fixing stroke direction

src/brush.h

@@ -146,15 +146,33 @@ public:
         glm::vec3 pos = { 0, 0, 0 };
         float pressure = 0;
         float dist = 0;
+        glm::vec2 dir = { 0, 0 };
     };
     struct Camera
     {
         glm::mat4 rot;
         float fov = 0;
     };
+    struct SamplesInterpolator
+    {
+        Keypoint last;
+        std::vector<Keypoint> keypoints;
+        bool ready_first;
+        bool first;
+        float spacing;
+        float dist;
+        SamplesInterpolator() noexcept;
+        SamplesInterpolator(float sp) noexcept;
+        void add(const Keypoint& p) noexcept;
+        bool ready() const noexcept;
+        void reset(bool clear_keypoints) noexcept;
+        std::vector<Keypoint> compute() noexcept;
+    };
     int m_layer = 0;
     int m_dir_kp = 0;
     bool m_dir_valid = false;
+    std::vector<Keypoint> m_dirs_cache;
+    int m_dir_i = 0;
     glm::vec2 m_dir_ref = { 1, 0 };
     float m_dir_ref_angle = 0;
     float m_dir_dist = 0;
@@ -183,7 +201,10 @@ public:
     void reset(bool clear_keypoints = false);
     bool has_sample();
     std::vector<StrokeSample> compute_samples();
+    std::vector<StrokeSample> compute_samples_old();
     StrokeSample randomize_sample(const glm::vec3& pos, float pressure, float curve_angle);
+    SamplesInterpolator m_interp_main;
+    SamplesInterpolator m_interp_dir;
 
     void randomize_prng();
     float rnd_nor() { return float((double)prng() / (double)prng.max()); };                     // normalized [0, +1]