blmath.h File Reference

#include <stdbool.h>

Go to the source code of this file.

Macros
#define	PI   3.1415926535897932384626433832795028841971693993751
#define	PI_2   1.5707963267948966192313216916397514420985846996876
#define	SQRT2   1.4142135623730950488016887242096980785696718753769

Functions
double	bl_difference (double a, double b)
double	bl_norm (double value, double min, double max)
double	bl_lerp (double t, double min, double max)
double	bl_map (double src_value, double src_min, double src_max, double dst_min, double dst_max)
double	bl_wrap (double value, double min, double max)
double	bl_clamp (double value, double min, double max)
double	bl_round_to (double value, int decimals)
double	bl_round_to_nearest (double value, double mult)
double	bl_sin_range (double angle, double min, double max)
double	bl_cos_range (double angle, double min, double max)
double	bl_fract (double value)
double	bl_lerp_sin (double value, double min, double max)
bool	bl_equalish (double a, double b, double delta)

Macro Definition Documentation

PI

#define PI   3.1415926535897932384626433832795028841971693993751

PI_2

#define PI_2   1.5707963267948966192313216916397514420985846996876

SQRT2

#define SQRT2   1.4142135623730950488016887242096980785696718753769

Function Documentation

bl_clamp()

double bl_clamp	(	double	value,
		double	min,
		double	max
	)

Clamps a value within a range.

If the value is lower then the minimum value of the range, bl_clamp will return the minimum value. If the value is higher than the maximum, it will return the maximum.

Parameters

double	value The input value.
double	min The minimum of the range.
double	max The maximum of the range.

Returns

double.

bl_cos_range()

double bl_cos_range	(	double	angle,
		double	min,
		double	max
	)

Given an angle, returns a number between min and max.

Given a series of angles from 0 to 2PI, bl_cos_range will return values conforming a cosine wave, starting at max, going down to (max+min)/2, then to min, back to the average of the two and then max.

Parameters

double	angle The input angle.
double	min The minumum of the sine wave.
double	max The maximum of the sine wave.

Returns

double

Examples

bl_cos_range(0, -10, 10) // returns 10 (max)
bl_cos_range(PI / 2, -10, 10) // returns 0 (min+max) / 2
bl_cos_range(PI, -10, 10) // returns -10 (min)

bl_difference()

double bl_difference	(	double	a,
		double	b
	)

Returns the absolute value of the difference between two numbers.

Subtracting two different numbers may give you a negative number. This just takes the absolute value of that result.

Parameters

double	a One number.
double	b The other number.

Returns

double

Examples

bl_difference(1, 3) // returns 2
// |1 - 2| = 2

bl_equalish()

bool bl_equalish	(	double	a,
		double	b,
		double	delta
	)

Returns a bool representing whether or not two double values are equal to within a certain range.

Parameters

double	a One number.
double	b Another number.
double	delta How close the numbers should be to be considered equal.

Examples

bl_equalish(1, 1.0001, 0.001)   // returns true
bl_equalish(1, 1.0001, 0.00001) // returns false

bl_fract()

double bl_fract

(

double

value

)

Returns the fractional part of a floating point number.

You could use the built-in double modf(double x, double *integer) function if you want both the fractional and integer part of a number.

Parameters

double

value The input value.

Returns

double

Examples

bl_fract(1.23) // returns 0.23

bl_lerp()

double bl_lerp	(	double	t,
		double	min,
		double	max
	)

Linear interpolation within a range.

If the interpolation value (t) is 0, bl_lerp will return min. If t is 1, it will return max. For t values between 0 and 1, bl_lerp will interpolate between min and max.

This also suppots t values below 0 and above 1, in which case the return will be outside the min/max range.

Parameters

double	t The interpolation value.
double	min The minimum of the range.
double	max The maximum of the range.

Returns

double

Examples

bl_lerp(0.5, 20, 40) // returns 30
// 30 is 50% of the way between 20 and 40

bl_lerp_sin()

double bl_lerp_sin	(	double	value,
		double	min,
		double	max
	)

Interpolates a normalized input value (0 to 1) to a sine wave extending from min to max.

This function is equivalent to calling bl_sin_range(value * PI * 2, min, max). If you have an input value which can be treated as an angle, use bl_sin_range. If you have a normalized value, use this.

