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| m_Name: Ocean and Environment |
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| m_overrideMarkdownText: "# Ocean Design and Implementation\n\nThe ocean system |
| uses an inverse Fast Fourier Transform (iFFT) to simulate realistic wave motion |
| across many waves (128\xB2 = 16,384 waves at default resolution). This method |
| provides detailed, dynamic ocean visuals while maintaining performance.\n\n\n\n## |
| Choosing iFFT Over Gerstner Waves\n\nEarly tests with Gerstner waves in the vertex |
| shader were inefficient for realistic ocean simulation. While suitable for stylized |
| games, Gerstner waves require individual control over direction, amplitude, and |
| wavelength, making them hard to manage and computationally expensive at high |
| wave counts. In contrast, iFFT generates a frequency spectrum of waves, offering |
| greater realism and easier control.\n\nAlthough iFFT can be computationally expensive, |
| optimizations ensured it remained viable. A key decision was whether to run the |
| simulation on the CPU or GPU. The GPU is well-suited for parallel processing, |
| but the project required high frame rates and high-resolution rendering, making |
| additional GPU load undesirable. Moreover, ocean height queries for floating |
| objects and ship physics would require costly GPU-to-CPU data transfers. To address |
| these concerns, the simulation runs on the CPU, leveraging Unity's job system |
| and Burst compiler for parallelized, optimized calculations. Certain iFFT components |
| update only when parameters change, further reducing CPU load.\n\n## Environment |
| Profile & Ocean Settings\n\n\n\n1. **Wind Yaw/Pitch**\n\n |
| Controls the wind direction and, consequently, the ocean waves. Instead of a |
| full XYZ rotation, pitch and yaw suffice to control wind direction, converted |
| to a vector via spherical coordinate transform. The ocean does not react to up/down |
| wind, but other effects, like sails, do. The total projected length of the wind |
| vector along the ocean plane is used as the final wind speed/direction for the |
| ocean simulation. Wind speed is set specifically for the ocean, independent of |
| other systems, for more control.\n\n2. **Wind Speed**\n\n Controls the strength, |
| speed, and height of the waves. Higher speeds cause larger, choppier waves, while |
| lower speeds produce gentle waves.\n\n3. **Directionality**\n\n Controls wave |
| alignment with the wind direction. A value of 0 gives a random, choppy look, |
| while 1 aligns most waves with the wind. Very low or high values are most useful |
| for random or windy scenarios; in-between values give a non-specific look.\n\n4. |
| **Choppiness**\n\n Controls horizontal wave displacement. Simple up/down movement |
| is insufficient for a convincing ocean, so extra horizontal displacement is calculated/applied |
| to the vertices. This value generally looks best at 1 but is included for flexibility.\n\n5. |
| **Patch Size**\n\n Defines the world-space size the ocean simulation covers. |
| Simulating an infinite ocean is not feasible, so a small patch is simulated and |
| repeated over the ocean surface. Smaller values concentrate detail in a smaller |
| area, but tiling may be more noticeable. Larger values reduce repetition and |
| allow for larger, varied waves, especially with higher wind speeds, but lose |
| fine detail. A detail normal map can restore some fine detail. A scrolling noise |
| texture modulates displacement to break up tiling.\n\n6. **MinWaveSize**\n\n |
| A fine control filter to fade out very small waves generated by the simulation. |
| At lower resolutions and patch sizes, small wavelengths can alias, causing a |
| faceted or flickering look. It can also be used for a stylized look, removing |
| finer waves and leaving larger rolling waves.\n\n7. **(Advanced) Gravity**\n\n |
| Earth's gravity in meters per second controls the relation between wave size |
| and speed. Generally, this should not be adjusted as it can make waves look oddly |
| fast or slow, but it is included for special cases.\n\n8. **(Advanced) SequenceLength**\n\n |
| The sequence repeats after a certain time to avoid accumulating floating-point |
| errors. It can be shortened to produce a looping sequence, e.g., a 10-second |
| loop baked into displacement/normal maps to avoid runtime computation. Larger |
| waves will not progress correctly at short sequences. For most cases, set this |
| to a high value, like 200 seconds, to reduce errors without noticeable repetition.\n\n9. |
| **(Advanced) TimeScale**\n\n Scales the simulation speed. Usually left at 1, |
| it can slow down or speed up the simulation or achieve certain ocean states/looks |
| not possible with regular controls. However, other controls should be used instead, |
| as this parameter often produces unrealistic results.\n\n## Ocean Simulation |
| & Material\n\nThe material used for rendering the ocean can vary per environment |
| profile. The system smoothly transitions between different materials/parameters |
| when profiles change. Care is needed as texture properties can't be interpolated, |
| and certain parameters, like changing time scales or texture scaling/offsets, |
| can cause large changes during transitions. More details are in the Ocean Shader |
| section.\n\n## Ocean Simulation\n\nThis component updates the ocean simulation, |
| setting up data for burst jobs, dispatching them, and updating the final texture |
| contents. It dispatches a job to fill the ocean spectrum data when ocean properties |
| change, like wind speed or direction. This fills an n*n resolution array with |
| float4's containing two complex numbers, representing initial wave properties |
| like amplitude and frequency. It also fills a dispersion table buffer with initial |
| time-related properties.\n\nEach frame starts with a dispersion job update, initializing |
| a complex number array for the height component and two additional arrays for |
| X and Z displacement components. These are inputs into the iFFT jobs, processed |
| in groups targeting an entire row and then an entire column of the texture.\n\nThe |
