Ocean Simulation- or, Thank Goodness I Took Computer Graphics




OceanConstructor
Developer controlled settings


As I dove into ocean simulation, I remembered a joke we used to tell in undergrad computer science classes.  “We’re just coming up with increasingly complicated ways of being lazy.”  To avoid the tedium of manually animating water, I coded a model based on Gerstner waves.  Detailed in Mark Finch’s Nvidia’s GPU Gems chapter (linked here and below), Gerstner waves determine the horizontal and vertical shift of a point in space as a wave passes.  Summing the displacement of several varied waves produces a naturalistic undulation.

My current system in the Unreal Engine consists of three elements—a Blueprints ‘OceanConstructor’, a shader, and a C++ ‘OceanManager.’

The OceanConstructor class generates a dynamic material instance of the ocean shader, allowing for definition of parameters at runtime.  The developer chooses the number of waves to sum, the general wind direction, wave steepness, variation, and color of the ocean.  The Beaufort Scale setting determines wavelengths, speeds, and amplitudes based on an intensity scale from 1 to 12.

The shader, applied to a tessellated plane, uses a material function to determine and combine the physical displacement and normals produces by Equations 9 and 12 in the paper.  Panning normal maps add fine scale detail, and a simple Fresnel determines the color and influences the specularity of the water.

Gerstner Wave Material Function
It looks a lot nicer in C++.

The C++ ‘OceanManager’ class does the heavy lifting in terms of math.  It generates and stores specific parameters for each Gerstner wave based on the OceanConstructor’s general parameters.  It can calculate the height of a wave at any point in space, which the buoyancy model will later use to determine if an object is above or below water.

Wave Height Calculator
See?  So much nicer in C++.
There are plenty of tweaks and additional features I can return to in the future.  Adding more waves while optimizing the performance will create a more realistic appearance and reduce the effects of tiling.   Sea foam would add visual atmosphere.  I will additionally consider how to contain the water, whether in a more limited landscape or as an infinite ocean that follows the player.

Overall, I am quite happy with the results.  Despite being one of the hardest courses I had during undergrad, thank goodness I took Computer Graphics!

GPU Gems Paper: https://developer.nvidia.com/gpugems/GPUGems/gpugems_ch01.html

Comments

Post a Comment

Popular posts from this blog

Topology - A Continuous Learning Experience

Image
To avoid a spooky ghost crew, I modeled a man and woman with the same topology optimized for animation.  After initial studies in muscular structure and proportion, I dove into ZBrush.  I blocked out the body with ZSpheres and refined it with Dynamesh.  Between ZRemesher and classic arm-wrestling with Maya LT, I reduced the poly count down to about 10K quads for one character.  Depending on performance, I might reduce it further in the future. Because I approached modeling with the end goal of real-time animation, I wanted to create the best topology possible for smooth and clean deformation.  Each model since my first has been an experiment in topology, and I have used that experience with prior characters to create the current body. Body Topology The knees and elbows both have an extra edge loop on the outside corner of the joint.  Since these areas deform intensely, the extra geometry distributes weighting across the area and retains volume during deformation. The
Read more

Row, Row, Row Your Cube!

Image
When it comes to game development, the precursor of a sailboat is a sailcube! For buoyancy, I place a series of ‘test buoys’ around an object.  Each frame the object checks if those points are above or below water.  If significantly above, it applies gravity, and if significantly below, it applies upwards buoyancy.  If somewhat above or somewhat below, it applies a smaller force.  The result is an object that bobs and tilts with the water. Simple buoyancy When I implement the full ships, I will need to optimize each for the right balance of weight and ‘floatiness’.  This ultimately depends on the shape, mass, test buoy positions, and dampening.  I currently have an issue where the buoys do not account for horizontal displacement of the waves when determining if they are above or below water on steep waves, resulting in a momentarily floating ship or a ship that takes a little too long to rise with a wave.  I will test how significant this issue is on the full-size Vik
Read more

Let's Sail!

Chilled and drenched in rain after scrambling over rocks and stumbling through mud, I looked out over a rocky outcrop to the ruins of Dunscaith Castle on Scotland’s Isle of Skye.  Despite the impressive site, disappointment gripped me.  Centuries of history sat before my eyes, reduced to rubble by the elements and time.  What would someone standing in that same spot several centuries ago have seen?  Who lived there?  What did they do each day?  I walked away with unsatisfied curiosity and a desire to explore the now ruined castle.  In the back of my mind I thought, “Man, wouldn’t it be so cool to have a 3D model of that castle I could explore?” Fast forward several months, and here I am in Oslo with the Gokstad and Oseberg ships, the task of developing engaging virtual environments before me.  After several weeks spent up to my nose in articles and books about the burials, their context, and broader Viking Age society, I wondered how I could feasibly represent an environment that
Read more