Why small emiters take to long to render?

[jp_vas]

Hi everybody, i tried to find an answer of my question in the forums but i could not find it, y hope octane team or some expert can help

i am working in an interior scene that has 6 small lights (about 8cm diameter) they are placed below the lighting fixture and they are not intersecting any object. Also the normals are oriented correctly.

When i turn on this small lights the render time increases a lot more (also the noise) compared when i use big emiters (about 1m x 2m)
what is happenig? why that big time diference betwen the to emiter sizes?

note: im not turning on all the emiters (small and big) to check the diferences.

i have another question, is the power and efficiency (0.025) of the blackbody emiters reflecting real life behavior? what is the power slider unit?

thank you very much for your time
JP

[t_3]

the power slider unit is watt.
efficiency tells, how much of that energy is distributed as visible light; i.e. a common indascent 100w light bulb distributes only 2,5% as visible light, therefore the default setting is 0.025 (matching the power default auf 100 watts). http://en.wikipedia.org/wiki/Incandescent_light_bulb
to reduce noise with small emitters, use the sample_rate parameter of the emitters (higher values means more samples created by them).
this thread http://www.refractivesoftware.com/forum ... 39&p=72421 explains a little about the background...

[jp_vas]

Thank you very much for the soon reply

so to reduce the noise with small emiters should INCREASE or DECREASE the sample_rate parameter of the emitters?
more samples equals more noise?

will this be fixed in future releases?
thx keep the good work Octane team

[gabrielefx]

Thank you very much for the soon reply

so to reduce the noise with small emiters should INCREASE or DECREASE the sample_rate parameter of the emitters?
more samples equals more noise?

will this be fixed in future releases?
thx keep the good work Octane team

no,
more samples = less noise
but if you have in your scene 3 emitters only with the same size and no other emitting sources then the sample rate will not work.
Sample rate works only if you have in your scene emitters with different size. For example one large panel and tiny emitters.
You have to balance manually all the lights according to the sizes.
In the next release this feature will be automatic

[KaroBastardKiter]

In the next release this feature will be automatic

thank god for that

[jp_vas]

thanks gabrielefx for the useful information.

what happens in my case that i have 6 small emiters (8cm diameter) and no big emiters? do you think sample_rate can work to reduce noise? because there is a lot of noise with those emiters only, so y tried turning them off and using a small wall panel as an emiter (about 0.6mx2.4m) and when i turn it on the scen is lit and it has very little noise...

also i think this sample_rate parameter is not present in the 2.52 version... i will try with the new release candidate.

In the next release this feature will be automatic

good to hear, i think this really should be fixed for working in archviz because its kind of annoying

thx

[t_3]

what happens in my case that i have 6 small emiters (8cm diameter) and no big emiters?

and no enviroment also?

[jp_vas]

it was my mistake, yes the problem comes when using diferent size emiters... it seems that i didnt turn one of the emiters slider all the way down... but as i choose null emission it was ok.

you asked about the environment, i was using the default texture emision with power = 1, if i am not using the environment should i use a value = 0 for power. or it doesnt matter?

[t_3]

it was my mistake, yes the problem comes when using diferent size emiters... it seems that i didnt turn one of the emiters slider all the way down... but as i choose null emission it was ok.

you asked about the environment, i was using the default texture emision with power = 1, if i am not using the environment should i use a value = 0 for power. or it doesnt matter?

afaik you can't turn power down to zero, only distribution can be set zero - what should effectively turn the emission off.

but if you use an (active) environment emitter, you already combine one large with misc. small emitters

i usually keep emitters in external mats or macros, and just disconnect them. imo the fastest and most secure way to turn a light off (and doesn't need to change values also); if i need to hide the emitting object, i just connect a portal (turned off) instead...

[gabrielefx]

it was my mistake, yes the problem comes when using diferent size emiters... it seems that i didnt turn one of the emiters slider all the way down... but as i choose null emission it was ok.

you asked about the environment, i was using the default texture emision with power = 1, if i am not using the environment should i use a value = 0 for power. or it doesnt matter?

afaik you can't turn power down to zero, only distribution can be set zero - what should effectively turn the emission off.

but if you use an (active) environment emitter, you already combine one large with misc. small emitters

i usually keep emitters in external mats or macros, and just disconnect them. imo the fastest and most secure way to turn a light off (and doesn't need to change values also); if i need to hide the emitting object, i just connect a portal (turned off) instead...

you can't lower the power to zero, it's 0.0001 and it continue to emit light
try yourself: dark room with 0.00001 (zero) light emission emitter. Boost the aperture, iso, and....you will get a lot of fireflies.
You have to add a null/no emission emitter node to turn off (physically) the light.