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I need to make a plane shine light only in one direction (or a very narrow angle range) like a spotlamp, or a projector but I don't want to use a spotlamp - I need a wide beam of light, that doesn't spread out in all directions. Spotlamp would produce a tiny cone of light, not a wide beam.

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  • $\begingroup$ area lamp is not a solution for you ? can you give an illustration of what you need ? $\endgroup$ – lemon Jun 16 '16 at 11:06
  • $\begingroup$ Only light type I know in Cycles that emits parallel rays is the sunlight, I think, all others are omnidirectional and emit in all directions. Perhaps some vector math can do the trick, but I am not smart enough to come up with a solution myself. $\endgroup$ – Duarte Farrajota Ramos Jun 16 '16 at 12:38
  • $\begingroup$ See this blender.stackexchange.com/questions/1096/… $\endgroup$ – Duarte Farrajota Ramos Jun 16 '16 at 13:07
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    $\begingroup$ It could be easier to just model some mesh of the desired form which beam of lihgt should have. Then the mesh will be given some emission / transparent / etc. material and probably composited for finer effect. $\endgroup$ – Mr Zak Jun 16 '16 at 15:39
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As you asked for a wide area :

Use an area lamp framed by an open cube (or another shape).

The lamp material is constrained by a constant falloff so that you have sharp borders on the light projection.

enter image description here

The open cube, is hidden on the rendering and diffuses nothing, due to this setting in its object properties :

enter image description here

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Ok, I've figured out a way to do this the way I wanted. I hope to make a tutorial about this soon.

Node setup for the material

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    $\begingroup$ given that the promised tutorial never materialized, it is hard to understand the reasoning behind the proposed answer. $\endgroup$ – cegaton Apr 12 '17 at 4:21
  • $\begingroup$ It is actually pretty simple, if it facing away, it simply emits black light. $\endgroup$ – Cem Kalyoncu Apr 8 '18 at 5:21

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