Simulating in Houdini: Destruction & Transformation

Simulating in Houdini: Destruction & Transformation

David Gao talked about amazing simulations made in Houdini including destruction, apple rot, and skin transformation.


Hello, 80 Level! My name is David Gao, and I am a 3D generalist with an FX specialization from San Francisco, California. I got my undergraduate degree in design at UCLA, and recently graduated from Lost Boys School of VFX in Montreal. I found my way to 3D through music, getting inspiration from artists creating visuals for music. As a 3D generalist, I’ve worked on some interesting projects, such as creating tour visuals for Joji, Big Gigantic, and Martin Garrix (with Strangeloop Studios) and assisting on a robot installation called “Telestron” for GMUNK and VT Pro Design. After a few years of freelancing, my hunger to learn more led me to Lost Boys School of VFX, where I spent the coldest winter of my life in Montreal studying FX.

Disco Destruction

This project was my own twist on the conventional house destruction exercise. We were provided a procedural house by our instructor that we were to destroy. I used Houdini’s material based destruction, which had just shipped with version 17. This allowed me to quickly shatter the parts in wood, concrete and glass patterns, as well as constrain them. After destroying them in DOPs, I used the debris tool, which creates points at areas of separation, to spawn particle debris. Houdini’s procedural workflow allowed me to wedge test dozens of destruction sims, and art-direct the final shot. Since I already destroyed the house with spheres, the disco balls were already halfway done. To create the individual mirror faces of the disco ball, I faceted unique points along each face and then extruded them. The ground reflections of the disco ball were created spotlights that emitted caustic photons which rendered quickly with Redshift. I couldn’t help but make some dorky sound design to go with this shot as well.

Rotting Apple

This was one of our first exercises at Lost Boys, taught by industry veteran Sean Lewkiw, and one of my most successful effects. I achieved this rotting effect with a combination of geometry deformation, lattice deformation, and material change. While this all sounds simple enough, the key to a convincing effect was the fine-tuning of the shader and stacking dozens of noises. The apple had three main stages, “good”, “bruised” and “rotten”, and each one had its own characteristics. Little details I added such as dots in the reflection, a gradient in the rotting color, folding the skin of the apple over itself in the rotten areas, and changes in roughness helped to create a realistic… and disgusting look. I first attempted to shade the apple using Redshift, however, I found that Mantra had more complex noises and was more flexible in layering.

Mystique Skin Transformation

This is a personal work that I have been wanting to create for some time. I wanted to create a tool that would create this transformation effect on any geometry fed into it. It is based on a solver that transfers attributes that deform the scales inside a for-loop. The scales are scaled (no pun intended), rotated, as well as bent (though it is too fast to notice) during the transformation. The scales have one material on one side, and a different material on the other side. While they transform on the skin of the geometry, the material also changes underneath. I also added some nice little customizable features such as the ability to tweak the shape of the scale, and ability to add swirl patterns in the growth of the scales. Adding some billowy smoke, particles, and dramatic lighting helped to finalize the shot.

Fire Explosion

My fire explosion shot was one of my most ambitious scenes because it was quite difficult to keep track of all the different moving parts. First, I had to rebuild the entire cathedral to be destruction friendly, since the original model had numerous intersections. I used a number of methods, including cloning/symmetries, booleans, and VDBs. I then worked on a bricking tool that cuts each part of the building into tiling bricks. Then it was just a matter of constraining them all together and running a few dozen destruction sims. I rendered this scene in Redshift, taking advantage of its speed, especially with pyro. In total, this scene took nearly two months to create.

Working in Houdini

The most useful aspect of Houdini is without a doubt the procedural workflow. It forces me to clean up my pipeline, and create things with purpose and efficiency. Working procedurally also encourages me to not just replicate the subject’s appearance, but also learn why it looks or acts the way it does.

On specific pieces of Houdini, I have found the recent addition of material based destruction and vellum to be really useful. The consistent flow of great updates with each release keeps me on my feet and excited for what’s next. Most of all, it satisfies my hunger for learning. I love the feeling of realizing that there’s so much I don’t know.

For beginners, I highly suggest finding a course series with a good instructor and following along from the very start to get the fundamentals down, instead of jumping into anything fancy right away.

I am currently working on some personal work, including content for my YouTube and Instagram, where you can find other works and works in progress.

Thanks for reading, and thank you 80 Level for having me!

David Gao, 3D Generalist & FX Artist

Interview conducted by Kirill Tokarev

Join discussion

Comments 3

  • Darion

    Wow! This article has been very helpful to me to understand the realistic time limitations of doing many simulation based projects. Thanks also for the insight as to what the projects at Lost Boys VFX school are like.



    ·3 years ago·
  • jasmine

    this is so cool! as someone who doesn't really understand the process of making simulations, i liked the explanations and it makes me appreciate the amount of work and creativity that's involved in making them.



    ·3 years ago·
  • Everyone

    can stop posting this kind of low-quality 'showcase' articles?
    If I wanna find showcase/reel, I can find them easily on Viemo, cgsociety.

    Everyone know houdini can be used to do destruction, simulation, etc.
    there is no need to show another destruction unless posting a helpful 'tutorial'.
    However, this is not.



    ·3 years ago·

You might also like

We need your consent

We use cookies on this website to make your browsing experience better. By using the site you agree to our use of cookies.Learn more