Hi everybody,
Is it correct to simply put a local forward vector on the quad of the particle for his normal to have proper lighting calculation or more magic is needed to have proper good quality results?
Thanks!

It would depend on the particle type (smoke, fire, etc) I suppose. I can think of a few options:

• vertex normals perpendicular to particle billboard. This would probably look very flat.
• I could also imagine using “bent”/sphere vertex normals that are not perpendicular to the billboard, so that the particle could seem more rounded rather than flat, without the need for normal map.
• vertex normals perpendicular to particle billboard, with additional tangent-space normal map. This is probably the best way to get good quality particle lighting.