During some downtime around the holidays, I had some fun createing this short Lego shot in Houdini. I wanted to wrap my head around some of the quirks of using Octane Renderer inside Houdini, as well as brush up on some RBD and Pyro simulation work.

I started with the explosion, because, well... it's fun to blow stuff up. I created a basic pyro sim, then converted the active voxels to points, transferred color info via the temperature attribute, and finally built a really basic system for copying lego pieces to the points. In my first pass at the system I used 5 lego pieces.

Once I built the basic system for turning volumes into Lego's, I couldn't help but keep pushing the system. It's far from perfect, but is more complex than I expected to be able to make. It copies about 6 pieces to the points created from the object, ranging from 2x4 to 1x1 pieces, taking into account orientations for the point groupings. I start by packing the largest possible pieces into the slices, then iteratively get smaller until there are only places for 1x1 bricks. 

I also felt that it would be important to have the animation not hit on every frame. I didn't want to do this in compositing, because though I felt the Lego animation should have a setppiness to it, a stop motion feel, I wanted the camera movements to be totally smooth. I was able to solve this easily with CHOPs. I apply this stepped curve to a Timeshift SOP for each element. This way I could have the explosion step at a 3 frame interval and the ships at 2 frame intervals, and have the camera animated each frame. The result adds a lot of interest to the scene.

Lighting and rendering was really quite fun. The models for the ships came from Mecabricks.com.

With a little VEX help from Aslak over on the cgwiki discord, I was able to use a few lines of vex to set prim color by using prim attributes from the imported materials, and then promote the color to a vertx attribute to refrence in the Octane material. I also wrote in per brick attributes for transmission weight, emission weight and color. In this way I authored one master material that worked with all the models.

Animating this was also a big challenge. Going through the process gives me so much more respect for the talented artists at the big studios. Choreographing the ships was step one, then framing, timing of the main shot, the RBD simulation of the tie exploding, adding in the swarms of ties and xwings, and also automating all their laser fire. There are just so many things to pay attention to when creating a shot like this. It's loads of fun, but loads of work. I'm glad I went through the process. Not bad for about a weeks worth of work.