/**
 * PANDA 3D SOFTWARE
 * Copyright (c) Carnegie Mellon University.  All rights reserved.
 *
 * All use of this software is subject to the terms of the revised BSD
 * license.  You should have received a copy of this license along
 * with this source code in a file named "LICENSE."
 *
 * @file lerp_helpers.h
 * @author drose
 * @date 2002-08-27
 */

#ifndef LERP_HELPERS_H
#define LERP_HELPERS_H

#include "directbase.h"

// The functions defined here include some trivial template functions for
// handling basic lerp computations, common to several .cxx files here.

/**
 * Applies the linear lerp computation for a single parameter.
 */
template<class NumericType>
INLINE void
lerp_value(NumericType &current_value,
           double d,
           const NumericType &starting_value,
           const NumericType &ending_value) {
  current_value = starting_value + d * (ending_value - starting_value);
}

/**
 * Applies the linear lerp computation for a single parameter, when the
 * starting value is implicit.
 *
 * This computes the new value based on assuming the prev_value represents the
 * value computed at delta prev_d.
 */
template<class NumericType>
INLINE void
lerp_value_from_prev(NumericType &current_value,
                     double d, double prev_d,
                     const NumericType &prev_value,
                     const NumericType &ending_value) {
  if (prev_d == 1.0) {
    current_value = ending_value;
  } else {
    NumericType starting_value =
      (prev_value - prev_d * ending_value) / (1.0 - prev_d);
    current_value = starting_value + d * (ending_value - starting_value);
  }
}


#endif