HI Wojciech,
Hi Sebastian,
Perhaps your GPU can use doubles ? Many of them can these days. You
may also try to refactor the code to use pairs of floats (as base and
offset) which in theory may be almost as precise as double. It may be
however very tricky for such non-linear math as geographic projections...
I've tried. Unfortunately the trigonometric functions are not available
for double precision. And I'm clueless with the two-float mechanism and
trigonometric functions.
Also I guess I would have to push double matrices, and I don't know how
OSG is handling them. I can recall Robert explaining that they are
indeed pushed as double matrices, so the driver would cut them to float.
cheers
Sebastian
Cheers,
Wojtek
2013/12/5 Sebastian Messerschmidt <sebastian.messerschm...@gmx.de
<mailto:sebastian.messerschm...@gmx.de>>
Hi,
I managed to get the local heights.
After realizing, that the osg_ViewMatrix * gl_ModelViewMatrix will
bring me into world space I was able to use a XYZ_to_latlonheight
function in the vertex shader.
There is only one catch with this: precision. It seems that the
float matrices will simply cut away to much precision so I get
massive flickering.
Anyone any idea how to solve, improve this? In the end I simply
want to draw a water surface where the height of the geometry is
below a certain threshold. My problem here are the fragment where
the height is almost equal to the threshold.
I also tried to move the LLH-calculation to the fragment shader,
but it didn't help.
example:
vertex-shader:
out vec3 lat_lon_height;
vec3 XYZ_to_llh(vec3 ws_pos)
{
//from osgEarth
float X = xyz.x;
float Y = xyz.y;
float Z = xyz.z;
float _radiusEquator = 6378137.0;
float _radiusPolar = 6356752.3142;
float flattening = (_radiusEquator-_radiusPolar)/_radiusEquator;
float _eccentricitySquared = 2*flattening - flattening*flattening;
float p = sqrt(X*X + Y*Y);
float theta = atan(Z*_radiusEquator , (p*_radiusPolar));
float eDashSquared = (_radiusEquator*_radiusEquator -
_radiusPolar*_radiusPolar)/(_radiusPolar*_radiusPolar);
float sin_theta = sin(theta);
float cos_theta = cos(theta);
float latitude = atan( (Z +
eDashSquared*_radiusPolar*sin_theta*sin_theta*sin_theta), (p -
_eccentricitySquared*_radiusEquator*cos_theta*cos_theta*cos_theta) );
float longitude = atan(Y,X);
float sin_latitude = sin(latitude);
float N = _radiusEquator / sqrt( 1.0 -
_eccentricitySquared*sin_latitude*sin_latitude);
float height = p/cos(latitude) - N;
return vec3(longitude, latitude, height);
}
void main()
{
vec3 ws_pos = osg_ViewMatrix * osg_ModelViewMatrix * gl_Vertex;
llh = XYZ_to_llh(ws_pos);
...
}
fragment:
void main()
{
if (llh.z < 10.0)
{
gl_FragColor = vec4(1,0,0,1);
}
else
{
gl_FragColor = color;
}
}
Hi,
I have a osgDEM produced geocentric database.
I looked into the geometryTechnique implementation to see if I
somehow can access the height of the vertices above the
ellipsoid in the vertex shader.
Unfortunately I don't have any idea how to calculate this from
the give matrices. Is this information somehow available at all?
My plan is to overwrite some of the functionality in the
geometryTechnique to pass the appropriate matrices to the shader.
Anyone having an idea?
_______________________________________________
osg-users mailing list
osg-users@lists.openscenegraph.org
<mailto:osg-users@lists.openscenegraph.org>
http://lists.openscenegraph.org/listinfo.cgi/osg-users-openscenegraph.org
_______________________________________________
osg-users mailing list
osg-users@lists.openscenegraph.org
<mailto:osg-users@lists.openscenegraph.org>
http://lists.openscenegraph.org/listinfo.cgi/osg-users-openscenegraph.org
_______________________________________________
osg-users mailing list
osg-users@lists.openscenegraph.org
http://lists.openscenegraph.org/listinfo.cgi/osg-users-openscenegraph.org
_______________________________________________
osg-users mailing list
osg-users@lists.openscenegraph.org
http://lists.openscenegraph.org/listinfo.cgi/osg-users-openscenegraph.org
