Solution to problems with secondary bounces in V-Ray
Working with V-Ray and 3ds Max on interior animations can be a challenge, especially when it comes to indirect lighting. A common problem is that, when loading an irradiance map from file and using Quasi Monte Carlo (QMC) for the secondary bounces, the render may come out dark or without the expected indirect lighting. And no, it's not that the lights have decided to go on vacation! 💡
Why does this happen?
The precomputed irradiance map works very well with Light Cache, as it is generated as a global process that saves cumulative information from the scene. This allows the secondary bounces to be interpreted correctly throughout the entire animation. However, with Quasi Monte Carlo, which calculates the secondary bounces in a more direct way and without a global cache, the system cannot take advantage of a pre-recorded irradiance map. This is because the secondary bounces must be calculated in each frame.
If you load the irradiance map but leave QMC for the secondary bounces, the indirect lighting is incomplete and the scene looks dark. It's as if V-Ray decided to turn off the lights just when you need them most. 😅
How to fix it
For animations with irradiance maps from file, the recommendation is to use Light Cache for the secondary bounces, ideally in Flight Through mode. This mode generates the cache only once and reuses it, speeding up the render and avoiding flickering.
If Light Cache fails or saturates in heavy scenes, try these options:
- Increase RAM memory or adjust the Light Cache parameters (reduce subdivisions, use filters or change the mode to Single frame to test).
- Divide the scene into smaller parts to avoid saturating the cache.
- Update V-Ray and 3ds Max to the latest versions to take advantage of stability improvements.
If you can't use Light Cache, you'll have to give up using the pre-recorded irradiance map and use Quasi Monte Carlo for the secondary bounces, calculating them in each frame, although it is slower.
Remember, in the world of rendering, patience and experimentation are your best allies. And always keep a backup!
So now you know, with these techniques, you can solve the problems with secondary bounces in V-Ray and achieve the indirect lighting you seek in your animations. And remember, if the light disappears, you can always blame the digital ghosts! 👻