Rocket sims with Maya fluids

With the new machine put together, Maya 2015 installed, and some down time, I thought I should try out some of Maya’s new features as well as the new cpu horsepower. Unfortunately there weren’t any obvious updates to the fluids system in this version as Bifrost, Xgen, and Bullet stole most of the thunder in terms of effects, but hopefully they will get some attention soon.

I spent a lot of time playing with various settings in the Contents Details, mostly in the density and temperature tabs. I wanted to achieve a flame from the exhaust that had slow burning fuel to give it a long life. Setting it’s ignition time to ignite slightly off the exhaust cone, and then using a higher ignition temperature, allowed the fuel to travel further before it was ignited. Most of the control came from the shading panel but adding lots of swirl and turbulence helped to sell the effect. I found it easiest to sim out a few frames and then render focusing on the alpha rather then the rgb values – you can always control the alpha in post but it complicates the gradient you get in the alpha at the end. Afterwards I went back to the rgb values and adjusted accordingly.

These sims had a base resolution of between 250 and 450 voxels in a 1 x 25 x 1 container size. In the past I’ve been nervous about surpassing the 3 million voxel limit which is around 150 x 150 x 150 in a 3D fluid container, but this surpassed this number with ease. I worked in the cm scale as I find meters to be very scene dependent and sensitive. At render time I used a global scale to push everything back to meters in order to render. Mental Ray has a tendency to exaggerate colors in a linear workspace when you render at an extremely small scale (I guess it could be a 1.8 cm rocket but it wasn’t what I had in mind…). If you noticed that it looks a bit like Wallace & Gromit’s rocket to the Moon, I always wanted to have a go at it.

Mental Ray’s update came with quite a few new features so I thought this might be a good time to check some of them out. The lighting is comprised of an old HDRI that I created in NZ, a directional light, and two area lights to fill in the bounce since there is no environment. The new unified sampling is really fast – motion blur, a typical post production RSMB task – didn’t seem so daunting when the time of the render didn’t triple. This is just one small object so I’ll bite my cheek on whether this holds true for larger scenes. The progressive mode was a great add too for IPR’s.


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