Reactive Foam for Psunami

Overview: The Psunami Plug-in from Northern Lights offers the ability to create realistic ocean and water simulations. It however lacks the ability to generate foam on the surface of an ocean. I developed the following technique to create foam on the surface peaks of the plug-in.

How it works
The technique is very simple. It involves mapping a simple gradient to the side of the plug-in object and using a reactive shader to generate the foam on the white (High) areas of the ocean surface.

What you will need... - Psunami, Photoshop, and a reactive shader (I used Mondo FBlocks from Agrapha). - Adobe After Effect - Lots of pictures of oceans for visual reference.

Step 1: Add a new psunami object to your scene. Set the wind speed to be high enough to see some dramatic peaks. Foam is usually formed in rough seas where the waves are constantly breaking or where a wake is formed by a boat. Add the Ocean optics shader and setup up the surface optics of the object as you would according to the Psunami documentation. This will be our base ocean.

Step 2: Duplicate the Psunami Group and call it "Psunami Foam". This will act as our foam surface.

Step 3: In Photoshop you need to generate a standard gradient of 512 x 512 pixels that graduates from white to black, top to bottom. Save this file in Electric Image format and call it something like "OceanGrad.img".

Note: You can use a ramp shader instead for a greater range of control over the reactive surface break up.

Step 4: Apply the "OceanGrad" to the diffuse channel of the 'Psunami Foam' Object. Open the texture editor and set alignment to front.

Set the texture projection to 'Front'
	The scaling of the shader should be set to 100 in the X, Y and Z channels.

Mondo FBlock settings This screenshot shows my settings for the AG Mondo F Blocks shader. I used this shader because it allows fine control over the intereaction of the shader with the reactive map.

Step 6: The foam will appear to be automatically animated. This is due to the fact the geometry is effectively moving through the shader. The speed of the animation is controlled by the Y scale of the shader. The further the shader is stretched in the Y axis (World Coordinate) the slower the foam movement.

Step 7: Turn the specularity of the Psunami geometry off by setting the value to 0. We will composite the foam as a separate pass in After Effects using the screen function.

Step 8: Render the scene.

You should now have a foam pass that looks similar to this
Step 9: Render out the Original Psunami object to create your standard ocean color pass.

Step 10: In After Effects Create a new composition and place both the Color Pass and the Foam pass into it. Ensure that the 'Foam Pass' is the top layer and set it's layering mode to screen.
Voila! To create more realism tweak the colors and levels of the foam pass to match any of your ocean reference photos.

Notes on Wakes: Boat wakes can be created by simply creating a greyscale map that approximates the size of the ship and the spread of the wake. This can be a very simple map. This map is then applied directly above the 'OceanGrad' map using the 'Screen' layering mode in the texture editor. You may animate the position of the wake map to match the object that is creating it.

Enjoy!

Matt Drummond

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