[req] volumetrics/ dust and laser emiters

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oodmb
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[req] volumetrics/ dust and laser emiters

Post by oodmb » Wed Nov 15, 2006 4:25 pm

the ability to create a "laser" like mesh emitter. this mesh emitter doesn't have to act like a real laser, just emit all rays or photons or whatever without a random factor at the direct angle of the face's normal. the photons would also be of a single color without random factor.

this might not sound very useful, but would come in handy for testing materials, as materials get more complex and sss is implemented, it could also be used for testing where the light is bouncing in the scene without doing a whole render. but i bet people will find a way to use this artisticaly.

along with my mesh laser, i would also like to request a code that allows for "volumetrics" rather than just having a specific light applied volumetrics, this would be possible by making a general random factor for the scene (very low factor) which would allow the rays or photons to bounce at a random angle without having hit an object in such a way that it would mimic particles in the environment. this ability as to make rendering times faster would ideally also be scaled to the power of the lights in the scene, so that if there is a dark scene with one light emitting a "beam" which is vastly brighter than the rest of the scene, the light would also need less of a random factor and thus indigo would scale that automaticaly. the random factor should also be able to be scaled within the xml and infile. another way (probably harder to program but easier on the cpu) would be to instead of make the whole scene have the random bounce factor, just one emitter.

such a thing would allow the visiblity of say, a ray of sunlight coming from the window of a church or allow the visibility of the laser beam.

lego
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Post by lego » Wed Nov 15, 2006 9:52 pm

you can build your own laser :)
just create a box with an emitter (colored too) inside, and create a small hole
the hole has to have a long... "neck". I'll post a drawing if it's not clear enough :P

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zsouthboy
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Post by zsouthboy » Thu Nov 16, 2006 2:56 am

Yeah, you can already build a laser, just like we have to in real life :)

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oodmb
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ehh, no cant

Post by oodmb » Thu Nov 16, 2006 3:14 am

1. in real life, building a laser requires the use of a crystal which CONVERTS (not absorbs all but one color) the energy inserted from light into coherent light. this involves the individual electrons being excited in the material by the light and jumping to a higher energy state then all the electrons jumping back down at the same time and releasing the coherent light.
2. coherent light is not just very small light, it involves multiple rays all in the same direction without diffusion. putting a light in a box with a whole would not cause all the rays emitted to be in the same direction, rather it would cause the light to diffuse like a lense or pinhole camera. it would also not allow the light to be emmited in one color. however, if you made it small enough so that it would let only one ray through it would negate the use of a laser to study the diffusion of light throught a scene, or even use in testing materials

lego
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Post by lego » Thu Nov 16, 2006 3:52 am

to have light emitted in one color, simply use a colored emitter

to fake a laser I used this scheme. it's not a real laser, but it's not so bad
Image

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oodmb
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no

Post by oodmb » Thu Nov 16, 2006 5:11 am

i have used that technique within yafray before and ended up unhappy with its results. as i said before, it acts like a pinhole camera although with the stem it narrows the result down to a couple of rays. the dispersion of light is still too high. a teqhnique which works better, still not a laser, is to use a parrabolic mirror and a spherical light with the half not facing the mirror covered by an opaque mesh, this might cause a spot in the middle of the light but in the mean time it is a substitute. to make it easier, a conical light could be used along with a conical mirror. however, the easiest way would be to program a couple of lines in indigo which would allow light to be emmited all in the same direction of the face's normal

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zsouthboy
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Post by zsouthboy » Thu Nov 16, 2006 6:36 am

Lasers are hardly a perfect source of parallel photons.

I suspect you haven't actually TRIED faking it in indigo. You do get good results.

Oh, and quite possibly (thinking through this in my head), it's not as easy as a few lines of code: due to using a random walking algorithm to detect rays, it's possible that the exact vector of those exactly parallel photons could never be discovered.

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