GLM math constants

[Scotopik]

Hi,

I'm new to GLM (what an awesome library btw), and can't find any math constants, which seems odd given its functional coverage.

Specifically I'm looking for just good old M_PI. I see hardwired constants all over the place, which again seems odd to me. For instance in glm::core::function::trigonometric the 'degrees' function (and all other associated trigonometric functions) defines pi in place (3.141...), like this:

// radians
template <typename genType>
GLM_FUNC_QUALIFIER genType radians
(
    genType const & degrees
)
{
    GLM_STATIC_ASSERT(detail::type<genType>::is_float, "'radians' only accept floating-point input");
 
    const genType pi = genType(3.1415926535897932384626433832795);
    return degrees * (pi / genType(180));
}

Can anyone lead me in the right direction?

Cheers,
Shane

[Groovounet]

That's a good point, there is no constant provided by GLM.

Which constant would be useful for you?

[ZbuffeR]

Wouldn't the ones in math.h be useful ?

[Alfonse Reinheart]

Useful but redundant since they're already in math.h.

Now, M_PI is not part of math.h anymore thanks to C99. So it's reasonable to define that. Though if they're using C++, then C++ standard library still includes it (I think) as part of its math.h. So you may want to check to see if it is defined first.

[Scotopik]

Well usually M_PI (and crew) are defined in math.h as:

#define M_E         2.71828182845904523536028747135266250   /* e */
#define M_LOG2E     1.44269504088896340735992468100189214   /* log 2e */
#define M_LOG10E    0.434294481903251827651128918916605082  /* log 10e */
#define M_LN2       0.693147180559945309417232121458176568  /* log e2 */
#define M_LN10      2.30258509299404568401799145468436421   /* log e10 */
#define M_PI        3.14159265358979323846264338327950288   /* pi */
#define M_PI_2      1.57079632679489661923132169163975144   /* pi/2 */
#define M_PI_4      0.785398163397448309615660845819875721  /* pi/4 */
#define M_1_PI      0.318309886183790671537767526745028724  /* 1/pi */
#define M_2_PI      0.636619772367581343075535053490057448  /* 2/pi */
#define M_2_SQRTPI  1.12837916709551257389615890312154517   /* 2/sqrt(pi) */
#define M_SQRT2     1.41421356237309504880168872420969808   /* sqrt(2) */
#define M_SQRT1_2   0.707106781186547524400844362104849039  /* 1/sqrt(2) */

However, so are many of the standard trigonometric functions:

extern double  acos( double );
extern double  asin( double );
extern double  atan( double );
extern double  atan2( double, double );
extern double  cos( double );
extern double  sin( double );
extern double  tan( double );
extern double  acosh( double );
extern double  asinh( double );
extern double  atanh( double );
extern double  cosh( double );
extern double  sinh( double );
extern double  tanh( double );

However, these trigonometric functions are redefined in GLM in func_trigonometric.inl, despite the fact they call the std functions. For instance, 'sin':

    // sin
    template <typename genType>
    GLM_FUNC_QUALIFIER genType sin
	(
		genType const & angle
	)
    {
		GLM_STATIC_ASSERT(detail::type<genType>::is_float, "'sin' only accept floating-point input");
 
		return ::std::sin(angle);
    }

I guess the idea is that GLM is supposed to be a one-stop-shop for math, which is great and absolutely needed, so why not go the whole way and move over the standard constants too.

I would expect to see something like, glm::M_PI or glm::constants:i .

Basically, I would love to more or less replace <math> and <math.h> with <gml.h> and be done with it.

Cheers,
Shane

[Alfonse Reinheart]

I guess the idea is that GLM is supposed to be a one-stop-shop for math

I'm fairly sure the idea is to do what GLSL does. GLSL has a function called "sin" which can take a scalar float (as well as vectors). Therefore, GLM must have a function called "sin" which takes a scalar float.

[Groovounet]

I have added a ticket for this:
https://sourceforge.net/apps/trac/ogl-math/ticket/94

I am not sure how this could be exposed but it could be interesting.

[Scotopik]

Excellent.

Thanks and fingers crossed we find some constants in GLM soonish.

Cheers,
Shane

[Scotopik]

True, however given PI is a fundamental mathematical constant, and used in graphics programming all the time (at least by me, but I use radians in my math), it struck me as odd that it was absent.

[liquid11111]

What now, can I found some constants in GLM?
ticket link does not working