float dist = sqrt(deltaxy.x * deltaxy.x + deltaxy.y * deltaxy.y + alt_agl * alt_agl); //could use function 'distance' instead, might be better?
pos.z = (-0.9*75)*alt_agl/dist + 0.05 * vertex.z ; //if the shadow is more than about 75 meters from the aircraft it disappears so we are going to just keep it right at 75 m. & make it smaller to simulate greater distance.
Thorsten wrote in Tue Mar 21, 2017 10:52 am:Some remarks - you ought to give your shadow plane model some alpha. The fragment shader actually sets alpha, but that won't be used by the GPU unless it starts the draw expecting alpha, so the correct handling needs to be triggered.
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pos.z = (-0.9*75)*alt_agl/dist + 0.05 * vertex.z ; //if the shadow is more than about 75 meters from the aircraft it disappears so we are going to just keep it right at 75 m. & make it smaller to simulate greater distance.
This isn't fixing distance though, it's fixing altitude to something that's distance dependent. Since there'll be vertices farther away from the origin in the shadow, this fixes near and far parts of the shadow to different altitudes and likely is what tilts your projection from flat.
Main question I guess is - does it cause breakage for existing models?
I actually remember having tested various combinations of pitch and roll (there's a test shot in the wiki) and it worked out okay, so I wonder whether you've just combined two different ways of defining angles/matrices into another correctly working solution.
Thorsten wrote in Tue Mar 21, 2017 10:52 am:Main question I guess is - does it cause breakage for existing models?
This does have one problem that I can't solve right now: When the shadow is more distant than 75 meters and the 'keep at 75 m. but shrink the size' illusion kicks in, the shadow is no longer parallel with the ground.
// -*-C++-*-
#version 120
uniform float hazeLayerAltitude;
uniform float terminator;
uniform float terrain_alt;
uniform float overcast;
uniform float ground_scattering;
uniform float eye_alt;
uniform float moonlight;
uniform float alt_agl;
uniform float pitch;
uniform float roll;
uniform float gear_clearance;
const float EarthRadius = 5800000.0;
const float terminator_width = 200000.0;
void rotationMatrixPR(in float sinRx, in float cosRx, in float sinRy, in float cosRy, out mat4 rotmat)
{
rotmat = mat4( cosRy , sinRx * sinRy , cosRx * sinRy, 0.0,
0.0 , cosRx , -sinRx , 0.0,
-sinRy, sinRx * cosRy, cosRx * cosRy , 0.0,
0.0 , 0.0 , 0.0 , 1.0 );
}
/*
//Experimental - not used for now. Seems to work functionally the same as rotationMatrixPR
void rotationMatrixRP(in float sinRx, in float cosRx, in float sinRy, in float cosRy, out mat4 rotmat)
{
rotmat = mat4( cosRy , sinRx * sinRy , -cosRx * sinRy, 0.0,
0.0 , cosRx , sinRx , 0.0,
sinRy, -sinRx * cosRy, cosRx * cosRy , 0.0,
0.0 , 0.0 , 0.0 , 1.0 );
}
*/
float light_func (in float x, in float a, in float b, in float c, in float d, in float e)
{
if (x < -15.0) {return 0.0;}
return e / pow((1.0 + a * exp(-b * (x-c)) ),(1.0/d));
}
void main()
{
gl_TexCoord[0] = gl_TextureMatrix[0] * gl_MultiTexCoord0;
vec4 ep = gl_ModelViewMatrixInverse * vec4(0.0,0.0,0.0,1.0);
vec3 relPos = gl_Vertex.xyz - ep.xyz;
// compute the strength of light
float vertex_alt = max(gl_Vertex.z,100.0);
float scattering = ground_scattering + (1.0 - ground_scattering) * smoothstep(hazeLayerAltitude -100.0, hazeLayerAltitude + 100.0, vertex_alt);
vec3 lightFull = (gl_ModelViewMatrixInverse * gl_LightSource[0].position).xyz;
vec3 lightHorizon = normalize(vec3(lightFull.x,lightFull.y, 0.0));
float yprime = -dot(relPos, lightHorizon);
float yprime_alt = yprime - sqrt(2.0 * EarthRadius * vertex_alt);
float earthShade = 0.6 * (1.0 - smoothstep(-terminator_width+ terminator, terminator_width + terminator, yprime_alt)) + 0.4;
float lightArg = (terminator-yprime_alt)/100000.0;
vec4 light_diffuse;
light_diffuse.b = light_func(lightArg, 1.330e-05, 0.264, 3.827, 1.08e-05, 1.0);
light_diffuse.g = light_func(lightArg, 3.931e-06, 0.264, 3.827, 7.93e-06, 1.0);
light_diffuse.r = light_func(lightArg, 8.305e-06, 0.161, 3.827, 3.04e-05, 1.0);
light_diffuse.a = 1.0;
light_diffuse = light_diffuse * scattering;
float shade_depth = 1.0 * smoothstep (0.6,0.95,ground_scattering) * (1.0-smoothstep(0.1,0.5,overcast)) * smoothstep(0.4,1.5,earthShade);
light_diffuse.rgb = light_diffuse.rgb * (1.0 + 1.2 * shade_depth);
//experiment
light_diffuse.b = 1.0;
light_diffuse.g = 1.0;
light_diffuse.r = 1.0;
light_diffuse.a = 1.0;
//prepare rotation matrix
mat4 RotMatPR;
mat4 RotMatPR_tr;
float _roll = roll;
//if (_roll>90.0 || _roll < -90.0) //making roll=-roll when >90 is no longer necessary thanks to fix with transpose of rotation matrix.
