MLT BiDir vs Path BiDir

[contegufo]

Hi

The two images have the same calculation time (19h) but is a winner already after 4h the MLT with Bidir.
Even eye could see a faster speed. I do not know if continuing rendering would become equal; I do not believe!
The materials are glass and chrome of home or a business so no exasperation with reflective materials.
Supersample=5

[Oscar J]

Do you have Arch Glass materials, or just normal glass? It is VERY important to use Arch Glass when you have big, flat windows where light should enter. I'm almost certain that this is the reason for simple BiDir performing worse.

Fix that and try BiDir again.

[contegufo]

Hi

The tests involve intricate because different versions of Cinema and different versions dell'exporter.
Upgrading to all versions of the Cinema exporter latest and activating the option Arch Glass the results are correct.
I launched three rendering for the three versions of Cinema (R13 / R15 / R17) since the current deficit dell'exporter Mac is the limit of a single instanced time.
You were right, thank you!

[Oscar J]

Just a tip: single face arch glass is just supposed to be used when your glass doesn't have any thickness. Otherwise arch glass is a better choice.

[Zom-B]

Hey contegufo,

why don't you activate your C4D exporter version?!

[Silverwing]

Hi There. Here are just my two cents:

Different algorithms are better for different situations! The User has to know the strength and weakness of every one of those and use them to the best!

You choose different calculations methods based on what light is doing in your scene!
Its not the programmers fault if Unidirectional Pathtracing performs purely with caustics and interiors with small indirect light sources.

Btw. the algorithms used in Indigo are all unbiased (for now). Meaning that there is a statistical prove that with enough time they will converge to the perfect noise free unbiased image. But that does not mean that everything thats called unbiased is efficient!

While Pathtracing performs really fast in open scenes with big Light sources and only little transparent materials Metropolis Light transport would perform purely because the chance of reaching a light source is really high.
Its the other way around with closed rooms with small indirect light sources and a lot of glass. In such situations Patchtracing performs purely because the light sources are not directly seen and the chance is really low to "brute force" reconstruct a light pass. Therefore MLT works much better.

The key is just to lean the principal behind the algorithms and learn what they are good for. I do not understand all the math behind this too. But as user this is not necessary. Its always good to have a basic understanding of whats going on behind the scenes of a renderer so you can avoid problems and solve eventual errors.

P.s. if you are really interested take this course here:
TU Vienna Raytracing Course

Cheers,
Raphael

[contegufo]

Hey contegufo,

why don't you activate your C4D exporter version?!

Currently 3.8.26
Before 3.6.24