FEELING HOT, HOT, HOT!
This was a little RnD project I was playing with over a few evenings.
The main goil of this shot was to see if I could reporduce the effect of lava running into the ocean and solidifying when it comes into contact with the hot water.
The basic setup is such that there is a flud wave tank which inherits the velocity from an overlaid ocean surface animation. Into this simulation I added several additional fluid sources. This gave me a starting point of water flowing into water.
From here I was able to start looking at making the secondary sources behave like Lava. This was initially done by adding viscosity to them. There are several apporaces you can take when trying ot make CGI lava. One of the main ones is to have the viscosity linked to the velocity. This works well in some cases and can produce a convincing effrect but it is a little circumstancial. If for whatever reason an area that is solidfitying speeds up again it then becomes more fluid.
I decided to go with a secondary technique where the viscosity is driven by a decreasing temperature attribute. Where the fluid starts hot and cools over time. The drawback to this is you can have a situaltion where the lava all tends to cool at one anc pile up. This can be nagated by having areas where the density lowest cooling faster as there are no neighbouring fluid particles to recieve heat from.
Once I had worked out a convincing setup for the lava I was able to start thinking about how to make the lava cool as it enters the water. I did this primarily by adding a temperature / heat attribute to the ocean simulation making it consistently cold. When the lava comes into contact with the water it cools, and therfore solidifies very quickly. It is still technically a fluid object, albeit a very thick one, which allows it to interacte with the ocean still, and sink.
To add to the effect I was able to isolate the cold areas of the lava and use them as a source for a small pyro simulation to generate steam.
In rendering, I drove the materials on the lava based on temperature. Where the hot areas glow almost white and transition through red to black as they cool. A nice little additon is to have a noise displacment on the very cold areas to give them a volcanic rock look.