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// calculate the length of the hypotenuse of a right-angle triangle
float hypot( in float x, in float y )
{
// (sqrt( x * x + y * y )) might over- or underflow
// see http://en.wikipedia.org/wiki/Hypot for details
x = abs( x );
y = abs( y );
float t = min( x, y );
x = max( x, y );
t = t/x;
return( x * sqrt( 1.0f + ( t * t ) ) );
}
float gradientGetPosition( in int gradientMode, in vec2 xy )
{
// clamp to [0,1]
vec2 tex = xy - floor( xy );
switch( gradientMode )
{
case gradient_linear :
return( tex.x );
case gradient_squared :
return( tex.x * tex.x );
case gradient_box :
// gradient is based on the distance from the center
return( max( abs( tex.x - 0.5f ), abs( tex.y - 0.5f ) ) );
case gradient_diagonal :
// gradient is based on the distance from the diagonal
return( sqrt(2.0f) * abs( tex.x - tex.y ) );
case gradient_90_degree :
// Need to check
return( 0.0f );
case gradient_symmetric_90_degree :
// Need to check
return( 0.0f );
case gradient_radial :
// Distance from center
return( 2.0f * hypot( tex.x - 0.5f, tex.y - 0.5f ) );
case gradient_360_degree :
// fall through need to check
default :
return( 0.0f );
}
}
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