//{_roll = -_roll;}
float cosRx = cos(radians(-_roll));
float sinRx = sin(radians(-_roll));
float cosRy = cos(radians(pitch));
float sinRy = sin(radians(pitch));
rotationMatrixPR(sinRx, cosRx, sinRy, cosRy, RotMatPR);
//rotationMatrixRP(sinRx, cosRx, sinRy, cosRy, RotMatPR);
RotMatPR_tr=transpose(RotMatPR); //RotMatPR works fine if pitch =0 or roll=0 but if say pitch=35 and roll=60 the rotation is all wrong. transpose(RotMatPR) however works perfectly.
// project the shadow onto the ground
//vec4 vertex = RotMatPR * gl_Vertex;
vec4 vertex = RotMatPR_tr * gl_Vertex;
vec4 pos = vertex;
vec2 deltaxy = lightFull.xy * 0.95* (alt_agl + vertex.z + gear_clearance)/lightFull.z; //This is the 'actual' location, taking into a account the full 3-D structure of the aircraft
vec2 deltazeroxy = lightFull.xy * 0.95* (alt_agl + gear_clearance)/lightFull.z; //Instead of using the exact z value of this particularly point to determine the distance of the shadow & reposition & shrink it appropriately, we'll just use the origin (0,0,0) of the model instead. This avoids a problem below, where varying vertex.z in deltaxy and then using deltaxy to calculate dist caused the shadow to sort of slant upwards, thanks to the varying z values used
float dist = sqrt(deltazeroxy.x * deltazeroxy.x + deltazeroxy.y * deltazeroxy.y + alt_agl * alt_agl); //could use function 'distance' instead, might be better?
if (dist < 75)
{
pos.z = -0.9 * alt_agl + 0.05 * vertex.z;
//pos.z = 0.05 * (vertex.z + gear_clearance);
pos.xy -= deltaxy;
}
else
{
//The code below to shrink the shadow while keeping it 75 m. away has some issues that need to be fixed. Making the shadow shrink at x^2 rate partly to cover up this problem until it can be solved . . .
//The problem is that the aircraft isn't flat/parallel to the ground any more, but it appears to be at an angle to the ground.
//The various shrinkages perhaps mess with the angles somehow, meaning that when the animations apply the roll & pitch corrections they just don't quite work as they should
pos.z = (-0.9*75)*alt_agl/dist + 0.05 * vertex.z ; //if the shadow is more than about 75 meters from the aircraft it disappears so we are going to just keep it right at 75 m. & make it smaller to simulate greater distance.
//(-0.9*75) is the same factor for altitude we were using above when dist=75. *alt_agl/dist keeps it at the right height proportionally to simulate the location at a further distance, while actually just keeping it at 75 m. distance.
//pos.z = 0.05 * vertex.z ; //if the shadow is more than about 75 meters from the aircraft it disappears so we are going to just keep it right at 75 m. & make it smaller to simulate greater distance.
//shrink the size FIRST, THEN move where it needs to be. If you shrink later you're also shrinking the deltaxy distance moved, which doesn't work well
pos.xy = 75 / dist * pos.xy; //shrinking the size of the shadow to simulate further distance. Should be linear shrinkage but doing it ^2 for now to help ucover up the issues in code above.
pos.xy -= 75 * deltaxy/dist; // Similarly to above, * deltaxy/dist; keeps it at the right XY position proportionally to simulate the location at a further distance, while actually just keeping it at 75 m. distance.
}
// pos.z = pos.z - offset;
//if (dist>=75) pos = pos * 30/dist; //not sure why this doesn't work/ perhaps an overflow of some kind?
gl_Position = gl_ModelViewProjectionMatrix * pos;
gl_FrontColor = light_diffuse;
//light_diffuse.a=0;
gl_BackColor = gl_FrontColor;
//gl_BackColor = light_diffuse;
}
vec2 deltaxy = lightFull.xy * 0.95* (alt_agl + vertex.z + gear_clearance)/lightFull.z;
float dist = sqrt(deltaxy.x * deltaxy.x + deltaxy.y * deltaxy.y + alt_agl * alt_agl);
...
pos.z = (-0.9*75)*alt_agl/dist + 0.05 * vertex.z;
vec2 deltaxy = lightFull.xy * 0.95* (alt_agl + vertex.z + gear_clearance)/lightFull.z;
vec2 deltazeroxy = lightFull.xy * 0.95* (alt_agl + gear_clearance)/lightFull.z;
float dist = sqrt(deltazeroxy.x * deltazeroxy.x + deltazeroxy.y * deltazeroxy.y + alt_agl * alt_agl);
...
pos.z = (-0.9*75)*alt_agl/dist + 0.05 * vertex.z;
Another idea that occurred to me is that maybe shadow-vol-ALS.vert could just place the shadow flat on the ground without any further rotations needed in the model.xml file
I wonder if maybe we should be fading it out at a certain point?
Do we know why the model disappears at ~100 meters distance? It might be both simpler and better to just address that directly rather than working on this workaround.
wlbragg wrote in Tue Mar 21, 2017 10:19 pm:@flug
Is your most current shadow-vol-ALS.vert contained in the current fgaddon Sopwith files? Is that the one I would use if I wanted to test it on both the Cub and the c172p?
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