void
cGrCloudLayer::build( ssgSimpleState *cloud_state, float span, float elevation, float thickness, float transition )
{
layer_span = span;
layer_asl = elevation;
layer_thickness = thickness;
layer_transition = transition;
scale = 4000.0;
last_lon = last_lat = -999.0f;
last_x = last_y = 0.0f;
sgVec2 base;
sgSetVec2( base, (float)grRandom(), (float)grRandom() );
// build the cloud layer
sgVec4 color;
sgVec3 vertex;
sgVec2 tc;
const float layer_scale = layer_span / scale;
const float mpi = SG_PI/4;
const float alt_diff = layer_asl * 1.5f;
for (int i = 0; i < 4; i++)
{
if ( layer[i] != NULL )
{
layer_transform->removeKid(layer[i]); // automatic delete
}
vl[i] = new ssgVertexArray( 10 );
cl[i] = new ssgColourArray( 10 );
tl[i] = new ssgTexCoordArray( 10 );
sgSetVec3( vertex, layer_span*(i-2)/2, -layer_span,
(float)(alt_diff * (sin(i*mpi) - 2)) );
sgSetVec2( tc, base[0] + layer_scale * i/4, base[1] );
sgSetVec4( color, 1.0f, 1.0f, 1.0f, (i == 0) ? 0.0f : 0.15f );
cl[i]->add( color );
vl[i]->add( vertex );
tl[i]->add( tc );
for (int j = 0; j < 4; j++)
{
sgSetVec3( vertex, layer_span*(i-1)/2, layer_span*(j-2)/2,
(float)(alt_diff * (sin((i+1)*mpi) + sin(j*mpi) - 2)) );
sgSetVec2( tc, base[0] + layer_scale * (i+1)/4,
base[1] + layer_scale * j/4 );
sgSetVec4( color, 1.0f, 1.0f, 1.0f,
( (j == 0) || (i == 3)) ?
( (j == 0) && (i == 3)) ? 0.0f : 0.15f : 1.0f );
cl[i]->add( color );
vl[i]->add( vertex );
tl[i]->add( tc );
sgSetVec3( vertex, layer_span*(i-2)/2, layer_span*(j-1)/2,
(float)(alt_diff * (sin(i*mpi) + sin((j+1)*mpi) - 2)) );
sgSetVec2( tc, base[0] + layer_scale * i/4,
base[1] + layer_scale * (j+1)/4 );
sgSetVec4( color, 1.0f, 1.0f, 1.0f,
((j == 3) || (i == 0)) ?
((j == 3) && (i == 0)) ? 0.0f : 0.15f : 1.0f );
cl[i]->add( color );
vl[i]->add( vertex );
tl[i]->add( tc );
}
sgSetVec3( vertex, layer_span*(i-1)/2, layer_span,
(float)(alt_diff * (sin((i+1)*mpi) - 2)) );
sgSetVec2( tc, base[0] + layer_scale * (i+1)/4,
base[1] + layer_scale );
sgSetVec4( color, 1.0f, 1.0f, 1.0f, (i == 3) ? 0.0f : 0.15f );
cl[i]->add( color );
vl[i]->add( vertex );
tl[i]->add( tc );
layer[i] = new ssgVtxTable(GL_TRIANGLE_STRIP, vl[i], NULL, tl[i], cl[i]);
layer_transform->addKid( layer[i] );
layer[i]->setState( cloud_state );
}
// force a repaint of the sky colors with arbitrary defaults
repaint( color );
}
void cGrSky::modifyVisibility( float alt, float time_factor )
{
float effvis = visibility;
for ( int i = 0; i < clouds.getNum (); ++i )
{
cGrCloudLayer *cloud = clouds.get(i);
if ( cloud->isEnabled() )
{
float asl = cloud->getElevation();
float thickness = cloud->getThickness();
float transition = cloud->getTransition();
float ratio = 1.0;
if ( alt < asl - transition )
{
// below cloud layer
ratio = 1.0;
}
else if ( alt < asl )
{
// in lower transition
ratio = (asl - alt) / transition;
}
else if ( alt < asl + thickness )
{
// in cloud layer
ratio = 0.0;
}
else if ( alt < asl + thickness + transition )
{
// in upper transition
ratio = (alt - (asl + thickness)) / transition;
}
else
{
// above cloud layer
ratio = 1.0;
}
// accumulate effects from multiple cloud layers
effvis *= ratio;
if ( ratio < 1.0 )
{
if ( ! in_puff )
{
// calc chance of entering cloud puff
double rnd = grRandom();
double chance = rnd * rnd * rnd;
if ( chance > 0.95 )
{
in_puff = true;
puff_length = grRandom() * 2.0; // up to 2 seconds
puff_progression = 0.0;
}
}
if ( in_puff )
{
// modify actual_visibility based on puff envelope
if ( puff_progression <= ramp_up )
{
double x = 0.5 * SGD_PI * puff_progression / ramp_up;
double factor = 1.0 - sin( x );
effvis = (float)(effvis * factor);
}
else if ( puff_progression >= ramp_up + puff_length )
{
double x = 0.5 * SGD_PI *
(puff_progression - (ramp_up + puff_length)) /
ramp_down;
double factor = sin( x );
effvis = (float)(effvis * factor);
}
else
{
effvis = 0.0;
}
puff_progression += time_factor;
if ( puff_progression > puff_length + ramp_up + ramp_down)
{
in_puff = false;
}
}
// never let visibility drop below 25 meters
if ( effvis <= 25.0 )
{
effvis = 25.0;
}
}
}
} // for
effective_visibility = effvis;
}
