Week 3 – Particle Instancing

This weeks dynamics homework exercise
revolves around particle instancing. Building on the ‘rock explosion’ knowledge we gained in class, the direction was to take a supplied model of a bi-plane and build a shot to a very specific brief using particle instances.

The key requests in the brief are as follows –

– Create a squadron of planes flying through the air.
– Exactly 72 planes.
– moving towards the camera (supplied) over the course of 100 frames.
– Each to have a unique motion.

Firstly, I knew that for the instances to be facing the correct direction in the final simulation, that the ‘hero’ geometry must be facing in the positive X direction. So I rotated the plane to face positive X and froze the transforms. One complication of this is that I needed to re-do the propeller rotation as it was now rotating in X, not Z.
With the grouped instance ready to go, I created a cube volume particle emitter, then set up the bi-Plane group to be the instanced object in the instancer window.

Hitting the play button now creates plane instances mimicking the movement of the particles. Obviously many changes had to be tweaked in the settings

Emitter settings –
Key things to note for emitter settings-
– a rate of 100 i.e – not emitting too quickly so that they have a nice seperation between then, not too bunched.
Zero for ‘away from center’, we will use fields to control the action.
1 in the ‘along axis’ setting (which is like a speed control for volume emitters) – I was not too fussed by this as further speed control would by added with a uniform field.

Particle shape node attributesparticleShapeAtt

key things to note here –
max count to 72 to cap the number of instances
live forever, we don’t want planes disappearing
aim direction set to velocity so that the planes tilt in the direction of the momentum

For the additional motion, I created a uniform field to drive the planes forward and control the speed. I set the magnitude to 5 in the direction of X.

For the random bumpiness, I created a turbulence field. I set the magnitude to 20 and the frequency to 15 which created about the right kind of subtle movement.

Finishing touches-
I unlocked the render cam and tweaked the angle so that a plane would come really close to the camera right at the end of the sequence (whoops, not sure if we were supposed to do that?)
I mapped the image plane to a cylinder and positioned it where it cover the field of view from the render cam.
I assigned a simple blinn material to the original plane. I wanted to get carried away and set up a shading network but then I realized that the plane did not have correct UV’s so I decided against it.
Then I rendered with mental ray, my choice really came down to wanting to experiment with the motion blur settings. I had alot of problems with render settings as it was the first time I have used 2014 for rendering and did not quite have my head around the new unified sampling settings.
I rendered one sequence with motion blur and one without to see the difference. In the end I comped the two sequences together in nuke with a merge over node. This was a comp cheat to reduce the amount of ‘chattering’ from the motion blur – here is the final result


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