Angus Dorbie (dorbie++at++bitch.reading.sgi.com)
Wed, 22 Jan 1997 16:50:40 +0000
The way to achieve perspective correct parameter mapping is to use
a 1D texture and map the texture coordinate to the amplitude
parameter. This is extremely powerfull when you consider that
you can modify the texture image to map any scale in a linear
manner to your vertical scale. This could for example include a
suitable logaritmic scale markers, and all you have to do is
specify texture coords instead of colours. You can band the data
or use alpha to isolate a particular height and your still only
using a 1D image.
If you use a 2D image you could do all the above but map an
additional parameter in your data and use alpha to clip to areas
of this parameter.
Cheers,
Angus.
On Jan 22, 8:35am, SCOTT OFRIEL wrote:
> Subject: Re: Getting Gouraud Color
> Perhaps a little more explanation of our situation will help. Thanks for
> looking in.
>
> What I am doing is a 3D type bar graph where each bar represents a radar's
> range and/or doppler gate (range (x-axis) vs. doppler (y-axis)). The height
> of the gate (z-axis) represents the amplitude of the signal in that
particular
> gate. I would like to have the amplitude of each gate related to color where
> blue is the lowest energy and red is the highest. The line I was referring
> to is the z-axis which is the amplitude axis and is Gouraud shaded from blue
> to red.
>
> For example, if a the max signal strength was 80db and a gates value was 80
db
> that bar would be Gouraud shaded from blue to red. If the signal strength
for
> a gate was 40db the bar would have the same color as the z-axis, from blue to
> the color of at the mid-point of the z-axis.
>
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