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fgdata/Shaders/terrain-overlay-ALS.geom

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// -*-C++-*-
#version 120
#extension GL_EXT_geometry_shader4 : enable
#define MAX_LAYERS 8
#define MIN_LAYERS 2
#define MAX_MINUS_MIN_LAYERS 6
uniform float overlay_max_height;
varying in vec3 v_normal[3];
varying out vec2 g_rawpos;
varying out float g_distance_to_eye;
varying out vec3 g_normal;
varying out float g_altitude;
flat varying out float g_layer;
float min3(in float a, in float b, in float c)
{
float m = a;
if (m > b) m = b;
if (m > c) m = c;
return m;
}
void main()
{
float distances[3];
distances[0] = -(gl_ModelViewMatrix * gl_PositionIn[0]).z;
distances[1] = -(gl_ModelViewMatrix * gl_PositionIn[1]).z;
distances[2] = -(gl_ModelViewMatrix * gl_PositionIn[2]).z;
float minDistance = min3(distances[0], distances[1], distances[2]);
//float avgDistance = (distances[0]+distances[1]+distances[2])*0.33;
int numLayers = MIN_LAYERS + int((1.0 - smoothstep(250.0, 5000.0, minDistance)) * float(MAX_MINUS_MIN_LAYERS));
float deltaLayer = 1.0 / float(numLayers);
float currDeltaLayer = 1.5 * deltaLayer;// * 0.5;
for (int layer = 0; layer < numLayers; ++layer) {
for (int i = 0; i < 3; ++i) {
vec4 pos = gl_PositionIn[i] + vec4(v_normal[i] * currDeltaLayer * overlay_max_height, 0.0);
g_rawpos = gl_PositionIn[i].xy;
g_distance_to_eye = distances[i];
g_layer = currDeltaLayer;
g_normal = v_normal[i];
g_altitude = gl_PositionIn[i].z;
gl_Position = gl_ModelViewProjectionMatrix * pos;
gl_TexCoord[0] = gl_TexCoordIn[i][0];
EmitVertex();
}
EndPrimitive();
currDeltaLayer += deltaLayer;
}
}