an HDR used for lighting and reflections.

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Houdini Flip Fluid Viscosity by age

Quick test to change the viscosity of a flip fluid by particle age.

A point attribute called birthframe is made in Sops so that each particle knows when it was born. Then in Dops a Popvop is used to read the birthframe attribute, and subtract it from the current frame of the sim which gives the particle’s age. This age is then passed to a fit range node which fits the value of 0 to 40, to 0 to 5000. This is the value written to the viscosity attribute on each frame.

Viscosity_popvop

This is what the flip section of dops looks like. The popvop is placed after the source volume for the flip fluid.

Viscosity_dops_network

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Houdini Flip Fluids in Max test

Krakatoa Particles playback in Max viewport

This is a first test of getting a Houdini Flip Fluids sim into Max for rendering in V-Ray.

I used the Krakatoa PRT Rop driver available from this site:

http://www.flipswitchingmonkey.com/2015/01/prt-export-from-houdini/

Which is pretty awesome. Drivers are available for Houdini 13 and 14. The version I tested was for 14.0335. The driver is easy to install, and is then available under a custom section of the Output drivers.

As well as baking out the particles to PRT files, the Rop driver can also write out the particle velocities, which are read by Frost back in Max. V-Ray is able to use the velocity data for in-camera montionblur.

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Realflow Water Test 01

Realflow Water Test 01 from Hugh Johnson on Vimeo.

Not added anything new for a while, but have an upcoming project requiring some water effects, so here’s my first Realflow water test.  Simming this in realflow didn’t take that long, so will increase the number of particles next time to get a better result. The render times on this are pretty heavy though at 12 mins a frame , so will have to come up with a better material for the water or face long render times in production.


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