OctaneRender® 1.024 beta 2.45 (lin/mac/win) [OBSOLETE]

[radiance]

Hi guys,

I will try to explain the new light params with a very simple analogy, so anyone will understand it correctly:

Before we had one parameter called 'power'.
This meant, that the area light emits light with intensity 'power'.
If you make your object which is the area light larger, and you end up having 2x the surface area, you will have 2x as much energy (eg light) radiating into your scene from it.
Eg, imagine you have a tennisball and you wrap it in a glow-in-the-dark plastic sheet material, and you illuminate a dark room by it.
Next, You take a basketball and you wrap it in the same glowing plastic material. You would need probably 10x as much glow plastic sheet material to cover the basketball versus the tennisball.
If you use the basketball instead of the tennisball, you will end up having more surface area glowing, so you will illuminate your room with more light.
This was the system we have before. Eg power = lumen over area.

With the new physical parameters, we now have 'watt' and 'efficiency'.
Think of watt as the amount of electricity you would send to the emitter.

Eg we take our tennisball again, and wrap it in some hypothetical sheet material, that emits light when you connect it via a cable to a power source.
Eg it converts the electricity into light.
In this case, if we take the tennisball, and feed it 10 watts of electricity, we end up with a glowing tennisball illuminating the room.
Now imagine that we send the exact same 10 watts of electricity in the basketball.
Since we're distributing these 10 watts of electricity over a much larger area, the glow intensity will be much less.
If we want to have the same effect as before, we need to send more watts to it to ge the same intensity.

Imagine you had a tungsten incandescent glow-lamp, normal size, and you had a second one that is 10 meter tall, really huge.
The 10 meter tall one has a tungsten wire of 2-3 meters long, 5cm thick and weighs 7 kilos.
If you send 100 watts into the large lamp, it will glow very faintly, whereas 100 watts on the normal sized lamp will make it shine really bright.
You wound need several thousands of watts to make the large lamp shine as bright.

On the other hand, if you place the small lamp with 100watts of power in a large theatre hall, the hall will be dark,
and if you place the large lamp in it with say 5000 watts, the whole theatre hall will be illuminated.


The remaining parameter 'efficiency' is simply an additional scale for practical reasons.
Eg, imagine you want to add a lightbulb to an interior, just look up the efficiency for an incandescent lamp on wikipedia, and use that along with the desired watts and you are done.
You can find many efficiency ratings for different kinds of lamps around the web.

Also, as efficiency is a texture and is between 0.0 and 1.0, it doubles as a texture channel, to modulate the area light.


The firefly issue is probably due to people having a large and small arealights in scenes, and with the new parameters the output is completely wrong, with far too high power on the small area-lights, creating more noise. (this will converge given more time, it's simply undersampled light contributions, they are not bugs)

I think it's best to take your scene, remove all configurations for the lights, and redo them all, using the watt/efficiency workflow.
Eg, 100 watt bulb in the ceiling, 25 watt in a small table/desk lamp, and 0.01 watt for LEDs etc...

That's it, hope this makes it clear to those who did not understand it fully,

Radiance

[radiance]

On a side note, an important thing to take into account is that other unbiased engines like maxwell, fry, indigo etc,
have a tonemapper that automatically adjusts it's intensity.

As such, the final tonemap will use the average intensity of the film, so the scale of scenes won't impact the overall brightness with physical controls on area lights,
as the tonemapper automatically adapts.

In octane, there is no automatic adaption, you manually use the exposure slider to do so.

It's very easy to have completely incorrect intensities for lights with automatic adaption in the tonemapper,
eg a simple scene with one area light lightbulb, will look identical with 10 watt or 10.000.000 watt as the tonemapper adapts/normalizes it.

Therefore it's important to obey correct scale and use correct intensities, eg driving the power of a lightbulb up to a million watts to make your scene look normally illuminated will hint to the fact that you are importing in the wrong scale and you're interior is kilometers large.

