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direct/src/interval/cLerpInterval.cxx

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// Filename: cLerpInterval.cxx
// Created by:  drose (27Aug02)
//
////////////////////////////////////////////////////////////////////
//
// PANDA 3D SOFTWARE
// Copyright (c) 2001, Disney Enterprises, Inc.  All rights reserved
//
// All use of this software is subject to the terms of the Panda 3d
// Software license.  You should have received a copy of this license
// along with this source code; you will also find a current copy of
// the license at http://www.panda3d.org/license.txt .
//
// To contact the maintainers of this program write to
// panda3d@yahoogroups.com .
//
////////////////////////////////////////////////////////////////////

#include "cLerpInterval.h"
#include "string_utils.h"

TypeHandle CLerpInterval::_type_handle;

////////////////////////////////////////////////////////////////////
//     Function: CLerpInterval::string_blend_type
//       Access: Published, Static
//  Description: Returns the BlendType enumerated value corresponding
//               to the indicated string, or BT_invalid if the string
//               doesn't match anything.
////////////////////////////////////////////////////////////////////
CLerpInterval::BlendType CLerpInterval::
string_blend_type(const string &blend_type) {
  if (blend_type == "easeIn") {
    return BT_ease_in;
  } else if (blend_type == "easeOut") {
    return BT_ease_out;
  } else if (blend_type == "easeInOut") {
    return BT_ease_in_out;
  } else if (blend_type == "noBlend") {
    return BT_no_blend;
  } else {
    return BT_invalid;
  }
}

////////////////////////////////////////////////////////////////////
//     Function: CLerpInterval::compute_delta
//       Access: Protected
//  Description: Given a t value in the range [0, get_duration()],
//               returns the corresponding delta value clamped to the
//               range [0, 1], after scaling by duration and applying
//               the blend type.
////////////////////////////////////////////////////////////////////
double CLerpInterval::
compute_delta(double t) const {
  double duration = get_duration();
  if (duration == 0.0) {
    // If duration is 0, the lerp works as a set.  Thus, the delta is
    // always 1.0, the terminating value.
    return 1.0;
  }
  t /= duration;
  t = min(max(t, 0.0), 1.0);

  switch (_blend_type) {
  case BT_ease_in:
    {
      double t2 = t * t;
      return ((3.0 * t2) - (t2 * t)) * 0.5;
    }

  case BT_ease_out:
    {
      double t2 = t * t;
      return ((3.0 * t2) - (t2 * t)) * 0.5;
    }

  case BT_ease_in_out:
    {
      double t2 = t * t;
      return (3.0 * t2) - (2.0 * t * t2);
    }

  default:
    return t;
  }
}

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