I joined BGSTR to develop an effect to transition from a fully CG cloth simulated flag to a flock of birds.
The effect was created in Houdini using a combination of POPs and VEX scripting. I scripted the bird behavior so as they "take off" they are lying flat on the flag surface and then slowly begin to orient toward normal flight. The birds inherited some velocity from the flag movement so if the simulation caused a snap in the flag's movement, the birds near the area would emit with some of that initial velocity. Once they were in flight, they took on the Craig Reynolds BOIDS emergent behavior, causing nearby birds to flock together.
The bird animation was created by the BGSTR team and exported to a short animation loop, which was instanced to each bird. Houdini's compiled blocks allowed me to instance hundreds of thousands of alembic birds with decent poly counts without losing too much performance. The system was extremely procedural and comfortably light.
The birds were later exported to Cinema 4D for lighting and rendering by the BGSTR team.