Angular power distribution of a Spot Lamp

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Angular power distribution of a Spot Lamp

Postby igall » Wed Feb 28, 2018 8:36 am

Hi,
Could anyone please describe the angular power distribution of a LuxRender Spot Lamp?
Can the angular power distribution be controlled through Blender?
If the answer is yes, then how?
Many thanks in advance,
Igal

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Re: Angular power distribution of a Spot Lamp

Postby igall » Sun Mar 04, 2018 1:49 am

I’m posting again to try focusing the question in hope that anyone can solve the puzzle.
The angular distribution of a spot lamp is described as constant, and fading at some angle - at http://www.luxrender.net/wiki/LuxCore_SDL, Type: spot (field scene.lights.<light name>.conedeltaangle)
On the other hand, I did an experiment capturing a flat wall perpendicular to the camera - and as a result I have obtained curly angular power distribution. It is displayed on the image below.
Can anyone tell how can I configure the angular power distribution to be constant?
Otherwise, can anyone refer to an alternative source describing the spot lamp angular distribution?
Or point out what I did wrong?
Many thanks in advance,
Igal
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Re: Angular power distribution of a Spot Lamp

Postby Dade » Sun Mar 04, 2018 8:31 am

The distance from the light source when using a wall is not constant. You have to use a sphere to a correct result.

Spot lights have a constant distribution if you are not using the fall off parameter.
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Re: Angular power distribution of a Spot Lamp

Postby Dade » Sun Mar 04, 2018 8:36 am

Btw, you can use a point light with a IES profile if you want an arbitrary distribution.

P.s. and the new software used for the project reboot and described in the news section.
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Re: Angular power distribution of a Spot Lamp

Postby ipap » Sun Mar 04, 2018 9:52 am

Dade wrote:Spot lights have a constant distribution if you are not using the fall off parameter.


Is it possible to know what is the value of this parameter in Blender?

Thanks
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Re: Angular power distribution of a Spot Lamp

Postby B.Y.O.B. » Sun Mar 04, 2018 10:52 am

Set the "spot blend" parameter to 0.
However from your screenshot it looks like you use the projector lamp which does not have this parameter (it is always constant, only controlled by the projected image).
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Re: Angular power distribution of a Spot Lamp

Postby igall » Mon Mar 05, 2018 11:09 am

Many thanks for clarifying this issue.
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