From: Angus Dorbie (dorbie++at++sgi.com)
Date: 08/31/2000 14:22:02
Angus Dorbie wrote:
>
> OK, just stick with the subload call
> xsrc = 0
> ysrc = 0
> srcwid = 760
> xdst = 0
> ydst = 0
> xsize = 760
> ysize = 486
P.S. ysize is not evenly divisible by 8 so on iR this may cause a
problem. A ysize of 488 with the appropriate data size would be the
recommended choice for this platform.
CHeers,Angus.
>
> Satheesh Ganapathi Subramanian wrote:
> >
> > Hi Angus,
> >
> > Thanks for your detailed explanation. But I've been having some problems
> > trying to get the
> >
> > I tried doing a subload with this understanding. My destination texture
> > has a dummy data filled with all blue (1024x512). My subload is dummy data
> > with all white (760x486). When I do a subload, what I expected was that
> > the portion of the texture that was subloaded would be white and the rest
> > of it would be blue. What I got instead was that the portion of the
> > texture that was subloaded was white but the rest of the texture was
> > having corrupt data. I couldn't figure out why that was happening.
> >
> > Also, I've another question. What is the difference between using
> > pfTexture::subload() and using pfTexture::setLoadImage() inconjunction
> > with setLoadOrigin() and setLoadSize() with the texture format enabled for
> > PFTEX_SUBLOAD_FORMAT and PFTEX_BASE_AUTO_SUBLOAD. I tried both the
> > approaches and the result was exactly the same as described above.
> >
> > Again, if there is some sample code that can illustrate the use of
> > pfTexture::subload() it would be of great help.
> >
> > Thanks
> > Satheesh
> >
> > >The key thing to note here is that the source image may be a different
> > >size form the destination image. In addition the image being subloaded
> > >may not occupy the full width of the source image and may not be
> > >positioned at the origin of the source image.
> > >
> > >If you consider this problem it becomes clear that you need to specify
> > >the location of the subload in the destination image, the overall width
> > >of the source image and the width and height of the subload from the
> > >source image, and the position of the origin of the subload in the
> > >source image.
> > >
> > >The height of the source image isn't needed because the image is stored
> > >column minor, row major in OpenGL, but in order to properly address
> > >height you need to know the image width for the stored source image
> > >unless you are subloading a full width image in which case xsize is all
> > >you need.
> > >
> > >So, srcwid is needed to support source images of widths which do not
> > >match the width of the image in texture memory, xsrc and ysrc is the
> > >origin of the download in the source image (which doesn't have to be the
> > >same as the origin in the destination image).
> > >
> > >There is a degree of redundancy because an application could simply
> > >adjust the pointer to address the appropriate pixel of the source image
> > >and zero the xsrc and ysrc values, but that's more tricky for the
> > >application to code for I suppose.
> > >
> > >Strictly speaking the manual description is wrong w.r.t. srcwidth.
> > >
> > >Cheers,Angus.
> > >
> > >Satheesh Ganapathi Subramanian wrote:
> > >>
> > >> Hi Performers,
> > >>
> > >> I'm trying to use pfTexture::subload or pfSubLoadTex and I'm not able to
> > >> understand the meaning of - srcwidth, xsrc, ysrc - in the list of
> > >> paramenters to that function. I'm creating an image buffer (unsigned
> > >> int*), the data in which keeps changing every frame. I would like to load
> > >> this into texture memory using pfTexture::subload. It would be great if
> > >> someone can tell me what each parameter of the function call means. I'm
> > >> not able to get much out of the man pages.
> > >>
> > >> If anyone has some sample code that they can share, explaining how to use
> > >> this function, it would be of immense use.
> > >>
> > >> Thanks
> > >> Satheesh
> > >>
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> > >
> > >--
> > >For Performer+OpenGL tutorials http://www.dorbie.com/
> > >
> > >"In the middle of difficulty lies opportunity."
> > > --Albert Einstein
> > >
> >
> > ===================== members.xoom.com/malargal ========================
> >
> > Satheesh GanapathiSubramanian
> > gsat++at++evl.uic.edu
> > Work: Home:
> > Research Assistant 901, S.Ashland Av, Apt# 107-A
> > The Electronic Visualization Laboratory Chicago, IL-60607
> > 851, S.Morgan St., Room# 1120 SEO
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>
> --
> For Performer+OpenGL tutorials http://www.dorbie.com/
>
> "In the middle of difficulty lies opportunity."
> --Albert Einstein
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-- For Performer+OpenGL tutorials http://www.dorbie.com/"In the middle of difficulty lies opportunity." --Albert Einstein
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