IES lights emission scale. SkIndigo

[torsten]

Does Indigo take into account emission scale (power) and efficacy for IES lights?

I have some problems with the lighting. I want to create a light source with a certain IES. So far so good, I marked the IES button and chose the IES file which has all necessary information in it. But it seems to have some problems with the power value. It turns gray, when I check the IES button which would be ok, because I have the candela values for each angle. Still it seems to use the values of power and efficacy. If I have these values identical in two different emitter materials, I get the same amount of light on a plane surface, even if I change the candela values. The distribution is fine, just the values are wrong. If I change the power efficacy values and then check the IES button, I get different values with the chosen distribution. I think this has to be a bug. How does it exactly work?


Torsten

[Pibuz]

I think the powers are actually disabled with IES light because embedded in the IES file itself. I usually split the different IES light in different layers, so I can adjust their specific values during the rendering.

I don't know if I answered your question..

[Headroom]

An IES file is basically the measurement of the light intensity distribution stored in ASCII format, thus all the settings in Indigo associated with the power output of a light source are disabled. You can define the color though, e.g the blackbody temperature.

As Pibuz suggested a commonly used practice is to assign the IES lights and the other light sources in your scene to different light layers and adjust the light layers. Depending on the difference in light output of the light sources in your scene, however, the layers with the darker sources will be assigned less render time by Indigo and as a result take longer to clear up. So be prepared for longer render times.

For a final render you can then adjust the non IES lamps according to your light layer settings and place all the light sources on one (or fewer) layers. I have not tried this last step with conjunction with sun light or with HDR lighting and I am not sure if it works in these cases.

[torsten]

thanks for your answers, but the way it is supposed to be doesn't seem to be the way it is. If I use different candela values in my IES file (I only have one value for the 0° angle) it doesn't change the intensity. It keeps to be the same intensity on each spot of lighting. If I change the power setting, the spot stays the same, but has a different intensity. What do I do wrong?

Torsten

P.S. I use SketchUp and SkIndigo

[Headroom]

You may be doing this already, however, for these experiments you may want to switch from reinhard tone mapping to linear tone mapping.

This is unlikely to fix the actual problem but comparing intensities and distribution patterns is much easier this way.

Also if in doubt what effect the buttons in Sketchup have, you can always check the IGS file (Indigo Scene File) that Sketchup hands over to Indigo. That will provide you with direct feedback whether a button that you have activated has any effect.

[Headroom]

I tinkered around in Blender/Blendigo 2.4.13 a little.
I used IES files that I had loaded down a while ago from the Solux website and modified these a little.

I used two IES files directly side-by-side. One as a control, the other one I modified either the file itself, or Blendigo settings.

- Multiplying all candela values by 10 did not change anything.
- Changing only some of them - as expected - changed the pattern. I bumped up a few of them by factor 10 and let most at the initial value. The bumped up values got brighter but the unchanged valued got darker.
- bumping up gain also changed that value in the IGS file (not IES file ) but the resulting image did not change.
- Increasing the Emission Value in Blendigo changed the overall lamp intensity

Soo.......my conclusion based on these rather limited experiments is that:

Indigo normalises the candela values in the IES file to values between 0 and 1 and then uses the Emission Value for the overall lamp output.

I have no Idea if that is actually what happens so some developer feedback would be appreciated

According to this article http://www.kxcad.net/autodesk/3ds_max/A ... ormat.html the IES file contains the initial rated lumens for the lamp and an overall multiplier for all the candela values. I would believe that Indigo makes no use of these values.

[torsten]

thanks headroom,

made the same experiences.

[torsten]

<mesh_name>Emitter2</mesh_name>
<emission_scale>
<material_name>Emitter2</material_name>
<measure>luminous_flux</measure>
<value>110200.0</value>
</emission_scale>
<ies_profile>
<material_name>Emitter2</material_name>
<path>TX_default/Diodenlaser2.ies</path>
</ies_profile>

There is a value for the luminous_flux (taken out of SkIndigo) + the IES file.