The final result - Click to play

Intro

Ok, so it’s kind of hard to think of a clever title for a breakdown like this. Still, the shot is fun, so hopefully that’s enough!

Maya to RealFlow

The dynamic simulation after returning to Maya- Click to play

This shot begins it’s life in Google. I started by searching for photographs of cracked walls, stone, and glass, looking for a fracture pattern that I would like to replicate in my concrete slab.

When I found an acceptable pattern (broken glass as it turned out), I imported it into Maya as an image plane and set to work duplicating it’s pattern in geometry. To do this, I used the Create Polygon tool to create a face over one of the glass fragments, then used Append to Polygon to build out from there. The end result was a good match to the real-life fracture pattern, with each fragment of the real glass being copied by a face in my polygonal mesh. I then broke this apart into individual objects, extruded them to about an inch deep, and centered their pivot points. This was certainly the most tedious part of the shot, taking about 2 to 3 hours of mind numbing work, but it was incredibly easy and gave me a true-to-life fracture pattern for the concrete slab.

The bricks were simpler- I created a cube, rounded the edges a bit, and stacked them into a pattern behind the concrete. I then selected the bricks in the impact area and used Maya’s Solid Shatter to break them into random chunk- I wasn’t as concerned about their pattern being realistic since they’re behind the concrete slab. I also selected random bricks throughout the wall to fracture as well, to maintain a feeling a realistic randomness. These meshes were also center pivoted.

To get the models into RealFlow I exported as an .SD file using the plugin provided with the software, and it worked fine. Inside RealFlow I made all of the objects into Rigid Body dynamic objects and left their mass and other settings alone. I used the Attachator script from Dynamic Boy on the NextLimit scripting page to create Fixed constraints automatically to one key object. I then created a gravity field. The purpose of the Fixed constraint is to hold the wall chunks into their proper places as a wall until a certain amount of force is applied to them. The object that I attached them to I simply moved out of the way of the collision and turned off dynamics for, to prevent it being affected by the scene’s gravity. Next, I selected the constraints and set the levels of force that I wanted to apply to the break them apart from the wall- I had them much weaker in the center and progressively stronger as they reached the edges. I also set a release frame on the center constrains so that they would fall at a given frame even if they hadn’t been shoved aside- I didn’t want any individual faces still hanging around erroneously after a long simulation!

The particle dust in Maya- Click to play

Finally, I learned that it’s useful to select all of the objects and scale them from 1 down to 0.99 or so, preventing them from touching each other as soon as the simulation starts. This helps lessen the chance of errors, and you can simply scale them back to 1 when you export to Maya.

The actual explosion was simulated by slamming an extremely massive sphere into the wall. The final simulation ran over night, and had no problems. I used the propagation solver with time steps set to about 20. I then exported the .SD files back into Maya.

Finally, in Maya I used the original reference image of the fractured glass textured onto a plane as an emitter for cloud particles. I textured these with some noise, made them very transparent, and emitted a large number of them on each frame. I was only interested in the alpha channel, which I would use in AfterEffects to create the dust. I left the geometry on with a Use Background shader on it so that it would be properly occluded in the composite.

Render Passes and AfterEffects

In order to get the image I wanted in After Effects, I decided to render a depth pass, an ambient occlusion pass, a motion vector pass, and a beauty pass. For the 2Dmotion vector pass I used the LM2MV_v2 shader from La Maisson, allowing me to save significant Maya time by rendering the motion blur in AfterEffects using re:VisionFX’s ReelSmart Motion Blur plugin (I don’t go anywhere without it!)

In AfterEffects I simply pieced all of the various passes together and added some stylistic touches to make it look more “filmic” (or “muddy” in a less impressive term). I increased the contract in the color correction, and added a bit more blue and green. I added the explosion using stock footage from Detonation Films HD, which I luma matted. I added a bit of vignetting, and some vignette blurring, as well as a touch of optics compensation to fisheye the image a bit. I also added some light rays using Trapcode Shine, and some light wrap. Finally, I added a lens flare and some grain in Nuke (I like their lens flare and grain effects much more than stock AfterEffects- if you can afford Knoll’s Light Factory for AE it’d be perfect, but I don’t own it yet.)

The final beauty pass from Maya- Click to play

Depth map pass - Click to enlarge

Ambient occlusion pass- Click to play

Conclusion

The final result - Click to play

I decided to attempt this shot because I just bought RealFlow and was excited to explore it’s capabilities. One of the things I noticed quickly was that RealFlow has a fantastic rigid body solver, but I could find very few impressive examples of it in action. Having attempted shots like this previous in Maya, I knew what a pain it could be, and decided to see how RealFlow could handle it. The results were very impressive to me, especially given that I had literally just received my license for the software earlier in the week and had never used it before. With it’s strength and ease of use, I feel entirely confident that the program is capable of handling even the most complex rigid body interactions, and look forward to trying much more impressive shots in the future. Maybe a collapsing wall or tower for “Dragon Hunter II”…

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