As I planned to render the particles and Gaussian Splat separately I wanted to add the effect of the particles lighting up the environment. I did this by getting the transition particle band that was being used to spawn the particles and converted it to a VDB volume, this volume was then cleaned up and converted into a mesh, this allows for it to be procedural and change shape with the particles. The mesh is then used as an Octane Mesh light, the lights colour is also set to the average colour of the particles.
To add to this effect on the particle side, I used the age and life attributes. These are created when a POP sim is used and contain values related to how long the particle has been alive for. This data was then passed into the material where I could use it to multiply or set colour values.
My initial particle simulation used a POP wind and custom velocity. This velocity came from a cube made to be the same shape as the hallway, the normals of this cube were then converted to velocity attributes and used to push the particles away from the center of the hallway and stop them covering the center of the screen. I spent a long time with this setup and went through many iterations and research attempts to try and find my desired look. After focusing of other aspects of the project I went back to this, I found a technique of creating a simple pyro smoke simulation from an object the same shape as your desired effect, caching it, then using an addvecfield node within the POP network. This node imports the smoke cloud data into the particle simulation and adds the velocities to their nearest particles, making them behave in the same way as the smoke. Finally I added attribute blurs after the particle simulation, this try’s to blur and group the particles positions making the trails of particles appear more condensed and feel like they have forces clumping them together instead of being widely dispersed.
With this new setup, I had the look I was going for, but realised that the camera angle I had initially planned didn’t showcase this to its fullest. I decided to flip the camera and have it pulling back down the hallway, this allows the viewer to see more of the environment dissolving while also removing the issue of the particles obscuring the cameras vision.
I was having some issues with floating points and Gaussian Splats, so I went back into Postshot and cleaned up the Splat and reimported it into Houdini. As all of the processing on the points in Houdini is procedural, I didn’t need to change anything and it accepted the updated point cloud.