cutes/vmath.h

#ifndef _fencer_vmath_h
#define _fencer_vmath_h

#include "stddef.h"
#include <math.h>

#if defined _WIN32 && ! defined isnanf
# define isnanf(x) _isnanf(x)
# define HAVE_ISNANF
#endif

#if VMATH_SDL == 1

#include <SDL2/SDL_rect.h>
typedef SDL_FPoint Vector;
typedef SDL_Point IVector;

#else

typedef struct Vector {
    float x;
    float y;
} Vector;

typedef struct IVector {
    int x;
    int y;
} IVector;

#endif

// Vector Constant Macros
#define ZeroVector (Vector){0.0f, 0.0f}
#define InfinityVector (Vector){INFINITY, INFINITY}
#define OneVector (Vector){1.0f,1.0f}

#define UpVector (Vector){0.0f,-1.0f}
#define RightVector (Vector){1.0f,0.0f}
#define LeftVector (Vector){-1.0f,0.0f}
#define DownVector (Vector){0.0f,1.0f}

#define MakeVector(__X, __Y) (Vector){__X, __Y}
#define VectorFrom(__A) (Vector){__A, __A}

// Integer Vector Constant Macros
#define ZeroIVector (IVector){0,0}
#define OneIVector (IVector){1,1}

#define UpIVector (IVector){-1,0}
#define DownIVector (IVector){1,0}
#define RightIVector (IVector){1,0}
#define LeftIVector (IVector){-1,0}

#define MakeIVector(__X, __Y) (IVector){__X, __Y}
#define IVectorFrom(__A) (IVector){__A, __A}

///
// Floating point vector maths functions.
///
static inline
int veqf(Vector a, Vector b) {
    const float e = 0.0001f;
    return fabsf(a.x - b.x) + fabsf(a.y - b.y) < e;
}
static inline
int visnanf(Vector a) {
    return isnanf(a.x) || isnanf(a.y);
}
static inline
Vector vaddf(Vector a, Vector b) {
    return (Vector){a.x + b.x, a.y + b.y};
}
static inline
Vector vsubf(Vector a, Vector b) {
    return (Vector){a.x - b.x, a.y - b.y};
}
static inline
Vector vmulff(Vector a, float b) {
    return (Vector){a.x * b, a.y * b};
}
static inline
Vector vmulf(Vector a, Vector b) {
    return (Vector) {a.x * b.x, a.y * b.y};
}
static inline
Vector vinvf(Vector a) {
    return (Vector){-a.x, -a.y};
}
static inline
Vector vperpendicularf(Vector a) {
    return (Vector){a.y, -a.x};
}
static inline
float vmagnitudef(Vector a) {
    if(veqf(a, ZeroVector)) return 0.f;
    a.x = fabsf(a.x);
    a.y = fabsf(a.y);
    return sqrtf(a.x*a.x + a.y*a.y);
}
static inline
float vsqrmagnitudef(Vector a) {
    a.x = fabsf(a.x);
    a.y = fabsf(a.y);
    return a.x*a.x + a.y*a.y;
}
static inline
Vector vnormalizedf(Vector a) {
    if(veqf(a, ZeroVector)) return ZeroVector;
    return vmulff(a, 1.0f/vmagnitudef(a));
}
static inline
float vdotf(Vector a, Vector b) {
    return (a.x*b.x) + (a.y*b.y);
}
static inline
float vdistancef(Vector a, Vector b) {
    return vmagnitudef(vsubf(a, b));
}
static inline
float vsqrdistf(Vector a, Vector b) {
    return vsqrmagnitudef(vsubf(a, b));
}
static inline
Vector vreciprocalf(Vector a) {
    return (Vector){1.0f/a.x, 1.0f/a.y};
}
static inline
Vector vrotatef(Vector a, float t) {
    return (Vector){
        cosf(t) * a.x - sinf(t) * a.y,
        sinf(t) * a.x + cosf(t) * a.y
    };
}
static inline
float vanglebetweenf(Vector a, Vector b) {
    return vdotf(a, b) / (vmagnitudef(a) * vmagnitudef(b));
}
static inline
Vector vprojectf(Vector onto, Vector from) {
    float dot = vdotf(onto, from);
    return vmulff(onto, dot);
}
static inline
Vector vlerpf(Vector start, Vector end, float t) {
    if(veqf(start, end))
        return end;
    t = fminf(fmaxf(0.0f, t), 1.0f);
    return vaddf(start, vmulff(vsubf(end, start), t));
}
static inline
Vector vmovetowardsf(Vector start, Vector end, float delta) {
    return vlerpf(start, end, delta / vdistancef(end, start));
}
static inline
Vector vaveragef(Vector* array, size_t count) {
    Vector acc = ZeroVector;
    for(size_t i = 0; i < count; ++i) {
        acc = vaddf(acc, array[i]);
    }
    return vmulff(acc, 1.0f/(float)count);
}

static inline
int veqi(IVector a, IVector b) {
    return a.x == b.x && a.y == b.y;
}

static inline
IVector vaddi(IVector a, IVector b) {
    return (IVector){a.x + b.x, a.y + b.y};
}
static inline
IVector vsubi(IVector a, IVector b) {
    return (IVector){a.x - b.x, a.y - b.y};
}
static inline
IVector vmuli(IVector a, IVector b) {
    return (IVector){a.x * b.x, a.y * b.y};
}

#endif // !_fencer_vmath_h