1 files changed, 180 insertions, 0 deletions
diff --git a/src/util/mini_math.h b/src/util/mini_math.h
new file mode 100644
index 0000000..1a87e0f
--- /dev/null
+++ b/src/util/mini_math.h
@@ -0,0 +1,180 @@
+// This file is part of the 64k demo project.
+// It provides shared vector, matrix and animation utilities, templatized and
+// inlined.
+
+#pragma once
+#include <cmath>
+
+// --- Configuration ---
+#define USE_VEC2
+#define USE_VEC3
+#define USE_VEC4
+#define USE_QUAT
+#define USE_MAT4
+#define USE_EASING
+#define USE_SPRING
+
+// --- Operator Macro ---
+// T: Class Name (e.g., vec3)
+// N: Number of active components for math (e.g., 3)
+#define VEC_OPERATORS(T, N) \
+    float& operator[](int i) { return v[i]; } \
+    const float& operator[](int i) const { return v[i]; } \
+    T& operator+=(const T& r) { for(int i=0; i<N; ++i) v[i]+=r.v[i]; return *this; } \
+    T& operator-=(const T& r) { for(int i=0; i<N; ++i) v[i]-=r.v[i]; return *this; } \
+    T& operator*=(float s)    { for(int i=0; i<N; ++i) v[i]*=s;      return *this; } \
+    T operator+(const T& r) const { T res(*this); res += r; return res; } \
+    T operator-(const T& r) const { T res(*this); res -= r; return res; } \
+    T operator*(float s)    const { T res(*this); res *= s; return res; } \
+    T operator-()           const { T res; for(int i=0; i<N; ++i) res.v[i] = -v[i]; return res; } \
+    static float dot(const T& a, const T& b) { float s=0; for(int i=0; i<N; ++i) s+=a.v[i]*b.v[i]; return s; } \
+    float dot(const T& a) const { return dot(*this, a); } \
+    float norm() const { return std::sqrt(dot(*this, *this)); } \
+    float len() const { return norm(); } \
+    float inv_norm() const { float l2 = dot(*this, *this); return l2 > 0 ? 1.0f/std::sqrt(l2) : 0; } \
+    T normalize() const { return (*this) * inv_norm(); }
+
+#ifdef USE_VEC2
+struct vec2 {
+    union { struct { float x, y; }; float v[2]; };
+    vec2(float x=0, float y=0) : x(x), y(y) {}
+    VEC_OPERATORS(vec2, 2)
+};
+#endif
+
+#ifdef USE_VEC3
+struct vec3 {
+    union { 
+        struct { float x, y, z; float _; }; // _ is padding for 16-byte alignment
+        float v[4]; // Size 4 to match alignment
+    };
+    vec3(float x=0, float y=0, float z=0) : x(x), y(y), z(z), _(0) {}
+    VEC_OPERATORS(vec3, 3) // Operators only touch x,y,z (indices 0,1,2)
+
+    static vec3 cross(vec3 a, vec3 b) { return {a.y*b.z-a.z*b.y, a.z*b.x-a.x*b.z, a.x*b.y-a.y*b.x}; }
+};
+#endif
+
+#ifdef USE_VEC4
+struct vec4 {
+    union { struct { float x, y, z, w; }; float v[4]; };
+    vec4(float x=0, float y=0, float z=0, float w=0) : x(x), y(y), z(z), w(w) {}
+    VEC_OPERATORS(vec4, 4)
+};
+#endif
+
+#ifdef USE_MAT4
+struct mat4 {
+    float m[16] = {1,0,0,0, 0,1,0,0, 0,0,1,0, 0,0,0,1}; // Identity (Column-Major)
+
+    static mat4 perspective(float fov, float asp, float n, float f) {
+        mat4 r = {}; float t = 1.0f/std::tan(fov*0.5f);
+        r.m[0]=t/asp; r.m[5]=t; r.m[10]=f/(n-f); r.m[11]=-1; r.m[14]=(n*f)/(n-f);
+        return r;
+    }
+
+    static mat4 look_at(vec3 eye, vec3 center, vec3 up) {
+        vec3 f = (center - eye).normalize();
+        vec3 s = vec3::cross(f, up).normalize();
+        vec3 u = vec3::cross(s, f);
+        mat4 res;
+        res.m[0] = s.x; res.m[4] = s.y; res.m[8] = s.z;
+        res.m[1] = u.x; res.m[5] = u.y; res.m[9] = u.z;
+        res.m[2] =-f.x; res.m[6] =-f.y; res.m[10]=-f.z;
+        res.m[12]=-vec3::dot(s, eye); res.m[13]=-vec3::dot(u, eye); res.m[14]= vec3::dot(f, eye);
+        return res;
+    }
+};
+#endif
+
+#ifdef USE_QUAT
+struct quat {
+    union { struct { float x, y, z, w; }; float v[4]; };