| final result is written to the displacement texture using GetRawTextureData to |
| write directly to the pixel data without requiring copies/conversions. This is |
| an RGBA 16-bit float texture; the alpha channel is unused since there is no signed |
| float texture format with only RGB channels. An unsigned texture could be used |
| with a bias, but precision close to zero is essential.\n\nA second pass generates |
| a normal/foam/smoothness map based on the displacement data. Normals are computed |
| via the central difference of four neighboring displacement samples. Foam at |
| wave peaks is calculated using the Jacobian of the displacement. The final value |
| is processed in the shader according to foam threshold and strength parameters.\n\nThe |
| alpha channel stores a filtered smoothness value, helping with consistent highlights |
| and environment reflections in the distance. It's calculated by averaging normal |
| length and mapping it to a roughness value via analytical importance sampling |
| of a GGX distribution.\n\n**Normal Map Baker**\n\nA function, accessible via |
| a context menu option (right-clicking on the OceanSimulation component), bakes |
| the current ocean's normal map into a texture. This can be used as a detail normal |
| map in the ocean material or for other purposes. Increasing simulation resolution |
| and adjusting properties can capture smaller-scale details in the normal map |
| while leaving the ocean simulation to calculate larger-scale details and displacement.\n\n\n\n## |
| Quadtree Renderer\n\nThe ocean uses a Quadtree system for rendering instead of |
| a single mesh like a plane. This approach balances vertex density and draw distance. |
| The system moves with the camera, ensuring the ocean is always visible.\n\n\n\nEach |
| frame, the quadtree aligns with the camera position based on a grid size, set |
| to the vertex spacing of the largest subdivision level. This prevents mesh sliding, |
| which can cause artifacts as the camera moves. The highest quadtree level is |
| checked against the camera view frustum. If visible, it is evaluated for subdivision |
| based on its distance to the camera, multiplied by the current quadtree level's |
| radius. If below a threshold, it subdivides, and each child patch is checked |
| against the view frustum and tested for further subdivision if visible.\n\nVisible |
| patches that are not close enough for further subdivision, or have reached the |
| max subdivision level, are added to a rendering list.\n\nPatches are grouped |
| into draw calls based on subdivision levels. If all neighbors share the same |
| level, a simple tessellated quad is used. Otherwise, an index buffer with edge-stitching |
| prevents seams between meshes. All patches use the same vertex buffer for performance |
| but different index buffers.\n\nThe final draw calls are rendered using Graphics.DrawMeshInstanced.\n\nEfforts |
| to use displacement map LODs for smoother transitions between LODs were explored, |
| but time constraints prevented full implementation. Issues with cracks between |
| patches and performance concerns due to extra data processing remain.\n\nThe |
| system is controlled by several parameters:\n\n- **Size:** Total patch size, |
| ideally large enough to reach the far plane in all directions. Balances processing |
| needs and detail up close. Avoid excessive size. Techniques like fog can hide |
| the ocean disappearing at a distance.\n- **Vertex Count:** Number of vertices |
| along one side of a patch. For example, a value of 8 creates a patch with 8*8=64 |
| vertices. (Actual count is N+1 to form a quad with N*N patches.)\n- **LOD levels:** |
| Maximum grid subdivisions. Subdivision level depends on camera distance, with |
| higher levels offering more detail up close but requiring more processing.\n- |
| **Max Height:** Corresponds to wave height in world space, used for culling patches |
| below the camera.\n- **Culling Bounds Scale:** Patches are culled based on a |
| bounding box. High wind speeds can cause patches to disappear while still visible |
| due to horizontal and vertical displacement.\n- **LOD threshold:** A patch subdivides |
| into smaller patches when closer to the camera than its radius multiplied by |
| this threshold. Increasing this value reduces flickering/popping as the camera |
| moves but increases GPU vertex processing.\n- **Skirting Size:** Beyond the ocean |
| distance, a simple \"skirting mesh\" renders more of the mesh with simplified |
| geometry. No LOD-stitching means minor cracks may appear. Best used if rendering |
| the ocean to the far plane is too demanding.\n\n## Conclusion\n\nBy using iFFT, |
| CPU-side processing, and a dynamic quadtree renderer, the ocean system achieves |
| high visual fidelity while maintaining performance. Future improvements could |
| include smoother LOD transitions and optimizations for GPU-based displacement |
| rendering.\n\n### Relevant Files\n- [OceanSimulation.cs](https://github.com/meta-quest/Unity-UtilityPackages/blob/main/com.meta.utilities.environment/Runtime/Scripts/Water/OceanSimulation.cs)\n- |
| [OceanSpectrumJob.cs](https://github.com/meta-quest/Unity-UtilityPackages/blob/main/com.meta.utilities.environment/Runtime/Scripts/Water/OceanSpectrumJob.cs)\n- |
| [OceanDispersionJob.cs](https://github.com/meta-quest/Unity-UtilityPackages/blob/main/com.meta.utilities.environment/Runtime/Scripts/Water/OceanDispersionJob.cs)\n- |
| [OceanFFTRowJob.cs](https://github.com/meta-quest/Unity-UtilityPackages/blob/main/com.meta.utilities.environment/Runtime/Scripts/Water/OceanFFTRowJob.cs)\n- |
| [OceanFFTColumnJob.cs](https://github.com/meta-quest/Unity-UtilityPackages/blob/main/com.meta.utilities.environment/Runtime/Scripts/Water/OceanFFTColumnJob.cs)\n- |
| [OceanFFTFinalJob.cs](https://github.com/meta-quest/Unity-UtilityPackages/blob/main/com.meta.utilities.environment/Runtime/Scripts/Water/OceanFFTFinalJob.cs)\n- |
| [QuadtreeRenderer.cs](https://github.com/meta-quest/Unity-UtilityPackages/blob/main/com.meta.utilities.environment/Runtime/Scripts/Water/QuadtreeRenderer.cs)\n" |
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