Parameters

double	value The input value.
double	min The minimum of the sine wave.
double	max The maximum of the sine wave.

Returns

double

Examples

bl_lerp_sin(0.25, -10, 10) // returns 10 (max)

bl_map()

double bl_map	(	double	src_value,
		double	src_min,
		double	src_max,
		double	dst_min,
		double	dst_max
	)

Maps a value within one range to a corresponding value within a different range.

Essentialy, the applies a norm function on src_value, src_min, and src_max. Then uses the result of that as an input to a lerp function with dst_min and dst_max.

Parameters

double	src_value The source value within the source range.
double	src_min The minimum of the source range.
double	src_max The maximum of the source range.
double	dst_min The minimum of the destination range.
double	dst_max The maximum of the destination range.

Returns

double

Examples

bl_map(40, 30, 50, 0, 1000) // returns 500
// 40 is 50% of the way between 30 and 50
// 500 is 50% of the way between 0 and 1000

bl_norm()

double bl_norm	(	double	value,
		double	min,
		double	max
	)

Returns the normalized value of a number within a min/max range.

If the input value is the same as the minimum, bl_norm will return 0. If it is the same as the maximum value, it will return 1. If it is between min and max, it will return a number between 0 and 1.

This also supports input values below min (will return a negative number) and above max (will return a number greater than 1).

Parameters

double	value The number to normalize.
double	min. The minimum of the range.
double	max. The maximum of the range.

Returns

double

Examples

bl_norm(80, 50, 100) // returns 0.6
// 80 is 60% of the way between 50 and 100

bl_round_to()

double bl_round_to	(	double	value,
		int	decimals
	)

Rounds a value to a power of 10 (positive or negative).

If the decimals value is 0, this acts the same as a simple round. If decimals is positive, it will round to the nearest multiple of 10, 100, 1000, etc. If decimals is negative, it will round to the nearest 0.1, 0.01, 0.001, etc.

Parameters

double	value The input value.
double	value How many decimals to round to.

Returns

double

Examples

bl_round_to(1234, 2) // returns 1200
bl_round_to(1234.5678, -2) // returns 1234.57

bl_round_to_nearest()

double bl_round_to_nearest	(	double	value,
		double	mult
	)

Returns a value rounded to the nearest multiple of another number.

Setting mult to 10 has the same effect as bl_round_to.

You can set mult to a fraction to round to the nearest multiple of that fraction.

Parameters

double	value The input value.
mult	The multiple to round to.

Returns

double

Examples

bl_round_to_nearest(23, 8) // returns 24
bl_round_to_nearest(5.7123, 0.25) // returns 5.75

bl_sin_range()

double bl_sin_range	(	double	angle,
		double	min,
		double	max
	)

Given an angle, returns a number between min and max.

Given a series of angles from 0 to 2PI, bl_sin_range will return values conforming a sine wave, starting at (max+min)/2, rising to max, going back to min, and back to the average of the two.

Parameters

double	angle The input angle.
double	min The minumum of the sine wave.
double	max The maximum of the sine wave.

Returns

double

Examples

bl_sin_range(0, -10, 10) // returns 0 (-10 + 10) / 2
bl_sin_range(PI / 2, -10, 10) // returns 10 (max)
bl_sin_range(PI * 2 / 3, -10, 10) // returns -10 (min)

bl_wrap()

double bl_wrap	(	double	value,
		double	min,
		double	max
	)

Returns the input value if it is within a range, or wraps it around the range if not.

If the input value goes to or beyond the max value, it will wrap around and start counting from min. If the input value is less than min, it will wrap around and start counting backwards from max.

Note that this is basically an advanced form of modulo. If the input value is exactly equal to max, wrap will return min. Calling wrap with 0 as min acts exactly the same as module.

An instance where you might use this is in constraining hues to a particular range of the spectrum. Or animating an object that you want to leave one side of the screen and return on the opposite side.

Parameters

double	value The input value.
double	min The minimum of the range.
double	max The maximum of the range.

Returns

double

Examples

bl_wrap(5, 3, 8) // returns 5. 5 is within the range.

bl_wrap(8, 3, 8) // returns 3. 8 has hit the max and wraps.

bl_wrap(10, 3, 8) // returns 5. 10 is 2 beyond max, so it returns min + 2

bl_wrap(1, 3, 8)  // returns 6. 1 is 2 less than min, it returns max - 2