sounds cool, eh, the title :)

ok, so as u can imagine from the name of post this one gona be mesy crazy and ununderstandable. well i kind of got this idea while semi sleaping, so what kind of clearity can u expect from such a state of mind?

anyways. i was always interested in wind, as an effect in 3d, or cg. Now we all know this 2d effect in photoshop, not sure it might be actualy named wind. well its similar to directional blur. it shifts, pushes pixels, only some pixels i guess, to the directio of wind. yes, just had a look its nder stilize effects in photoshop.

anyways, so i was thinking could we do somthing similar in 3d? to alow wind actualy to push pixels?

and here is what i come up whith.

1. the wind in 3d software is usualy just a direction and strenght, i meaqn it has such parameters. well i am not to familiar whith it, so corret me if i am wrong.

(look at the picture “A”).

So if we would have just strenght and direction, then our wind would be simple photoshop efect, and no nead to bather thinking how to implement it.

therefore we would nead the whind in a scene to be somehow distributed in more interesting fasion. now here are some thoughts. 1. we are all familier whith whind icon, the one which see as an object in our scene, the one we rotate to change direction of winnd, the one we animate.

well, even icon has its position in 3d space, so we can have then distance from pixel we are curiently rendering to wind icon in scene. acording to this distance we can decide upon strenght. meaning, closer pixel (i shuld say peace of geometry which is “seen” from a pixel in viewing plane) is to wind source, or icon, stronger the effect will be.

now another thing is, sometimes when u hide behind something wind doesnt blow as strong. how can we do that?

why not to employ our raytracing engine? if we would think that wind icon is a light source, we could render a shadow. (using secondary ray, which is pointed towards light source, in this case towards wind picture “B”) so we would have a shadow of a wind in a way.

and we shuld not apply this wind effect on a pixels which are under wind shadow.

now a nex step would be, ….

ok there is no sharp distinction where the wind “is” and “is not ” in real life, we have all gray areas in betwean.

how do we do that in our raytraced wind shadow?

why dont we drow some vectors, to see how strong pixels would be affected (lenght of vector) and direction. so lets have a look at picture “c” (well part of the picture which is labeled “c”)

raytracing wind

and now in a right side of picture we have thuse black numbers 1-4.

lets imagine 1 and 2 are pixels which shuld be affected by our crazy wind effect.

while 3 and 4 are pixels in a wind shadow, so we will not apply any effects on them. but we whant to get rid of sharp edge…

why dont we make pixels in shadow have some sort of influence radius. lets look at red circles around pixels 3 and 4.

we see that pixel’s nr. 3 circle touches pixel nr 1. so what we will do is we ll draw a vector from pixel who has whind effect, this would be pixel nr1 towards pixel in a wind shadow, nr.3. normaly that would be a straight line, but we will take in to acount wind direction and draw somethig like in right top corner of our ilustration. the black curved arow. now acording to thuse wectors we will finaly apply pixel shifting looking at our vectors which will guide the directions.

i know its all crazy, but why not. might be somthing interesting could be done thinking about what i wrote,

i know i wqas not wery clear when i talk about 2d pixel as a end value in rendered picture, when its pixel in viewing plane, when its a point in 3d space, which is being seen from viewing plane and so on.

but no nead to be all critical here, its only food for thoughts, not something to write a phd on :)

what u think?

again, any voluntears to write a renderer?

you can also wisit my portfolio.
dont like english? u can (try) readig it in lithuanian or anny other language here! alternative, has no lithuanian :(
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4 thoughts on “raytracing the wind, and wind shadows.

  1. Its an interesting concept, that gets me wondering about all sorts of other potential uses of a ‘pseudo ray trace’ system…
    Always interesting reading your crazy 3d ideas!! :)

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