Re: Rasterize Camera Transform and alpha channel

[James W. W. <ja...@fr...>]

Roger Holmes <rog...@mi...> wrote:

>We have been using Q3RasterizeCameraTransform_New for some time to
>draw a square with a background pattern on it, we have also allowed
>the user to do the same thing for a foreground pattern, though that
>was fairly useless as it hid all the 3D Objects. I have now allowed
>patterns with an alpha channel to be used for the foreground, but
>nothing appears.
>
>I have traced the problem down to ir_geom_transparent_add, which
>multiplies all the points
>by the Local To Camera matrix (which is a unit matrix at this time),
>and then checks if any of the
>z coordinates are <= zero. None are, they are all 0.0001 (Peter tells
>me this is so that they are in front of the clipping plane). Because
>now are <= 0 the routines simply returns (presumably it thinks
>the triangle is clipped). If I comment out the test, all is well.
>
>Should this be fixed in ir_geom_transparent_add or should the
>Rasterize Camera Transform set the Local To Camera matrix up
>differently?

The latter.  Camera coordinates are supposed to have the camera 
pointing down the negative z axis.  I have committed a fix.  It seems 
to work right in Geom Test if I use a z value of .0001, but let me 
know if you see any problems.

-- 
   James W. Walker, Innoventive Software LLC
   <http://www.frameforge3d.com/>