Underwater caustics play a crucial role in making ocean and pool scenes look realistic. In most examples found online, caustics are generated using light textures, which often result in sharp shadows that don’t behave naturally in moving water.
In this test, I explored a different approach—simulating caustics dynamically instead of using a pre-made texture in the light source. This method provides softer, more natural shadows. While the result is promising, there’s still room for improvement, especially in making the caustic texture feel more dynamic over time.
💡 How I created underwater caustics in Houdini:
✅ Step 1: Generated a wave simulation as the base water surface.
✅ Step 2: Placed particles on the waves and locked their positions to avoid flickering.
✅ Step 3: Rotated particles based on wave normals for accurate refractions.
✅ Step 4: Used light reflection techniques to generate caustic patterns.
✅ Step 5: Converted the caustic effect into a looping texture (250-frame loop).
✅ Step 6: Downloaded free underwater models from Sketchfab and rendered in 3ds Max + V-Ray.
✅ Step 7: Combined a normal render with the caustic shadow pass using VRayRawShadow for softer results.
🔹 Problem: Most online methods generate caustics using light textures, which produce harsh, unrealistic shadows.
✔ Solution: Instead of relying on a single caustic pass, I rendered two separate versions—one with caustics and one without caustics—and blended them using VRayRawShadow. This approach softened the caustic shadows, making them more natural and less harsh.
🔹 Problem: The caustic texture lacked a strong sense of motion when the water moved.
🚀 Next Steps: Further refining the caustic texture animation to make the light patterns feel more organic.
This experiment proved that dynamic caustic generation can create more natural-looking underwater lighting effects compared to standard light texture methods. However, improving the fluid motion feel in the caustic texture remains an open challenge for future iterations.”