code cleanup and improve brush direction

src/brush.h

@@ -96,6 +96,13 @@ public:
         float fov = 0;
     };
     int m_layer = 0;
+    int m_dir_kp = 0;
+    bool m_dir_valid = false;
+    glm::vec2 m_dir_ref = { 1, 0 };
+    float m_dir_ref_angle = 0;
+    float m_dir_dist = 0;
+    float m_dir_step = 10;
+    float m_dir_angle = 0;
     float m_curve = 0;
     float m_dist = 0;
     float m_step = 0;
@@ -103,7 +110,7 @@ public:
     bool m_filter_points = true;
     Camera m_camera;
     std::shared_ptr<Brush> m_brush;
-    cbuffer<glm::vec2, 3> m_direction;
+    cbuffer<float, 3> m_direction;
     cbuffer<float, 10> m_pressure_buff;
     cbuffer<glm::vec3, 3> m_hsv_jitter;
     StrokeSample m_prev_sample;