[Sidefx-houdini-list] vops and point clouds

Nicholas Pliatsikas nick_p102 at hotmail.com
Fri Aug 21 05:55:18 EDT 2009


I didnt even think of using arrays to sort the problem Simple:¬D This is the sort of thing I do all the time in python etc I completely forgot Vex has array support now, as you dont get access to them through vops which is what I normally use for shaders. I will give this a go.
Cheers
Nick

> Date: Thu, 20 Aug 2009 21:36:34 +0100
> From: hoknamahn at gmail.com
> To: sidefx-houdini-list at sidefx.com
> Subject: Re: [Sidefx-houdini-list] vops and point clouds
> 
> 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.
> > > >>>> > > > > >>
> > > >>>> > > > > >>
> > > >>>> > > > > >> _______________________________________________
> > > >>>> > > > > >> Sidefx-houdini-list mailing list
> > > >>>> > > > > >> Sidefx-houdini-list at sidefx.com
> > > >>>> > > > > >>
> > > >>>> https://lists.sidefx.com:443/mailman/listinfo/sidefx-houdini-list
> > > >>>> > > > > >>
> > > >>>> > > > > >
> > > >>>> > > > > >
> > > >>>> > > > > _______________________________________________
> > > >>>> > > > > Sidefx-houdini-list mailing list
> > > >>>> > > > > Sidefx-houdini-list at sidefx.com
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