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(svn r13667) -Documentation: Comment 'tgp.cpp' a bit. Based on patch by CommanderZ.

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frosch 2008-06-30 19:54:03 +00:00
parent ac3896feaf
commit e9e453cf8b
1 changed files with 42 additions and 6 deletions
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48
src/tgp.cpp
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@ -174,6 +174,12 @@ struct HeightMap
uint size_x; //< MapSizeX()
uint size_y; //< MapSizeY()
/**
* Height map accessor
* @param x X position
* @param y Y position
* @return height as fixed point number
*/
inline height_t &height(uint x, uint y) {
return h[x + y * dim_x];
}
@ -234,7 +240,10 @@ static inline bool IsValidXY(uint x, uint y)
}
/** Allocate array of (MapSizeX()+1)*(MapSizeY()+1) heights and init the _height_map structure members */
/**
* Allocate array of (MapSizeX()+1)*(MapSizeY()+1) heights and init the _height_map structure members
* @return true on success
*/
static inline bool AllocHeightMap()
{
height_t *h;
@ -262,7 +271,11 @@ static inline void FreeHeightMap()
_height_map.h = NULL;
}
/** RandomHeight() generator */
/**
* Generates new random height in given amplitude (generated numbers will range from - amplitude to + amplitude)
* @param rMax Limit of result
* @return generated height
*/
static inline height_t RandomHeight(amplitude_t rMax)
{
amplitude_t ra = (Random() << 16) | (Random() & 0x0000FFFF);
@ -272,13 +285,31 @@ static inline height_t RandomHeight(amplitude_t rMax)
return rh;
}
/** One interpolation and noise round */
/**
* One interpolation and noise round
*
* The heights on the map are generated in an iterative process.
* We start off with a frequency of 1 (log_frequency == 0), and generate heights only for corners on the most coarsly mesh
* (i.e. only for x/y coordinates which are multiples of the minimum edge length).
*
* After this initial step the frequency is doubled (log_frequency incremented) each iteration to generate corners on the next finer mesh.
* The heights of the newly added corners are first set by interpolating the heights from the previous iteration.
* Finally noise with the given amplitude is applied to all corners of the new mesh.
*
* Generation terminates, when the frequency has reached the map size. I.e. the mesh is as fine as the map, and every corner height
* has been set.
*
* @param log_frequency frequency (logarithmic) to apply noise for
* @param amplitude Amplitude for the noise
* @return false if we are finished (reached the minimal step size / highest frequency)
*/
static bool ApplyNoise(uint log_frequency, amplitude_t amplitude)
{
uint size_min = min(_height_map.size_x, _height_map.size_y);
uint step = size_min >> log_frequency;
uint x, y;
/* Trying to apply noise to uninitialized height map */
assert(_height_map.h != NULL);
/* Are we finished? */
@ -316,11 +347,13 @@ static bool ApplyNoise(uint log_frequency, amplitude_t amplitude)
}
}
/* Add noise for next higher frequency (smaller steps) */
for (y = 0; y <= _height_map.size_y; y += step) {
for (x = 0; x <= _height_map.size_x; x += step) {
_height_map.height(x, y) += RandomHeight(amplitude);
}
}
return (step > 1);
}
@ -338,16 +371,19 @@ static void HeightMapGenerate()
for (log_size_min = 6; (1U << log_size_min) < size_min; log_size_min++) { }
log_frequency_min = log_size_min - 6;
/* Keep increasing the frequency until we reach the step size equal to one tile */
do {
log_frequency = iteration_round - log_frequency_min;
if (log_frequency >= 0) {
/* Apply noise for the next frequency */
amplitude = _amplitudes_by_smoothness_and_frequency[_settings_game.game_creation.tgen_smoothness][log_frequency];
} else {
/* Amplitude for the low frequencies on big maps is 0, i.e. initialise with zero height */
amplitude = 0;
}
continue_iteration = ApplyNoise(iteration_round, amplitude);
iteration_round++;
} while(continue_iteration);
} while (continue_iteration);
}
/** Returns min, max and average height from height map */
@ -379,7 +415,7 @@ static int *HeightMapMakeHistogram(height_t h_min, height_t h_max, int *hist_buf
int *hist = hist_buf - h_min;
height_t *h;
/* Fill histogram */
/* Count the heights and fill the histogram */
FOR_ALL_TILES_IN_HEIGHT(h) {
assert(*h >= h_min);
assert(*h <= h_max);
@ -769,7 +805,7 @@ static double perlin_coast_noise_2D(const double x, const double y, const double
}
/** A small helper function */
/** A small helper function to initialize the terrain */
static void TgenSetTileHeight(TileIndex tile, int height)
{
SetTileHeight(tile, height);