#version 450 core

#pragma include ./tail_update_shared.glsl
#pragma include ../misc/global.glsl

in VertexData vertexData[];

layout (points) in;
layout (points, max_vertices = 1) out;

out vec2 outTail0;
out vec2 outTail1;
out vec2 outTail2;
out vec2 outTail3;
out vec2 outTail4;
out vec2 outTail5;

vec2 move(vec2 ref, vec2 point) {
    vec2  dir   = ref - point;
    float len   = length(dir);
    float diff  = max(len - TAIL_LEN, 0.0);
    float force = min(TAIL_FORCE * diff * uGlobal.delta, diff);

    return point + normalize(dir) * force;
}

void main() {
    VertexData d = vertexData[0];

    outTail0 = d.pos;

    outTail1 = move(d.pos,     d.tail[1]);
    outTail2 = move(d.tail[1], d.tail[2]);
    outTail3 = move(d.tail[2], d.tail[3]);
    outTail4 = move(d.tail[3], d.tail[4]);
    outTail5 = move(d.tail[4], d.tail[5]);

    EmitVertex();
    EndPrimitive();
}