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#version 330 core
#extension GL_ARB_enhanced_layouts : enable
#extension GL_ARB_shading_language_420pack : enable
const vec3[] pyramid = vec3[]( // four-sided
vec3(0, 0, 0), // Apex
vec3(-1, 1, 1), // Back-left
vec3(-1, -1, 1), // Front-left
vec3(1, 1, 1), // Back-right
vec3(1, -1, 1) // Front-right
);
uniform mat4 viewProjection;
uniform vec3 viewPoint;
uniform float arc;
in vec3 position[];
in vec3 direction[];
in float size[];
in float cosarc[];
layout(points) in;
layout(triangle_strip, max_vertices = 8) out;
out vec4 geo_centre;
out vec4 geo_direction;
vec3
perp(vec3 a)
{
return normalize(a.x != 0 ? vec3((a.y + a.z) / -a.x, 1, 1)
: a.y != 0 ? vec3(1, (a.x + a.z) / -a.y, 1)
: vec3(1, 1, (a.x + a.y) / -a.z));
}
void
doVertex(vec4 ndcpos)
{
gl_Position = ndcpos;
geo_centre = vec4(position[0], size[0]);
geo_direction = vec4(direction[0], cosarc[0]);
EmitVertex();
}
void
main()
{
const float base = size[0] * tan(arc / 2);
const vec3 offx = perp(direction[0]);
const vec3 offy = cross(direction[0], offx);
vec4 out_py[pyramid.length()];
for (int i = 0; i < pyramid.length(); ++i) {
const vec3 p = pyramid[i];
const vec3 edge = (offx * base * p.x) + (offy * base * p.y) + (direction[0] * size[0] * p.z);
out_py[i] = viewProjection * (gl_in[0].gl_Position + vec4(edge, 1));
}
doVertex(out_py[3]);
doVertex(out_py[0]);
doVertex(out_py[1]);
doVertex(out_py[2]);
doVertex(out_py[3]);
doVertex(out_py[4]);
doVertex(out_py[0]);
doVertex(out_py[2]);
EndPrimitive();
}
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