[Sidefx-houdini-list] vops and point clouds

Olex P hoknamahn at gmail.com
Thu Aug 20 16:36:34 EDT 2009


Hey Nicholas,

You could try to create an array of values sampled from all the points in
pciterate loop and sort that array by height (which is in our case a
random(id)). Once you ordered values in array (higher height goes first then
smaller and smaller)  you can go through it and do the same accumulation of
color and alpha. When alpha accumulator reaches 1 you breake a loop.
This should work.

On Thu, Aug 20, 2009 at 3:03 PM, Nicholas Pliatsikas
<nick_p102 at hotmail.com>wrote:

>
> Cheers for the help Olex, yeah looks like stripping out the random height
> stuff works for the additive mode and removes the missing data problem.
>
> Though now it does have the same intersection issue ive been fighting with
> when in a normal mode, so my image bombing still suffers from intersection
> between layers. It seems to intersect at the average center point of each
> circles radius, which makes sense.
>
> Is that what you are meaning by the discs should be sorted? I still cant
> see how to solve that issue :¬/
>
> screengrabs of the lovely intersection.
> http://cid-1a66319ec36b56ba.skydrive.live.com/self.aspx/misc/uv.jpg
>
> http://cid-1a66319ec36b56ba.skydrive.live.com/self.aspx/misc/colour.jpg
>
> Cheers
> Nick
>
> > Date: Thu, 20 Aug 2009 13:52:36 +0100
> > From: hoknamahn at gmail.com
> > To: sidefx-houdini-list at sidefx.com
> > Subject: Re: [Sidefx-houdini-list] vops and point clouds
> >
> > Well it was mistake that order doesn't matter. Discs should be "sorted"
> :)
> > But we did it in previous versions so shouldn't be a problem to add sort
> > again.
> >
> > On Thu, Aug 20, 2009 at 12:56 PM, Olex P <hoknamahn at gmail.com> wrote:
> >
> > > Oops sorry that was a user mistake again. This is what you probably
> want
> > >
> > >
> http://www.hotmail.ru/download.php/?file=:pcdvd3.hip&host=alex-hawk.hotmail.ru/flashcard&user=alex-hawk&lng=ru
> > >
> > >
> > >
> > > On Thu, Aug 20, 2009 at 12:48 PM, Olex P <hoknamahn at gmail.com> wrote:
> > >
> > >> Humm, I made a test but for some reason I see the clipping that you
> have
> > >> on your screenshot. The rest seems to be fine.
> > >> Have to check what exactly causes that clipping.
> > >>
> > >>
> > >> On Thu, Aug 20, 2009 at 12:33 PM, Olex P <hoknamahn at gmail.com> wrote:
> > >>
> > >>> Hi Nicholas,
> > >>>
> > >>> I believe all what you need is just go through all the points in
> radius
> > >>> and sum all the values of alpha on them. The order doesn't really
> matter.
> > >>>
> > >>>
> > >>> On Thu, Aug 20, 2009 at 11:54 AM, Nicholas Pliatsikas <
> > >>> nick_p102 at hotmail.com> wrote:
> > >>>
> > >>>>
> > >>>> Didnt realise the refract limits would affect the point cloud data.
> I
> > >>>> will check into that.
> > >>>>
> > >>>> I had a good think about what was causing the problems last night, I
> > >>>> think its due to how a random ID variable is working in relation to
> the
> > >>>> order in which the point cloud data is being seached.
> > >>>>
> > >>>> For example if the current points random ID value is bigger then the
> > >>>> random ID value of the next point it will be ignored, that point
> will be
> > >>>> ignored. I guess what is really needed is some way of sorting the
> point
> > >>>> datas random ID values then bring those in sequential. But I have a
> feeling
> > >>>> thats not possible at all. So im trying another approach, and
> changing the
> > >>>> order of where the random call is happening, i.e clipping it with
> the alpha
> > >>>> map then running the if statement to check what the highest visible
> layer
> > >>>> is.
> > >>>>
> > >>>> This is much tricker then i first thought..
> > >>>>
> > >>>> Cheers
> > >>>> Nick
> > >>>>
> > >>>> > Date: Wed, 19 Aug 2009 09:40:51 -0700
> > >>>> > From: daveinengland at gmail.com
> > >>>> > To: sidefx-houdini-list at sidefx.com
> > >>>> > Subject: Re: [Sidefx-houdini-list] vops and point clouds
> > >>>> >
> > >>>> > I can't get to the files you referenced because of our firewall,
> but
> > >>>> have
> > >>>> > you checked the refract limit on your objects? If this is too low,
> the
> > >>>> rays
> > >>>> > will be limited by this. Also, there is the opacity limit in the
> ROP
> > >>>> may be
> > >>>> > limiting your rays.
> > >>>> >
> > >>>> > Just a thought.
> > >>>> >
> > >>>> > Dave
> > >>>> >
> > >>>> > On Wed, Aug 19, 2009 at 2:25 AM, Nicholas Pliatsikas
> > >>>> > <nick_p102 at hotmail.com>wrote:
> > >>>> >
> > >>>> > >
> > >>>> > > Hey guys and gals.
> > >>>> > >
> > >>>> > > After doing a good bit of work on the point cloud shader ive hit
> a
> > >>>> problem.
> > >>>> > > To me it seems that there is some optimisations happening with
