I started to study blender because I want to perform some simulations on bicycle lighting.

My goal is to take a picture of a beam pattern against a wall, then use it as the Bidirectional EMISSION Distribution Function for the light source, rendering its illumination pattern when actually used along a road or other outdoor environment.

For example, a typical distribution for a vehicular headlight is as follows:

enter image description here

Then, I would create a light source with this custom emission pattern (sort of an "UV map" for luminous emission intensity) to render images such as these, with a fair amount of realism (I don't plan to get state-of-the art, 100% physically accurate simulation):

enter image description here

So my questions are:

  • Is it possible to do shuch a thing in Blender?

  • If it is, which concepts should I look for?

I plan to use Cycles rendering engine.

  • 1
    $\begingroup$ You might be interested in this $\endgroup$
    – gandalf3
    Nov 1, 2013 at 20:00
  • $\begingroup$ @gandalf3 that is very interesting, but I think I still have a lot to learn before making it work... Thank you for now, I'll surely take a deeper look as soon as I can! $\endgroup$ Nov 2, 2013 at 0:25

1 Answer 1


Spot into textured transparent shader will work. like this

enter image description here


enter image description here

  • $\begingroup$ That's interesting... Since I won't model the headlamp reflector anyway, I think anything that gives the radiation distribution is fine. Although there is a suggestion to use actual .IES files (which I don't have anyway), the possibility to use plain old PNG is yet more attractive. Gonna try it this weekend, thanks!! $\endgroup$ Nov 2, 2013 at 0:12
  • $\begingroup$ I have studied what I could in the weekend, and came to the point where I have the textured road, the cameras and the light source (I am using spotlight). But the images you posted ended up a bit too small, so I would like to ask what I should do from now, to make a scene like yours? Which concepts/panels/properties should I use? What is a "shader" supposed to be and how do I create one like yours? $\endgroup$ Nov 5, 2013 at 15:20
  • $\begingroup$ Apply your texture to the plane, select use nodes in node editor window. Select transparent shader. pipe texture as in the picture I posted. You can scale the plane in which you applied your image to adjust the size of the projection. $\endgroup$ Nov 6, 2013 at 21:29
  • $\begingroup$ Ok, after a lot of tinkering I figured it out and gonna put some feedback as soon as I have a good-looking result. One last question: I noticed this works in Cycles, but not in Blender Render. Do you know if this is possible in Blender Render, or something similar to it? $\endgroup$ Nov 7, 2013 at 15:59

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