Houdini

Vitality Pool – Houdini Flip Fluids Sim

I was asked to simulate a series of pools for a luxury development sales video, but I only supplied the final alembic caches for the water to be rendered in-house. So this is my render of the sim in V-Ray.

Houdini flip fluid sim, with a white water sim for the bubbles and foam. The water and the foam were exported as alembic caches into Max and rendered in V-Ray.

Vitality Pool – Houdini Flip Fluids Sim from Hugh Johnson on Vimeo.


Houdini Differential Curve Growth

Having a play with noise based curve growth with self avoidance.
Thanks to cgwiki for the original source file: tokeru.com/cgwiki/index.php?title=HoudiniDops
and some great info and sample files on odforce: forums.odforce.net/topic/25534-differential-curve-growth/

I used pop streams to control the point velocity at the base of the shape otherwise it goes crazy. The mesh was exported as an alembic (7GB!) and rendered in V-Ray.

Houdini Differential Curve Growth from Hugh Johnson on Vimeo.

2nd version:

I wanted to calm the movement down compared to the previous test. So I keyed the pop drag from 1 to 10 as the shape growth progresses to slow the growth down.

I also changed the settings on the POP interact so that it wouldn’t repel the other points with as much force, The Position Force is set to 1.5 and the Velocity Force is at 1.

For this test I wanted to create a shape with a lot of intersections and came up with this.

After the curve is generated in pops, I use another resample to smooth the line again, and then use a poly wire node to generate the geometry on the curve. It’s then exported as an alembic and brought into Max to be rendered with Vray. Before rendering I subdivide the alembic again to get rid of the occasional poly spike made by the Poly Wire node.

Houdini Differential Curve Growth v02 from Hugh Johnson on Vimeo.


Honda Robots – Made Mean

I was the senior FX TD on this project and was responsible for the flamethrower fx, robot cable sims, paint spray, logo branding and any heat haze effects.

Honda_Lighting_Master30s_v60_H264_FullRes from Hugh Johnson on Vimeo.

In addition to the main 30 second commercial, we also delivered 3 10 second commercials. I was involved in this one where I simmed all of the tyre smoke:

Honda Socials 'Nutjob' from Dave Walker on Vimeo.


BBC Christmas Ident FX Look Dev

FX Look Development for a specific shot in the BBC Christmas ident involving falling clumpy snow. Using Houdini’s Grain Solver I delivered a proof of concept shot of the wet snow falling on a test object. The simulation was saved as an Alembic file and imported into 3ds Max where I set up the V-Ray shader for rendering realistic snow.

 

Here’s the whole ident with the falling snow shot at 16 seconds in:

BBC – Christmas – Sprout Boy from Factory Studios on Vimeo.

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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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