The best workflow is:

* Make sure you work in correct scene scale
* Configure you're lightsources with correct watt/efficiency, eg 15, 25, 40, 50, 60, 80, 100 watt lightbulbs.
* Use the exposure of the tonemapper to adjust you're render's total illumination level


Radiance

[dave62]

i found some tools for win http://www.photometricviewer.com/1_4_Download.html to view ies and create ies tex. if anybody knows some more tools/sources especially for linux, please share:)

[roeland]

btw..there must be some converters out there to convert real ies files to image tex??

You can load the IES file directly into Octane. You need to use a floatimage node, and then you can load an IES file instead of an image.

[grimm]

Thanks Radiance,

In that case then the power slider tops out much, much too soon and needs to be expanded significantly. Right now it only goes up to 100 watts if I read your post correctly? I'm still a little confused as there does not appear to be any correlation between watts and the amount of light emitted from an emitter. It all depends on the materials the emitter is made from and it can vary significantly. A 100 watt halogen bulb is much brighter then a 100 watt incandescent bulb, which is different from an LED, etc. If I wanted to simulate the sun I would need to be able to set the power to trillions of watts (or maybe more?) for it to work right.

[face]

Use an other import scaling so that the emitted meshes are bigger.

Edit:
If the mesh is bigger in its measurement, then it produce more emissions and the ilumination is brighter

This has changed in beta 2.45, the power settings now control the total amount of illumination coming from an emitter, independent from its size. To get a brighter image you can export the scene in a smaller size.

Thats not what i mean.
With mesh i mean the imported obj-file, also the whole scene.
Say the scene have 8x8meters and i export in meters, the scene is darker as i export the scene in decameters.
Thats the ex/import scaling.

face

[dave62]

btw..there must be some converters out there to convert real ies files to image tex??

You can load the IES file directly into Octane. You need to use a floatimage node, and then you can load an IES file instead of an image.

YAY great! ..could it be that it was all so simple...

[face]

Use an other import scaling so that the emitted meshes are bigger.

Edit:
If the mesh is bigger in its measurement, then it produce more emissions and the ilumination is brighter

face

I guess where I getting confused is that it shouldn't matter how big the emitter is, and according to Marcus and Roeland emitter strength is no longer tied to mesh size. I should be able to make a ball the size of the sun, and make it emit as bright as the sun or brighter. Or make a 1cm size cube and have it as bright as the sun too.

Thats what i mean...

face

[radiance]

Thanks Radiance,

In that case then the power slider tops out much, much too soon and needs to be expanded significantly. Right now it only goes up to 100 watts if I read your post correctly? I'm still a little confused as there does not appear to be any correlation between watts and the amount of light emitted from an emitter. It all depends on the materials the emitter is made from and it can vary significantly. A 100 watt halogen bulb is much brighter then a 100 watt incandescent bulb, which is different from an LED, etc. If I wanted to simulate the sun I would need to be able to set the power to trillions of watts (or maybe more?) for it to work right.

Yes, incandescent, LED, fluorescent, does'nt matter, as you use the efficiency to compensate for the type of lamp.
Regarding max 100, i thought the default was higher than 100 watts, i've asked roeland to increase it in the mini-update for monday to say 100.000.

Due to a few assumptions in the engine, going higher than 100.000 watt is not a good idea, so making a sun is not possible for now.
maybe in the near future we will add a sun+HDR system for this purpose.
You don't need a trillion watts, if you make you're sun sphere smaller and closer to your scene.
Nevertheless, i would'nt model suns as area lights, they will never be %100 correct.
sunsky was made for that purpose.

Radiance

[suhail_spa]

That's it, hope this makes it clear to those who did not understand it fully,

Radiance

Thanks a ton Radiance...


I am still experimenting with 2.45....
it all runs good..
the new customizable interface is great-
and IES support is really good..and so practical & easy to use.
on target..

now understood it fully after reading your post above..
thanks for the explanation..
no problems so far here...