public override float IntensityAt(Vector3 position, Vector3 surfaceNormal, Scene scene, out Color color)
{
color = _color;
Vector3 direction = position - _position;
float distance = direction.Length();
var ray = new Ray(_position, direction);
bool visible = scene.IsVisible(ray, distance);
if (!visible) return 0;
float intensity = _intensity * _rangeSquared / (_rangeSquared + distance * distance);
float normalAdjustedIntensity = intensity *
Vector3.Dot(surfaceNormal, Vector3.Zero - direction.Normalized());
return Math.Max(normalAdjustedIntensity, 0);
}