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#pragma once
#include "defs.h"
#include <assert.h>
#include <stdbool.h>
/// A 3D vector.
typedef struct vec3 {
R x, y, z;
} vec3;
/// Construct a vector from 3 coordinates.
static inline vec3 vec3_make(R x, R y, R z) { return (vec3){x, y, z}; }
/// Construct a vector from an array.
static inline vec3 vec3_from_array(const R xyz[3]) {
return (vec3){xyz[0], xyz[1], xyz[2]};
}
/// Construct a vector from a single scalar value.
/// x = y = z = val.
static inline vec3 vec3_from_scalar(R val) { return (vec3){val, val, val}; }
/// Return the vector's ith coordinate.
static inline R vec3_ith(vec3 v, int i) {
assert(i >= 0 && i < 3);
return ((const R*)&v)[i];
}
/// Negate the given vector.
static inline vec3 vec3_neg(vec3 v) { return (vec3){-v.x, -v.y, -v.z}; }
/// Add two vectors.
static inline vec3 vec3_add(vec3 a, vec3 b) {
return (vec3){a.x + b.x, a.y + b.y, a.z + b.z};
}
/// Subtract two vectors.
static inline vec3 vec3_sub(vec3 a, vec3 b) {
return (vec3){a.x - b.x, a.y - b.y, a.z - b.z};
}
/// Modulate two vectors (component-wise multiplication).
static inline vec3 vec3_mul(vec3 a, vec3 b) {
return (vec3){a.x * b.x, a.y * b.y, a.z * b.z};
}
/// Divide two vectors component-wise.
static inline vec3 vec3_div(vec3 a, vec3 b) {
return (vec3){a.x / b.x, a.y / b.y, a.z / b.z};
}
/// Scale a vector by a scalar value.
static inline vec3 vec3_scale(vec3 v, R s) {
return (vec3){v.x * s, v.y * s, v.z * s};
}
/// Compare two vectors for equality.
static inline bool vec3_eq(vec3 a, vec3 b) {
return a.x == b.x && a.y == b.y && a.z == b.z;
}
/// Return the absolute value of the vector.
static inline vec3 vec3_abs(vec3 v) {
return (vec3){rabs(v.x), rabs(v.y), rabs(v.z)};
}
/// Compare two vectors for inequality.
static inline bool vec3_ne(vec3 a, vec3 b) { return !(vec3_eq(a, b)); }
/// Return the vector's squared magnitude.
static inline R vec3_norm2(vec3 v) { return v.x * v.x + v.y * v.y + v.z * v.z; }
/// Return the vector's magnitude.
static inline R vec3_norm(vec3 v) { return sqrt(vec3_norm2(v)); }
/// Return the squared distance between two points.
static inline R vec3_dist2(vec3 a, vec3 b) {
const vec3 v = vec3_sub(b, a);
return vec3_norm2(v);
}
/// Return the distance between two points.
static inline R vec3_dist(vec3 a, vec3 b) { return sqrt(vec3_dist2(a, b)); }
/// Return the given vector divided by its magnitude.
static inline vec3 vec3_normalize(vec3 v) {
const R n = vec3_norm(v);
assert(n > 0);
return (vec3){v.x / n, v.y / n, v.z / n};
}
/// Return the dot product of two vectors.
static inline R vec3_dot(vec3 a, vec3 b) {
return a.x * b.x + a.y * b.y + a.z * b.z;
}
/// Return the cross product of two vectors.
static inline vec3 vec3_cross(vec3 a, vec3 b) {
return (vec3){
a.y * b.z - a.z * b.y, a.z * b.x - a.x * b.z, a.x * b.y - a.y * b.x};
}
/// Reflect the vector about the normal.
static inline vec3 vec3_reflect(vec3 v, vec3 n) {
// r = v - 2 * dot(v, n) * n
return vec3_sub(v, vec3_scale(n, 2 * vec3_dot(v, n)));
}
/// Refract the vector about the normal.
static inline vec3 vec3_refract(vec3 v, vec3 n, R e) {
// k = 1 - e^2(1 - dot(n,v) * dot(n,v))
const R k = 1.0 - e * e * (1.0 - vec3_dot(n, v) * vec3_dot(n, v));
assert(k >= 0);
// r = e*v - (e * dot(n,v) + sqrt(k)) * n
return vec3_sub(
vec3_scale(v, e), vec3_scale(n, e * vec3_dot(n, v) * sqrt(k)));
}
/// Elevate the vector to a power.
static inline vec3 vec3_pow(vec3 v, R p) {
return (vec3){pow(v.x, p), pow(v.y, p), pow(v.z, p)};
}
/// The (1, 0, 0) vector.
static inline vec3 right3() { return (vec3){1.0, 0.0, 0.0}; }
/// The (0, 1, 0) vector.
static inline vec3 up3() { return (const vec3){0.0, 1.0, 0.0}; }
/// The (0, 0, -1) vector.
static inline vec3 forward3() { return (const vec3){0.0, 0.0, -1.0}; }
/// The (0, 0, 0) vector.
static inline vec3 zero3() { return (const vec3){0.0, 0.0, 0.0}; }
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