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float y = number; long i = *(long*) &y; i = 0x5f3759df - ( i >> 1 ); y = *(float*) &i; y = y * ( 1.5F - ( ( number * 0.5F ) * y * y ) );

float reciprocal_sqrt( float number ) { float y = number; long i = *(long*) &y; i = 0x5f3759df - ( i >> 1 ); y = *(float*) &i; y = y * ( 1.5F - ( ( number * 0.5F ) * y * y ) ); return y; }

#include <cmath> float reciprocal_sqrt( float number ) { return 1 / sqrt( number ); }

float reciprocal_sqrt( float number ) { float y = number; long i = *(long*) &y; i = 0x5f3759df - ( i >> 1 ); y = *(float*) &i; y = y * ( 1.5F - ( ( number * 0.5F ) * y * y ) ); return y; }

#include <cmath> float reciprocal_sqrt( float number ) { return 1 / sqrt( number ); }

/** * Calculate the reciprocal square root. * @param number The input number * @return The reciprocal square root of the input */ float reciprocal_square_root( float number ) { ... }

/** * Calculate the reciprocal square root. * @param number The input number * @return The reciprocal square root of the input */ float reciprocal_square_root( float number ) { ... }

/** * Calculate the reciprocal square root. * @param number The input number * @return The reciprocal square root of the input */ float reciprocal_square_root( float number ) { ... }

### What does the function do?

### What are the inputs?

### Why does this function exist?

### How do I use the function?

/** * Quickly calculate the reciprocal of the square root of * the given number. This is used instead of the * standard sqrt function for performance. Used by * [the vector2 class] to calculate magnitudes and unit * vectors. * * // Calculate the normalized vector of an input vector * vector2 input( 5, 6 ); * double len = pow(input.x, 2.0) + pow(input.y, 2.0); * double mag = rsqrt( len ); * vector2 normalized( input.x * mag, input.y * mag ); * * See https://en.wikipedia.org/wiki/Fast_inverse_square_root */ float reciprocal_square_root( float number ) { ... }