// #include "res://addons/rokojori_action_library/Runtime/Shading/Library/LineVFX/LineVFX-Includes.gdshaderinc"
// #include "res://addons/rokojori_action_library/Runtime/Shading/Library/LineVFX/LineVFX-Variables.gdshaderinc"
// #include "res://addons/rokojori_action_library/Runtime/Shading/Library/LineVFX/LineVFX-Vertex.gdshaderinc"

// vec3 translation; mat3 rotation;
 
  if ( positionInterpolationMode == 0 )
  {
    translation = mix( startPosition, endPosition, t );
  }
  else if ( positionInterpolationMode == 1 )
  {
    float controlLength = length( endPosition - startPosition ) * bezierCurvature; 
    vec3 c0 = startPosition + normalize( startForward ) * controlLength;
    vec3 c1 = endPosition - normalize( endForward ) * controlLength;

    translation = cubicBezier( t, startPosition, c0, c1, endPosition );
  }
  else if ( positionInterpolationMode == 2 )
  {
    float controlLength = length( endPosition - startPosition ) * rationalCurvature; 
    vec3 c0 = startPosition + normalize( startForward ) * controlLength;
    vec3 c1 = endPosition - normalize( endForward ) * controlLength;

    translation = rationalCubicBezier( t, 
      startPosition, c0, c1, endPosition,
      1.0, rationalWeighting, rationalWeighting, 1.0
    );

  }
  

  if ( rotationInterpolationMode == 0 )
  {
    vec3 forward = normalize( mix( startForward, endForward, t ) );
    vec3 up = normalize( mix( startUp, endUp, t ) );
    rotation = lookRotation( forward, up );

  }
  else if ( rotationInterpolationMode == 1 )
  {
    vec4 startRotation = quaternionFromLookRotation( startForward, startUp );
    vec4 endRotation   = quaternionFromLookRotation( endForward, endUp );

    vec4 qRotation = quaternionSlerp( startRotation, endRotation, t );
    rotation = quaternionToRotationMatrix( qRotation );
  }
  else if ( rotationInterpolationMode == 2 )
  {
    
    float controlLength = length( endPosition - startPosition ) * bezierCurvature; 
    vec3 c0 = startPosition + normalize( startForward ) * controlLength;
    vec3 c1 = endPosition - normalize( endForward ) * controlLength;

    vec3 forward = normalize( cubicBezierDerivative( t, startPosition, c0, c1, endPosition ) );
    vec3 up = normalize( mix( startUp, endUp, t ) );
    rotation = lookRotation( forward, up );
  }
  else if ( rotationInterpolationMode == 3 )
  {
    vec3 lineDirection = normalize( endPosition - startPosition );
    vec3 forward = t < 0.5 ? mix( startForward, lineDirection, t * 2.0 ) :
                             mix( lineDirection, endForward, ( t - 0.5 ) * 2.0 );
    vec3 up = normalize( mix( startUp, endUp, t ) );
    rotation = lookRotation( forward, up );
  }
  else if ( rotationInterpolationMode == 4 )
  {
    bool isStart = t < 0.5;
    vec3 lineDirection = normalize( endPosition - startPosition );
    vec3 centerUp = normalize( mix( startUp, endUp, 0.5 ) );

    vec3 forwardA = isStart ? startForward : lineDirection;
    vec3 forwardB = isStart ? lineDirection : endForward;

    vec3 upA = isStart ? startUp : centerUp;
    vec3 upB = isStart ? centerUp : endUp;

    vec4 rotationA = quaternionFromLookRotation( forwardA, upA );
    vec4 rotationB   = quaternionFromLookRotation( forwardB, upB );

    float rt = isStart ? ( t * 2.0 ) : ( ( t -0.5 ) * 2.0 );

    vec4 qRotation = quaternionSlerp( rotationA, rotationB, rt );
    rotation = quaternionToRotationMatrix( qRotation );
  }