question about subtractive texturing


    Jun 01 2007 | 4:34 am
    Not sure if the title is an official term but at 12am I honestly could not
    think of a better way to express this.
    While this is doable in some (most?) 3d modeling programs, I am not sure if
    this is doable in jitter. Namely, I am hoping to have 3d objects floating in
    space and when they move into the area where a [preferably invisible]
    texture is being projected (a texture of a quicktime movie for instance),
    their body will reflect a particular part of this otherwise invisible
    texture. So, in other words, if a 3d object finds its way into the top-right
    corner of the projected texture (which would be invisible otherwise), then
    their body would reflect that top-right corner, in effect becoming
    doubly-textured object.
    This would in effect seem as if the invisible texture in question is being
    subtracted against the shapes of 3d objects, allowing only to see parts of
    the texture where 3d objects reside. Hence, my [awkward?] title :-).
    Any help in this matter is most appreciated!
    Ivica Ico Bukvic, D.M.A.
    Composition, Music Technology, CCTAD, CHCI
    Virginia Tech
    Dept. of Music - 0240
    Blacksburg, VA 24061
    (540) 231-1137
    (540) 231-5034 (fax)
    ico@vt.edu
    http://www.music.vt.edu/people/faculty/bukvic/

    • Jun 01 2007 | 4:42 am
      Did you see my sharing is fun projective texture patch from last
      night? This could serve your purpose if you want the projected
      texture to be arbitrarily located in the scene. You'd have to change
      things a little of course to get multitexturing, but it could easily
      be done. The other option which is less flexible but easier on the
      GPU and more straightforward to understand is to use object space
      texture coordinates with a border color of black and a @wrap
      clampborder.
      wes
      On 5/31/07, Ivica Ico Bukvic wrote:
      > Not sure if the title is an official term but at 12am I honestly could not
      > think of a better way to express this.
      >
      > While this is doable in some (most?) 3d modeling programs, I am not sure if
      > this is doable in jitter. Namely, I am hoping to have 3d objects floating in
      > space and when they move into the area where a [preferably invisible]
      > texture is being projected (a texture of a quicktime movie for instance),
      > their body will reflect a particular part of this otherwise invisible
      > texture. So, in other words, if a 3d object finds its way into the top-right
      > corner of the projected texture (which would be invisible otherwise), then
      > their body would reflect that top-right corner, in effect becoming
      > doubly-textured object.
      >
      > This would in effect seem as if the invisible texture in question is being
      > subtracted against the shapes of 3d objects, allowing only to see parts of
      > the texture where 3d objects reside. Hence, my [awkward?] title :-).
      >
      > Any help in this matter is most appreciated!
      >
      > Ivica Ico Bukvic, D.M.A.
      > Composition, Music Technology, CCTAD, CHCI
      > Virginia Tech
      > Dept. of Music - 0240
      > Blacksburg, VA 24061
      > (540) 231-1137
      > (540) 231-5034 (fax)
      > ico@vt.edu
      > http://www.music.vt.edu/people/faculty/bukvic/
      > http://ico.bukvic.net
      >
      >
      >
      >
    • Jun 01 2007 | 5:19 am
      Awesome! Many thanks for this!
      BTW, regarding the second option, do you mind elaborating upon this one a
      bit more? Are you suggesting simply calculating coordinates of the object in
      respect to floating texture area and based upon that extracting a portion of
      the texture from the texture matrix and then mapping it onto the object in
      question?
      Best wishes,
      Ico
      > -----Original Message-----
      > From: jitter-bounces@cycling74.com [mailto:jitter-bounces@cycling74.com]
      > On Behalf Of Wesley Smith
      > Sent: Friday, June 01, 2007 12:43 AM
      > Subject: Re: [jitter] question about subtractive texturing
      >
      > Did you see my sharing is fun projective texture patch from last
      > night? This could serve your purpose if you want the projected
      > texture to be arbitrarily located in the scene. You'd have to change
      > things a little of course to get multitexturing, but it could easily
      > be done. The other option which is less flexible but easier on the
      > GPU and more straightforward to understand is to use object space
      > texture coordinates with a border color of black and a @wrap
      > clampborder.
      >
      > wes
      >
      > On 5/31/07, Ivica Ico Bukvic wrote:
      > > Not sure if the title is an official term but at 12am I honestly could
      > not
      > > think of a better way to express this.
      > >
      > > While this is doable in some (most?) 3d modeling programs, I am not sure
      > if
      > > this is doable in jitter. Namely, I am hoping to have 3d objects
      > floating in
      > > space and when they move into the area where a [preferably invisible]
      > > texture is being projected (a texture of a quicktime movie for
      > instance),
      > > their body will reflect a particular part of this otherwise invisible
      > > texture. So, in other words, if a 3d object finds its way into the top-
      > right
      > > corner of the projected texture (which would be invisible otherwise),
      > then
      > > their body would reflect that top-right corner, in effect becoming
      > > doubly-textured object.
      > >
      > > This would in effect seem as if the invisible texture in question is
      > being
      > > subtracted against the shapes of 3d objects, allowing only to see parts
      > of
      > > the texture where 3d objects reside. Hence, my [awkward?] title :-).
      > >
      > > Any help in this matter is most appreciated!
      > >
      > > Ivica Ico Bukvic, D.M.A.
      > > Composition, Music Technology, CCTAD, CHCI
      > > Virginia Tech
      > > Dept. of Music - 0240
      > > Blacksburg, VA 24061
      > > (540) 231-1137
      > > (540) 231-5034 (fax)
      > > ico@vt.edu
      > > http://www.music.vt.edu/people/faculty/bukvic/
      > > http://ico.bukvic.net
      > >
      > >
      > >
      > >
    • Jun 01 2007 | 5:32 am
      Here's a start. BTW, I made a mstake in my previous email. The borer
      color should be 1 1 1 1.
      wes