> the
> > >>>> point
> > >>>> > > cloud data or its just a bug with code/mantra .
> > >>>> > >
> > >>>> > > Basically when layering the point cloud circles it looks as if
> > >>>> mantra is
> > >>>> > > cutting out much of the underlying circles, creating a problem
> when
> > >>>> layering
> > >>>> > > images using alphas. i.e parts of the underlying images are cut
> off.
> > >>>> > >
> > >>>> > > I can't see a problem with the code i added, so I went back to
> the
> > >>>> example
> > >>>> > > Olex sent me and changed it to be additive. This illustrated the
> > >>>> same issue.
> > >>>> > > You can see a screen grab here
> > >>>> > >
> > >>>> > >
> > >>>>
> https://rcpt.yousendit.com/727895459/45f82a647fbe6eae52df9dc836f604f3
> > >>>> > >
> > >>>> > > If it is a bug/limit with mantra I wills end this off to sidefx
> > >>>> support.
> > >>>> > >
> > >>>> > > I have also saved out the additive version of the hipfile, you
> can
> > >>>> download
> > >>>> > > it here.
> > >>>> > >
> > >>>> > >
> > >>>>
> https://rcpt.yousendit.com/727894133/de680b2c71c2c8d61f6dc0700d9d57a4
> > >>>> > >
> > >>>> > > I hope this is something we can get around as it will be a
> really
> > >>>> nice way
> > >>>> > > to add controlled details to scene. Just a note it also seems as
> if
> > >>>> there is
> > >>>> > > the odd point radius that isnt being added correctly either (the
> > >>>> green
> > >>>> > > circles at the bottom right of the screen for example)
> > >>>> > >
> > >>>> > > Cheers
> > >>>> > > Nick
> > >>>> > >
> > >>>> > > > From: nick_p102 at hotmail.com
> > >>>> > > > To: sidefx-houdini-list at sidefx.com
> > >>>> > > > Date: Fri, 14 Aug 2009 15:55:02 +0000
> > >>>> > > > Subject: Re: [Sidefx-houdini-list] vops and point clouds
> > >>>> > > >
> > >>>> > > >
> > >>>> > > > Thanks for that Olex :) thats a great example, I see what you
> > >>>> where
> > >>>> > > meaning in your code about using the maxheight random calls.
> Just
> > >>>> trying
> > >>>> > > this out in vops, having some oddities but will try a few more
> times
> > >>>> until i
> > >>>> > > resort to vex coding ;¬) as i need to quite abit inside that
> loop.
> > >>>> > > >
> > >>>> > > > Cheers mucho!!!
> > >>>> > > > Nick
> > >>>> > > >
> > >>>> > > >
> > >>>> > > >
> > >>>> > > > > Date: Fri, 14 Aug 2009 13:46:49 +0100
> > >>>> > > > > From: hoknamahn at gmail.com
> > >>>> > > > > To: sidefx-houdini-list at sidefx.com
> > >>>> > > > > Subject: Re: [Sidefx-houdini-list] vops and point clouds
> > >>>> > > > >
> > >>>> > > > > Oops, that was toooo quick test. There is correct one
> > >>>> > > > >
> > >>>> > > > >
> > >>>> > >
> > >>>>
> http://www.hotmail.ru/download.php/?file=:pcdvd2.hip&host=alex-hawk.hotmail.ru/flashcard&user=alex-hawk&lng=ru
> > >>>> > > > >
> > >>>> > > > > On Fri, Aug 14, 2009 at 1:33 PM, Olex P <
> hoknamahn at gmail.com>
> > >>>> wrote:
> > >>>> > > > >
> > >>>> > > > > > Hey,
> > >>>> > > > > >
> > >>>> > > > > > There is a quick example
> > >>>> > > > > >
> > >>>> > > > > >
> > >>>> > > > > >
> > >>>> > >
> > >>>>
> http://www.hotmail.ru/download.php/?file=:pcdvd.hip&host=alex-hawk.hotmail.ru/flashcard&user=alex-hawk&lng=ru
> > >>>> > > > > >
> > >>>> > > > > > AA isn't included! :p
> > >>>> > > > > >
> > >>>> > > > > >
> > >>>> > > > > > On Fri, Aug 14, 2009 at 12:24 PM, <eetu at iki.fi> wrote:
> > >>>> > > > > >
> > >>>> > > > > >> >> >> Hey Peoples
> > >>>> > > > > >> >> >>
> > >>>> > > > > >> >> >> Im currently working on an image bombing point
> cloud
> > >>>> shader
> > >>>> > > and hit
> > >>>> > > > > >> a
> > >>>> > > > > >> >> >> problem i dont quite understand how to solve.
> > >>>> > > > > >>
> > >>>> > > > > >> Here's a thread from Georg which might well be relevant
> for
> > >>>> you
> > >>>> > > > > >>
> > >>>> > > > > >>
> > >>>> > > > > >>
> > >>>> > >
> > >>>>
> http://forums.odforce.net/index.php?/topic/6967-a-shader-each-day/page__view__findpost__p__47148
> > >>>> > > > > >>
> > >>>> > > > > >> I vaguely remember another forum thread with someone
> battling
> > >>>> with
> > >>>> > > the
> > >>>> > > > > >> same problem, but can't find it now for the life of me. I
> > >>>> think it
> > >>>> > > was
> > >>>> > > > > >> about overlapping fakeshadow blobs, if you happen to be
> able
> > >>>> to find
> > >>>> > > it :)
> > >>>> > > > > >>
> > >>>> > > > > >> eetu.
> > >>>> > > > > >>
> > >>>> > > > > >>
> > >>>> > > > > >> _______________________________________________
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> > >>>> > > > > >>
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> > >>>> > > > > >>
> > >>>> > > > > >
> > >>>> > > > > >
> > >>>> > > > > _______________________________________________
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