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Is there an easy way to cover everything in your scene with a thin layer of
dust. oh and also without taking up huge amounts of memory and slowing the
render speed down too much- ive been thinkink of trying a mesh with a
single triangle to take advantage of mesh instantiation(sp?) but is this
the best answer?
Thanks
Peter
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"Vladimir" <nomail@nomail> wrote in message
news:web.412f9cde347225dd302903ba0@news.povray.org...
> Is there an easy way to cover everything in your scene with a thin layer
of
> dust. oh and also without taking up huge amounts of memory and slowing the
> render speed down too much- ive been thinkink of trying a mesh with a
> single triangle to take advantage of mesh instantiation(sp?) but is this
> the best answer?
> Thanks
> Peter
>
>
i can't suggest any concrete sollutions, but i'll post a few links. first to
a paper i've been meaning to read about metallic patinas, which can look
sort of like dust, in that it's very thin, and "changes" the finish of the
object it is on.
http://graphics.csail.mit.edu/~dorsey/papers/patina/
one question i have is this, where is your dust? airborne? resting on
objects, if so, does it need a thickness to it?
also, another paper i have read, and have been spinning my wheels on when i
have spare cycles up there is this, which deals with covering everything in
your scene with snow. a dust particle and a snowflake might have some
similar properties, such as how it can manage to get slightly under things
even if the path is blocked from straight above. the problem with the
analogy is that dust rarely is built up to a significant thickness like
snow. so maybe dust-as-snow isn't a reasonable match. still an interesting
read.
website:
http://www.cs.ubc.ca/nest/imager/contributions/fearing/snow/snow.html
paper in pdf:
http://graphics.stanford.edu/courses/cs448-01-spring/papers/fearing.pdf
for fun i just searched "computer modeling and rendering of dust" and came
across a paper that cites the above snow paper and patina paper. so maybe
i'm not too far off. that paper can be found here:
http://www.cse.cuhk.edu.hk/~ttwong/papers/dust/dust.html
off to read it now... i've not yet been able to translate any of these or
other things like them into povray use (most of it is over my head though i
intend to try someday), but i'd be curious if anyone has.
good luck, maybe someone will offer real help :)
ross
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"Ross" <rli### [at] everestkc net> wrote in message
news:412faa63$1@news.povray.org...
> for fun i just searched "computer modeling and rendering of dust" and came
> across a paper that cites the above snow paper and patina paper. so maybe
> i'm not too far off. that paper can be found here:
> http://www.cse.cuhk.edu.hk/~ttwong/papers/dust/dust.html
>
the ACM page i found the paper on lists it as related, the paper itself
doesn't cite it. just wanted to clear that up.
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the dust I would be moddelling would be on the upper surfaces of objects -
airborne dust can be pretty well simulated with media. The one thought I
had would be this: Is there any way to create a loop that distinguishes all
surfaces facing in a single direction or at least partly in a direction ie
set to pick up y facing surfaces would also pick up the line x*y. Dont know
whether that makes sense. It would then add a semi transparent layer on top
of the current texture. Im not sure how I would go about writing this or
even if it is possible in povray.
Peter
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"Vladimir" <nomail@nomail> schreef in bericht
news:web.4131e9a1dab9b99e4e987f070@news.povray.org...
> the dust I would be moddelling would be on the upper surfaces of objects -
> airborne dust can be pretty well simulated with media. The one thought I
> had would be this: Is there any way to create a loop that distinguishes
all
> surfaces facing in a single direction or at least partly in a direction ie
> set to pick up y facing surfaces would also pick up the line x*y. Dont
know
> whether that makes sense. It would then add a semi transparent layer on
top
> of the current texture. Im not sure how I would go about writing this or
> even if it is possible in povray.
