Lighting power issues

Hi everybody, sorry for the vague title, if after reading anybody have a better one i’ll be happy to change it.

So here’s the deal.
I’m working on an interior scene, i have sun lamp (multiple importance sampling on) some meshes with emission shader out of the windows (uncheckd ray shadows to let the sun came in).

Until here all good, then i had to add 33 point lamp for some appliques on the walls and suddenly the sun is no longer visibile…it’s like if it’s power has been set to some very low value like 0.1, very weak results. If i turn off the point lights layer all come back to normal.
I figured out that’s related to the number of the point lights. If i add some few ones like maybe 5 it’s still good but the more there are the more the sun power, or for better saying, the sun result goes down.
I belive that with something like 3 to 6 to 8 point lights this issues is already in, it’s just it’s not that noticeable.

I’ve thought that it might be depends on the clamps values that were set to 10 and 10 but i give a shot with them at 0 and still the same.

Any idea? is that a sort of a bug?

Thanks in advance

There is a concept called “Energy Conservation” where , in theory, only so much energy exists in the scene. To add the 33 point lamps you need to think of their total contribution to the scene. If the Sun contributes 1.0 to the scene and you want the 33 lamps to take on 20% of that lighting role then the sun should be reduced to 0.8 and the the remaining 0.2 should be divided between the 33. Thus 0.2/33.0 is the intensity of each point lamp.

An easy way to manage this in Blender is to make each of point lamps an instance then when you change the values of one, they all inherit that value and all other settings for that lamp type.

This was a problem of Sampling all lights feature deactivated (Path tracing integrator doesn’t have it). I spoke with him privately and switching to Branched and use sample all light solved the issue.

I had the same problem, i had strong sun coming into the room, when adding tens of spots, sun just vanished…the problem we face in archiviz though is that branched isn’t that beneficial, takes more memory and is quite slow, since there is not a strong dominance of either diffuse, glossy, transmission, mesh lights…we “always” has a mixture of every shader in the shot, and thus using simple Path tracing is often better and quicker. Yes you probably need more samples, but you can forget about tweaking samples etc…

Example: interiors are difficult for light bouncing around, so >> high diffuse samples
Every shader has some sort of glossy coat (floor, walls, props…) >> high glossy samples
Glasses/transmissions are nearly always present (props, kitchens, windows, curtains) >> high transmission samples
SSS could stay low most of the times unless you want a “super real” marble, or you have lots of candles :slight_smile:
Invisible Mesh lights are of great help near windows and to fill dark areas >> high Mesh light samples…

Cranking up everything makes little sense for branched, then using PT…but many many times in interiors we have lots of spot lights, simple PT does not have “sample all lights”…then what? :confused: Cycles isn’t interior friendly as it is now, sadly. (i mean, is it a great engine, but it’s clear that the development had not considered this field as a candidate for the engine guidelines or its design…)