Re: DrawPixel with simple RGB

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Angus Dorbie (dorbie++at++bitch.reading.sgi.com)
Mon, 3 Mar 1997 10:23:43 +0000

Something like this, you need to make sure that the transformed raster
position lands on the corner of the window,
Load an identity matrix onto the model stack and figure out the position
using the viewing frustum information.

    glRasterPos3f(0.001f, 1.0f, 0.001f);
    glDrawPixels(_IMAGESIZEX, _IMAGESIZEY, GL_RGBA,
                 GL_UNSIGNED_INT_8_8_8_8_EXT, imagedata);

Or you could create a simple orthographic channel with
no scene and use the above rasterpos in the draw callback
for the channel. This is how you might create the channel
for the above rasterpos and drawpixels

    chan = pfNewChan(pfGetPipe(0));
    pfChanViewport(chan6, 0.0f, _IMAGESIZEX/WIN_WIDTH,
                          0.0f, _IMAGESIZEY/WIN_HEIGHT);
    pfMakeOrthoChan(chan, 0.0f, _IMAGESIZEX, 0.0f, _IMAGESIZEY);
    pfChanNearFar(chan, NEAR, FAR);
    pfChanTravFunc(chan, PFTRAV_CULL, CullRasterChan);
    pfChanTravFunc(chan, PFTRAV_DRAW, DrawRasterChan);

Cheers,
Angus.

On Mar 1, 2:00am, Allen Bierbaum wrote:
> Subject: DrawPixel with simple RGB
> Hello all,
> I have seen several threads in the past months about how to use
> glDrawPixels with Performer. But I have not seen a difinitive code
> example demonstrating the "correct" way to do this.
>
> Could someone give me a simple example of how to display an RGB image
> (just an array of RGB floats in memory) in the lower left corner of an
> open window as a post draw function?
>
> Thanks,
> Allen
> --
>
> Allen Bierbaum
> ISU SE Lab
> Research Assistant
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>-- End of excerpt from Allen Bierbaum

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