Snow problem!
I’m getting quite good at using houdini’s pyro tools for things like explosions, rocket exhausts and debris / dust but I wanted to try my hand at creating something on a massive scale such as an avalanche.
I started by creating a relatively basic terrain setup on which the avalanche would flow down, this was done using the built in terrain tools in Houdini. I wanted it to look realistic, but not be the entire focus of the project. For this one I really wanted to work on the avalanche effect. I could always come back and refine the terrain later once I had the main technique down.
Avalanche Simulation
The avalanche simulation itself was created in a number of steps. I’ll outline the general process here but slightly further down the page I’ll add some images to illustrate the steps.
Firstly I created a particle simulation that falls down the mountain as a guide for the source of the avalanche. Another approach could have been to create a single source of pyro at the top and create a system to force it down the mountain but I felt this approach was more true to life and a little different to what I’ve been able to achieve before.
These particles transferred a colour attribute to the underlying terrain as a visual guide. This also gave me the ability to isolate the areas which they interacted with in order to drive the avalanche smoke simulation.
The guide areas were converted into a smoke source which inherited the velocity of the original particle simulation to get the smoke moving down the mountain.
Because the effect is quite far away from the camera I was able to keep the amount of detail quite light, reducing simulation and ultimately rendering time.
In the images above you can see the basic terrain layout. On the left is the entire terrain geometry and on the right is the region I isolated to be used as a collider in the simulation.
The four images above show the process of generating the avalanche effect.
The particle simulation to drive the generation and the velocity
Transferring the particle information onto the terrain
Rasterizing the above area in preparation for the main simulation
The final result of the avalanche sim
Setting the scene
I generated some clouds using the typical Houdini tools and scattered them along the tops of the mountains to break up the skyline and give the avalanche a kind of “reveal” as it emerges from the top.
The trees were scattered over the mountains driven by a random noise pattern and restricted to areas that aren’t too steep to keep their locations believable. They also were incredibly helpful in creating the sense of scale to the scene as without them it was a little tricky to gauge just how big everything is.
I’m currently updating this scene with a different variety of trees and a more detailed avalanche and longer avalanche simulation. Watch this space! (I’ve added a little WIP frame below)
As always, a tidy scene file, is a happy scene file!