OTOY Forums

Hi Guys,

Would anyone happen to know how the power node equates to wattage for ies lights?

I just need to get the lighting as accurate as possible.

For example if Light A = 50 watts, should I set the Power Node to 50?



Cheers,
K

I havnt really used these lights but I think I remember seeing a line or two in the manual (not sure if it was Rhino or standalone) about the settings and how they relate to real world light power.

Cheers

Tim

An IES file will define the dimensions of the light. Assuming you create an emitter polygon which matches the light size in the IES file, then the Octane emitter power will be:

lightRadiance * (1 / (lightWidthInMeters * lightHeightInMeters))

I don't think Rhino supports IES lights - so you would need to use IES Viewer to get the light dimensions.

Paul

Hi Paul,
I'm testing IES files.
I've created a simple room with a single sphere to use as a polygon to use as an emitter.
All the data are in the project file.
If I change the scale of the sphere the distribution remains the same. So using an Ies file the distribution is not dependent by the size but only by the shape?
Other question: if I rotate the sphere the x-axis is right but the Y and Z are inverted to me.
Where is the radiance data in the image I link and what are 2x157=314 W in the IES viewer image?
Thanks,
Roy

Hi Roy

I suggest using a single polygon plane rather than a sphere as an IES light source. Use a Spherical Projection, and set the Position Type to Normal Space on the Image node being used for the IES distribution. The Image texture's Projection nodes adjust the light's orientation and direction.

I hope that helps.

Paul

Hi Paul,
I've done your steps.
I can't set the Rotation/Direction of the light.
I don't understand too how is work the relationship between the shape of the polygon and the light distribution.
I send you the new file,
Roy

I've found many differences from the last plugin version and the manual about the IES setting.

I can't set the Rotation/Direction of the light.

I was able to rotate the light in the scene you provided by using the "Octane Material (2)"->Distribution->Projection [Spherical]->Sphere Transformation->Rotation X and Y sliders.

I don't understand too how is work the relationship between the shape of the polygon and the light distribution.

My understanding is that the sphere of the mesh/polygon the IES material is attached to make no difference. It is simply a placeholder for the IES light.

Paul

Hi Paul,

rotating around y nothing happens here, rotating around x and z, yes, but I can't understand in what way it rotates because of the light disappearing soon. Anyway, this is no more a problem for me because I use IES coordinates space and I rotate the polygon to rotate the direction and it works.

About the shape of the polygon, I've understood what's happening. The dimension of the shape seems have not influenced, the shape itself yes. I mean, one plane 1m x 1 m it seems to have the same result of one plane in the same position of 1 cm x 1 cm. But if I use a plane 10 cm x 10 m it changes totally. So it's enough to use a square plane and it works again.
I send you 3 images with these results.

My first issue remains the result of the rendering. I've tested one real lamp from ERCO with Dialux software and set the same lamp in octane. I don't know if I did some mistake but the result is right about the light distribution (using IES and a square polygon) but the final result is very dark and not similar to the Dialux result. I send you two images for this.

Thanks,
Roy

Hi Roy

This is getting to the limits of the knowledge on IES lights - so I suggest posting these questions to the general Octane forum.

Thanks

Paul