So to summarize:
1. If you use only object lights and V-Ray lights and you want caustics:
- enable GI caustics
- use good quality GI settings to make sure the caustics look sharp.
2. If you use max lights and
you want the light to pass
through refractive materials:
- use the affect shadow
option for a fake caustic
effect
- OR enable caustics in the caustics rollout and play with the settings for photon mapped caustics.
3. If you use V-Ray lights and you want photon mapped caustics:
- Disable affect shadows
- Disable GI caustics
- Enable caustics in the
caustics rollout and play
with the settings.