+    quat(float x=0, float y=0, float z=0, float w=1) : x(x), y(y), z(z), w(w) {}
+    VEC_OPERATORS(quat, 4)
+
+    quat operator*(const quat& q) const {
+        return { w*q.x + x*q.w + y*q.z - z*q.y, w*q.y - x*q.z + y*q.w + z*q.x,
+                 w*q.z + x*q.y - y*q.x + z*q.w, w*q.w - x*q.x - y*q.y - z*q.z };
+    }
+
+    static quat from_axis(vec3 a, float ang) {
+        float s = std::sin(ang*0.5f); return {a.x*s, a.y*s, a.z*s, std::cos(ang*0.5f)};
+    }
+
+    static quat from_to(vec3 a, vec3 b) {
+        float d = vec3::dot(a, b); vec3 axis = vec3::cross(a, b);
+        if (d < -0.9999f) return {0, 1, 0, 0};
+        float s = std::sqrt((1.0f + d) * 2.0f), inv_s = 1.0f/s;
+        return {axis.x*inv_s, axis.y*inv_s, axis.z*inv_s, s*0.5f};
+    }
+
+    static quat look_at(vec3 eye, vec3 target, vec3 up) {
+        vec3 f = (target - eye).normalize();
+        vec3 r = vec3::cross(f, up).normalize();
+        vec3 u = vec3::cross(r, f);
+        float m00 = r.x, m11 = u.y, m22 = -f.z, tr = m00 + m11 + m22;
+        if (tr > 0) {
+            float s = std::sqrt(tr + 1.0f) * 2.0f;
+            return { (u.z - (-f.y)) / s, ((-f.x) - r.z) / s, (r.y - u.x) / s, 0.25f * s };
+        } else if ((m00 > m11) && (m00 > m22)) {
+            float s = std::sqrt(1.0f + m00 - m11 - m22) * 2.0f;
+            return { 0.25f * s, (r.y + u.x) / s, ((-f.x) + r.z) / s, (u.z - (-f.y)) / s };
+        } else if (m11 > m22) {
+            float s = std::sqrt(1.0f + m11 - m00 - m22) * 2.0f;
+            return { (r.y + u.x) / s, 0.25f * s, (u.z + (-f.y)) / s, ((-f.x) - r.z) / s };
+        } else {
+            float s = std::sqrt(1.0f + m22 - m00 - m11) * 2.0f;
+            return { ((-f.x) + r.z) / s, (u.z + (-f.y)) / s, 0.25f * s, (r.y - u.x) / s };
+        }
+    }
+
+    vec3 rotate(vec3 v_in) const {
+        vec3 qv(x, y, z), t = vec3::cross(qv, v_in) * 2.0f;
+        return v_in + t * w + vec3::cross(qv, t);
+    }
+
+    mat4 to_mat() const {
+        mat4 r; float x2=x+x, y2=y+y, z2=z+z, xx=x*x2, xy=x*y2, xz=x*z2, yy=y*y2, yz=y*z2, zz=z*z2, wx=w*x2, wy=w*y2, wz=w*z2;
+        r.m[0]=1-(yy+zz); r.m[4]=xy-wz; r.m[8]=xz+wy; r.m[1]=xy+wz; r.m[5]=1-(xx+zz); r.m[9]=yz-wx; r.m[2]=xz-wy; r.m[6]=yz+wx; r.m[10]=1-(xx+yy);
+        return r;
+    }
+};
+
+inline quat slerp(quat a, quat b, float t) {
+    float d = a.x*b.x + a.y*b.y + a.z*b.z + a.w*b.w;
+    if (d < 0) { b = b * -1.0f; d = -d; }
+    if (d > 0.9995f) { // Linear fall-back
+        quat r; for(int i=0;i<4;++i) r.v[i] = a.v[i] + (b.v[i] - a.v[i])*t; 
+        return r; 
+    }
+    float th0 = std::acos(d), th = th0*t, s0 = std::sin(th0), s1 = std::sin(th)/s0, s2 = std::sin(th0-th)/s0;
+    return a * s2 + b * s1;
+}
+#endif
+
+template<typename T>
+inline T lerp(const T& a, const T& b, float t) { return a + (b - a) * t; }
+
+#ifdef USE_EASING
+namespace ease {
+    inline float out_cubic(float t) { return 1.0f - std::pow(1.0f - t, 3.0f); }
+    inline float in_out_quad(float t) { return t < 0.5f ? 2.0f*t*t : 1.0f - std::pow(-2.0f*t + 2.0f, 2.0f) / 2.0f; }
+    inline float out_expo(float t) { return t == 1.0f ? 1.0f : 1.0f - std::pow(2.0f, -10.0f * t); }
+}
+#endif
+
+#ifdef USE_SPRING
+namespace spring {
+    template<typename T>
+    void solve(T& current, T& velocity, const T& target, float smooth_time, float dt) {
+        float omega = 2.0f / smooth_time;
+        float x = omega * dt;
+        float exp = 1.0f / (1.0f + x + 0.48f*x*x + 0.235f*x*x*x);
+        T change = current - target;
+        T temp = (velocity + change * omega) * dt;
+        velocity = (velocity - temp * omega) * exp;
+        current = target + (change + temp) * exp;
+    }
+}
+#endif