[GRASS5] Re: OGSF Color Fix ?

[Markus Neteler]

Bob,

congrats!! It seems to be fixed. Now the colors are back in
lat/long!

On Wed, Nov 29, 2000 at 12:02:51PM -0400, Bob Covill wrote:
> Markus,
> 
> I have found the start of a solution to the Lat/Long color problem. The
> problem I found was that the normals calculated for data in a lat long
> were extremely low in the Z direction. The factors that determine these
> are the relation bewteen the data Z range and a function called Longdim.
> Longdim is the largest X or Y dimension obtained by subtracting South
> from North, and west from east. In a UTM database this value is in
> meters and is generally quite large (> 100). In a Lat Long database the
> value is low. This is why the zexag is nviz is really small for a loaded
> surface (< 1).
I will try for different projections, unfortunately I am in a hurry
now. But I will upload this to cvs.
 
> I have changed how the Londim is calculated for Lat Long databases.
> Instead of subtracting degree values, I calculate the distance in
> meters. I also obtain the resolution in meters. With these values the
> zexag is a more realistic number and the normals appear to be calculated
> correctly.
> 
> I have attached two files from the ogsf library which incorporate the
> changes. The first is GS2.c which implements the above changes. The
> second is a header file gsget.h. I have changed the FNORM function in
> this file and removed the GS_global_exag varibale from it. This function
> is what unpacks the normals when they are applied. I believe that the
> global_exag is already used in calculating the normals (see gs_norms.c)
> ??
> 
> The problem with the above change to Longdim is that the data is no
> longer in the right place. Resetting the resolution changes the
> geographic coordinates. Using "Whats Here" will show how the coordinares
> have changed. Obviously the resolution has to be reset.
Mhhh. I will investigate tomorrow.
 
> Give the new lib routine a try a let me know how it works.  Any
> suggestions or comments would help.

Many thanks so far, more comments tomorrow!

Hi developers: Please re-compile the full ogsf and NVIZ then.
Please give it a try!

 Markus

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