diff --git a/toonz/sources/tnztools/assistant.cpp b/toonz/sources/tnztools/assistant.cpp
index 25f9d13..5e0ec9c 100644
--- a/toonz/sources/tnztools/assistant.cpp
+++ b/toonz/sources/tnztools/assistant.cpp
@@ -66,8 +66,9 @@ TGuideline::calcTrackWeight(const TTrack &track, const TAffine &toScreen, bool &
   double sumDeviation = 0.0;
 
   TPointD prev = toScreen*track[0].position;
-  for(int i = 0; i < track.size(); ++i) {
+  for(int i = 1; i < track.size(); ++i) {
     const TTrackPoint &tp = track[i];
+    TTrackPoint mid = TTrack::interpolationLinear(track[i-1], track[i], 0.5);
     TPointD p = toScreen*tp.position;
     double length = tdistance(p, prev);
     sumLength += length;
@@ -77,7 +78,7 @@ TGuideline::calcTrackWeight(const TTrack &track, const TAffine &toScreen, bool &
       double weight = length*logNormalDistribuitionUnscaled(midStepLength, snapLenght, snapScale);
       sumWeight += weight;
 
-      TTrackPoint ntp = transformPoint(tp);
+      TTrackPoint ntp = transformPoint(mid);
       double deviation = tdistance(toScreen*ntp.position, p);
       sumDeviation += weight*deviation;
     }
diff --git a/toonz/sources/tnztools/fullcolorbrushtool.cpp b/toonz/sources/tnztools/fullcolorbrushtool.cpp
index 321e23f..0204fe0 100644
--- a/toonz/sources/tnztools/fullcolorbrushtool.cpp
+++ b/toonz/sources/tnztools/fullcolorbrushtool.cpp
@@ -289,7 +289,7 @@ bool FullColorBrushTool::askWrite(const TRect &rect) {
 
 bool FullColorBrushTool::preLeftButtonDown() {
   m_modifierAssistants->drawOnly = !FullcolorAssistants;
-  m_inputmanager.drawPreview = !m_modifierAssistants->drawOnly;
+  m_inputmanager.drawPreview = false; //!m_modifierAssistants->drawOnly;
   
   m_inputmanager.clearModifiers();
   m_inputmanager.addModifier( TInputModifierP(m_modifierTangents.getPointer()) );