usually works. need to figure out what causes it to not to sometimes.

util/vecmat/mat4.hpp

@@ -321,4 +321,37 @@ using Mat4f = Mat4<float>;
 using Mat4d = Mat4<double>;
 
 
+Mat4f lookAt(const Vec3f& eye, const Vec3f& center, const Vec3f& up) {
+    Vec3f const f = (center - eye).normalized();
+    Vec3f const s = f.cross(up).normalized();
+    Vec3f const u = s.cross(f);
+
+    Mat4f Result = Mat4f::identity();
+    Result(0, 0) = s.x;
+    Result(1, 0) = s.y;
+    Result(2, 0) = s.z;
+    Result(3, 0) = -s.dot(eye);
+    Result(0, 1) = u.x;
+    Result(1, 1) = u.y;
+    Result(2, 1) = u.z;
+    Result(3, 1) = -u.dot(eye);
+    Result(0, 2) = -f.x;
+    Result(1, 2) = -f.y;
+    Result(2, 2) = -f.z;
+    Result(3, 2) = f.dot(eye);
+    return Result;
+}
+
+Mat4f perspective(float fovy, float aspect, float zNear, float zfar) {
+    float const tanhalfF = tan(fovy / 2);
+    Mat4f Result = 0;
+    Result(0,0) = 1 / (aspect * tanhalfF);
+    Result(1,1) = 1 / tanhalfF;
+    Result(2,2) = zfar / (zNear - zfar);
+    Result(2,3) = -1;
+    Result(3,2) = -(zfar * zNear) / (zfar - zNear);
+    return Result;
+}
+
+
 #endif