diff --git a/src/brush.cpp b/src/brush.cpp
index 9168f6d..1c752ac 100644
--- a/src/brush.cpp
+++ b/src/brush.cpp
@@ -53,7 +53,7 @@ void Stroke::randomize_prng()
 
 std::vector<StrokeSample> Stroke::compute_samples()
 {
-    if (m_keypoints.empty()) return {};
+    if (m_keypoints.size() < 2) return {};
     int nsamples = (int)glm::floor((m_keypoints.back().dist - m_dist) / m_step);
     std::vector<StrokeSample> samples;
     samples.reserve(nsamples); // preallocate the estimate number of samples
@@ -62,7 +62,7 @@ std::vector<StrokeSample> Stroke::compute_samples()
         m_dist += m_step;
         m_dir_dist += m_step;
         int old_kp = m_last_kp;
-        while (m_dist > m_keypoints[m_last_kp + 1].dist)
+        while (m_dist > m_keypoints[m_last_kp + 1].dist && m_last_kp < m_keypoints.size())
             m_last_kp++;
         const auto& A = m_keypoints[old_kp];
         const auto& B = m_keypoints[m_last_kp == old_kp ? m_last_kp + 1 : m_last_kp]; // NOTE: this should be true when while is true
@@ -127,6 +127,14 @@ std::vector<StrokeSample> Stroke::compute_samples()
         }
         else
         {
+            static bool invalid_logged = false;
+            if (!invalid_logged)
+            {
+                for (auto const& p : m_keypoints)
+                    LOG("point dist %f pos %f %f %f", p.dist, p.pos.x, p.pos.y, p.pos.z);
+                invalid_logged = true;
+            }
+            LOG("A.dist %f B.dist %f", A.dist, B.dist);
             LOG("Invalid sample");
         }
     }
@@ -134,7 +142,7 @@ std::vector<StrokeSample> Stroke::compute_samples()
 }
 bool Stroke::has_sample()
 {
-    return m_keypoints.empty() ? false :                // no keypoints
+    return m_keypoints.size() < 2 ? false :             // no keypoints
         (m_keypoints.back().dist > (m_dist + m_step));  // check if next kp is closer than spacing
 }
 void Stroke::reset(bool clear_keypoints /*= false*/)