A few things I noticed while examining dust in my room (don't ask :))
1. (this one is quite logical, and actually more or less what you describe
here) Dust falls down, so parts of your scene that are not accessible from
above (if you know what I mean) will be more or less clean. This can be
accomplished with the projection pattern in MegaPOV, with a blur to make it
more realistic
2. Dust is more visible from low angles than from high angles, this can be
simulated with the AOI pattern, also in MegaPOV.
I combined both to get this result: http://sad.nostalg1c.org/dusttest.png
cu!
--
ZK AKA Gaeriel
http://www.povplace.be.tf
"I don't take money, only girly giggles."
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I have no Idea how this would be done without using lots of tiny particles,
and even then Icouldn't give you much of an Idea of how to write such a macro.
Maybe you should try Megapov's Mechsim function, it might give you the desired
effect. you could write a recursive distribution macro. something that would
randomly distribute the particles throughout a given area (translate <randx,
vector_supplied_by_mechsim+particle_radius, randz>).
I don't know, maybe this is totally crazy, I haven't worked much with
MegaPov. But the only other thing I can think of is writing your own gravity
sim to make the distributed particles fall until the trace macro detects a
surface.
A.D.B.
Vladimir wrote:
> the dust I would be moddelling would be on the upper surfaces of objects -
> airborne dust can be pretty well simulated with media. The one thought I
> had would be this: Is there any way to create a loop that distinguishes all
> surfaces facing in a single direction or at least partly in a direction ie
> set to pick up y facing surfaces would also pick up the line x*y. Dont know
> whether that makes sense. It would then add a semi transparent layer on top
> of the current texture. Im not sure how I would go about writing this or
> even if it is possible in povray.
> Peter
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Vladimir, I think you need to use the "slope y" pattern on a texture
map, with a very grainy texture for the horizontal parts and transparent
for the rest, like I did for my beach scene:
http://www.ignorancia.org/images/personal/coinchas-8b.jpg
I never tried to use this trick for a layer of dust, but I think it can
be very difficult to adjust (dust particles are much smaller than sand
grains).
--
Jaime
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"Zeger Knaepen" <zeg### [at] studentkuleuvenacbe> wrote in message
news:41320edc@news.povray.org...
> "Vladimir" <nomail@nomail> schreef in bericht
> news:web.4131e9a1dab9b99e4e987f070@news.povray.org...
> > the dust I would be moddelling would be on the upper surfaces of
objects -
> > airborne dust can be pretty well simulated with media. The one thought I
> > had would be this: Is there any way to create a loop that distinguishes
> all
> > surfaces facing in a single direction or at least partly in a direction
ie
> > set to pick up y facing surfaces would also pick up the line x*y. Dont
> know
> > whether that makes sense. It would then add a semi transparent layer on
> top
> > of the current texture. Im not sure how I would go about writing this or
> > even if it is possible in povray.
>
> A few things I noticed while examining dust in my room (don't ask :))
>
> 1. (this one is quite logical, and actually more or less what you describe
> here) Dust falls down, so parts of your scene that are not accessible from
> above (if you know what I mean) will be more or less clean. This can be
> accomplished with the projection pattern in MegaPOV, with a blur to make
it
> more realistic
It does fall down, but it also is blown in. In my last apartment which I
just moved out of, it had 3 windows, all facing the street, a main
neighborhood street. I only ever opened one of those windows, and I hardly
ever dusted (ah... my mother would kill me ;)
you could see that surfaces that faced that window had significantly more
dust on them than surfaces that faced away from that window, even near
vertical faces like the side of my television.
nice example image, nonetheless. pretty dusty :)
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I will have to try the slope y texture- that sounds like it could produce
some decent results. Un fortunately I am working in povray and have not got
megapov( I am on dial up and I really dont want to spend hours downloading
it) so most of the other functions suggested are out.
Thanks
Peter
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hi
Zeger : could I maybe get the source code for that example you did. I have
finally turned to the dark side and got megapov and would quite like to
see how you did that.
Thanks
Peter
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