In the first post on ray-traced caustic effects, we introduced mesh caustics and its usages in Unreal Engine 4. In this second post, we describe water caustics.
Overview
This article discusses the implementation of ray-traced water caustics in Unreal Engine 4, detailing the advancements made since the previous post, particularly focusing on water caustics. It covers the basic workflow, various techniques for generating caustics, and performance considerations.
What You'll Learn
1
How to implement ray-guided water caustics in Unreal Engine 4
2
Why using cascaded caustic maps improves performance in large scenes
3
When to choose between photon difference scattering and procedural caustic mesh techniques
Prerequisites & Requirements
- Understanding of ray tracing concepts and Unreal Engine 4
- Access to Unreal Engine 4 and NVIDIA RTX hardware
Key Questions Answered
What are the steps to implement water caustics in Unreal Engine 4?
To implement water caustics, you need to render water surfaces into caustics maps, generate rays from these maps, render caustics into a buffer, and perform denoising. This process allows for realistic caustic effects in scenes with water.
How does photon difference scattering improve caustic rendering?
Photon difference scattering improves caustic rendering by treating ray hit points as photon footprints, allowing for better intensity distribution and detail in caustic patterns. This method uses sparser rays to maintain quality while enhancing performance.
What is the advantage of using procedural caustic meshes?
Procedural caustic meshes provide sharp caustic patterns even with low caustics map resolutions, making them efficient for large water bodies. They allow for quick rendering and can be adjusted based on scene requirements.
What performance metrics are associated with water caustics rendering?
Water caustics rendering typically takes less than 13% of frame time, with costs ranging from 0.5 to 2 ms depending on the GPU. Both photon difference scattering and procedural caustic mesh methods have similar performance costs.
Key Statistics & Figures
Caustics map resolution
1024x1024
Used in the swimming pool scene for performance testing.
Frame time for water caustics
0.5 to 2 ms
Expected cost of water caustics rendering on different NVIDIA RTX GPUs.
Percentage of frame time taken by water caustics
less than 13%
This applies to all test cases involving caustics rendering.
Technologies & Tools
Game Engine
Unreal Engine 4
Used for implementing ray-traced caustics effects.
Hardware
Nvidia Rtx
Required for ray tracing capabilities in Unreal Engine.
Key Actionable Insights
1Utilize the photon difference scattering method for detailed caustics in smaller water bodies like pools.This method provides flexibility and supports area lighting, making it ideal for confined spaces where detail is crucial.
2Implement cascaded caustic maps to enhance performance in large scenes with extensive water surfaces.Cascaded maps allow for distributing more photons in closer areas while reducing the number in distant cascades, balancing quality and performance.
3Choose procedural caustic meshes for sharp caustic patterns in expansive water bodies.This approach minimizes performance overhead while ensuring high-quality visuals, especially in large environments like oceans.
Common Pitfalls
1
Using a low-resolution caustics map for large scenes can lead to blurry caustic patterns.
This happens because the detail captured in the caustics map is insufficient for the expansive area, resulting in a loss of visual fidelity.
2
Not adjusting the caustics map resolution based on scene size can impact performance.
Higher resolutions increase the number of photons processed, which can slow down rendering if not matched to the scene's requirements.
Related Concepts
Ray Tracing Techniques
Water Rendering In Games
Performance Optimization In Graphics