layout(vertices = 3) out;

in vec3 vWorldPos[];
in vec3 vNormal[];

out vec3 tcWorldPos[];
out vec3 tcNormal[];

uniform float m_TessellationLevel;
uniform vec3  g_CameraPosition;

void main() {
    tcWorldPos[gl_InvocationID] = vWorldPos[gl_InvocationID];
    tcNormal[gl_InvocationID]   = vNormal[gl_InvocationID];

    if (gl_InvocationID == 0) {
        vec3  center = (vWorldPos[0] + vWorldPos[1] + vWorldPos[2]) / 3.0;
        float dist   = distance(g_CameraPosition, center);

        // Maximum subdivision close-up, falls to 1 at 64 m
        float level  = mix(m_TessellationLevel, 1.0, clamp(dist / 64.0, 0.0, 1.0));
        level = max(1.0, level);

        gl_TessLevelOuter[0] = level;
        gl_TessLevelOuter[1] = level;
        gl_TessLevelOuter[2] = level;
        gl_TessLevelInner[0] = level;
    }
}