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stBasicTerrain.I
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1/**
2 * PANDA 3D SOFTWARE
3 * Copyright (c) Carnegie Mellon University. All rights reserved.
4 *
5 * All use of this software is subject to the terms of the revised BSD
6 * license. You should have received a copy of this license along
7 * with this source code in a file named "LICENSE."
8 *
9 * @file stBasicTerrain.I
10 * @author drose
11 * @date 2010-10-12
12 */
13
14/**
15 * Specifies the image filename that will define the height map of the
16 * terrain. This will require a subsequent call to load_data() to actually
17 * read the data.
18 */
19INLINE void STBasicTerrain::
20 set_height_map(const Filename &height_map) {
21 _height_map = height_map;
22 _is_valid = false;
23}
24
25/**
26 * Returns the image filename that defines the height map of the terrain.
27 */
28INLINE const Filename &STBasicTerrain::
29 get_height_map() const {
30 return _height_map;
31}
32
33/**
34 * Returns the length, in scene graph units, of one edge of the heightmap as
35 * it is manifested by the terrain. Increasing this number spreads the
36 * heightmap out over a greater area.
37 */
38INLINE PN_stdfloat STBasicTerrain::
39 get_size() const {
40 return _size;
41}
42
43/**
44 * Convenience function to calculate the linear interpolation from A to B.
45 */
46INLINE PN_stdfloat STBasicTerrain::
47interpolate(PN_stdfloat a, PN_stdfloat b, PN_stdfloat t) {
48 return (a + (b - a) * t);
49}
50
51/**
52 *
53 */
54 template<class ValueType>
55STBasicTerrain::InterpolationData<ValueType>::
56InterpolationData() : _width(0), _height(0)
57{
58}
59
60/**
61 * Resets the array to an empty array of width x height cells.
62 */
63 template<class ValueType>
64 void STBasicTerrain::InterpolationData<ValueType>::
65reset(int width, int height) {
66 _width = width;
67 _height = height;
68 _data.clear();
69 _data.insert(_data.begin(), width * height, ValueType());
70}
71
72/**
73 * Returns the value nearest to (u, v) in the data.
74 */
75 template<class ValueType>
76 ValueType STBasicTerrain::InterpolationData<ValueType>::
77get_nearest_neighbor(PN_stdfloat u, PN_stdfloat v) const {
78 int u = int(u * _width + 0.5f);
79 int v = int(v * _height + 0.5f);
80 int index = u + v * _width;
81 nassertr(index >= 0 && index < (int)_data.size(), 0);
82 return _data[index];
83}
84
85/**
86 * Interpolates the value at (u, v) between its four nearest neighbors.
87 */
88 template<class ValueType>
89 ValueType STBasicTerrain::InterpolationData<ValueType>::
90calc_bilinear_interpolation(PN_stdfloat u, PN_stdfloat v) const {
91 u -= cfloor(u);
92 v -= cfloor(v);
93
94 u *= (PN_stdfloat)_width;
95 v *= (PN_stdfloat)_height;
96
97 const int lower_x = int(u);
98 const int lower_y = int(v);
99 const int higher_x = (lower_x + 1) % _width;
100 const int higher_y = (lower_y + 1) % _height;
101
102 const PN_stdfloat ratio_x = u - PN_stdfloat(lower_x);
103 const PN_stdfloat ratio_y = v - PN_stdfloat(lower_y);
104 const PN_stdfloat inv_ratio_x = 1.0f - ratio_x;
105 const PN_stdfloat inv_ratio_y = 1.0f - ratio_y;
106
107 nassertr(lower_x + lower_y * _width >= 0 && higher_x + higher_y * _width < (int)_data.size(), 0);
108
109 const ValueType &t1 = _data[lower_x + lower_y * _width];
110 const ValueType &t2 = _data[higher_x + lower_y * _width];
111 const ValueType &t3 = _data[lower_x + higher_y * _width];
112 const ValueType &t4 = _data[higher_x + higher_y * _width];
113
114 return (t1 * inv_ratio_x + t2 * ratio_x) * inv_ratio_y +
115 (t3 * inv_ratio_x + t4 * ratio_x) * ratio_y;
116}
117
118/**
119 * Approximates the average value at (u, v) over the indicated radius,
120 * assuming a polynomial curve.
121 */
122 template<class ValueType>
123 ValueType STBasicTerrain::InterpolationData<ValueType>::
124calc_smooth(PN_stdfloat u, PN_stdfloat v, PN_stdfloat radius) const {
125 ValueType retval = 0;
126
127 if (radius <= 0.0f) {
128 retval = calc_bilinear_interpolation(u, v);
129
130 } else {
131 const PN_stdfloat test_points[9][2] = {
132 { 0.0f * radius, 0.0f * radius },
133 { 0.8f * radius, 0.0f * radius },
134 { -0.8f * radius, 0.0f * radius },
135 { 0.0f * radius, 0.8f * radius },
136 { 0.0f * radius, -0.8f * radius },
137 { 0.25f * radius, 0.25f * radius },
138 { 0.25f * radius, -0.25f * radius },
139 { -0.25f * radius, 0.25f * radius },
140 { -0.25f * radius, -0.25f * radius }
141 };
142
143 PN_stdfloat total_weight = 0.0f;
144 for (int i = 0; i < 9; ++i) {
145 const PN_stdfloat *test_point = test_points[i];
146 PN_stdfloat weight = (1.0f - sqrt((test_point[0] * test_point[0]) + (test_point[1] * test_point[1])));
147 total_weight += weight;
148 retval += weight * calc_bilinear_interpolation(u + test_point[0], v + test_point[1]);
149 }
150
151 retval /= total_weight;
152 }
153
154 return retval;
155}
156
157/**
158 * Returns true if the data is present--that is, reset() was called with non-
159 * zero values--or false otherwise.
160 */
161 template<class ValueType>
162 bool STBasicTerrain::InterpolationData<ValueType>::
163is_present() const {
164 return !_data.empty();
165}
ValueType
Filename
The name of a file, such as a texture file or an Egg file.
Definition filename.h:44
STBasicTerrain::get_size
PN_stdfloat get_size() const
Returns the length, in scene graph units, of one edge of the heightmap as it is manifested by the ter...
Definition stBasicTerrain.I:39
STBasicTerrain::set_height_map
void set_height_map(const Filename &height_map)
Specifies the image filename that will define the height map of the terrain.
Definition stBasicTerrain.I:20
STBasicTerrain::get_height_map
const Filename & get_height_map() const
Returns the image filename that defines the height map of the terrain.
Definition stBasicTerrain.I:29