diff --git a/data/layout.xml b/data/layout.xml
index 2ff1b1e..1288d9b 100644
--- a/data/layout.xml
+++ b/data/layout.xml
@@ -113,13 +113,15 @@
           <node width="30%" dir="col">
             <node height="20" justify="center"><text text="Size" font-face="arial" font-size="11"/></node>
             <node height="20" justify="center"><text text="Flow" font-face="arial" font-size="11"/></node>
+            <node height="20" justify="center"><text text="Opacity" font-face="arial" font-size="11"/></node>
             <node height="20" justify="center"><text text="Spacing" font-face="arial" font-size="11"/></node>
             <node height="20" justify="center"><text text="Angle" font-face="arial" font-size="11"/></node>
             <node height="20" justify="center"><text text="Mixer" font-face="arial" font-size="11"/></node>
           </node>
           <border dir="col" align="center" grow="1" width="1">
             <node height="20" pad="1" width="100%"><slider-h id="tip-size" value=".5"/></node>
-            <node height="20" pad="1" width="100%"><slider-h id="tip-flow" value=".25"/></node>
+            <node height="20" pad="1" width="100%"><slider-h id="tip-flow" value=".15"/></node>
+            <node height="20" pad="1" width="100%"><slider-h id="tip-opacity" value="1"/></node>
             <node height="20" pad="1" width="100%"><slider-h id="tip-spacing" value=".25"/></node>
             <node height="20" pad="1" width="100%"><slider-h id="tip-angle"/></node>
             <node height="20" pad="1" width="100%"><slider-h id="tip-mix"/></node>
diff --git a/engine/brush.h b/engine/brush.h
index 7a7caf0..7415398 100644
--- a/engine/brush.h
+++ b/engine/brush.h
@@ -14,6 +14,7 @@ public:
     float m_tip_size;
     float m_tip_spacing;
     float m_tip_flow;
+    float m_tip_opacity;
     float m_tip_angle;
     float m_jitter_scale;
     float m_jitter_angle;
diff --git a/engine/canvas.cpp b/engine/canvas.cpp
index 1a5177f..f3651c8 100644
--- a/engine/canvas.cpp
+++ b/engine/canvas.cpp
@@ -24,8 +24,8 @@ void ui::Canvas::clear()
 }
 void ui::Canvas::stroke_end()
 {
-    m_current_stroke = nullptr;
     stroke_commit();
+    m_current_stroke = nullptr;
     m_show_tmp = false;
 }
 void ui::Canvas::stroke_draw()
@@ -33,6 +33,8 @@ void ui::Canvas::stroke_draw()
     if (!(m_current_stroke && m_current_stroke->has_sample()))
         return;
 
+    m_dirty = true;
+
     m_tmp.bindFramebuffer();
 
     GLint vp[4];
@@ -134,6 +136,10 @@ void ui::Canvas::stroke_draw()
 }
 void ui::Canvas::stroke_commit()
 {
+    if (!m_dirty)
+        return;
+    m_dirty = false;
+
     m_fb.bindFramebuffer();
 
     // copy to tmp2 for layer blending
@@ -158,7 +164,7 @@ void ui::Canvas::stroke_commit()
     ShaderManager::use(ui::kShader::StrokeLayer);
     ShaderManager::u_int(kShaderUniform::Tex, 0);
     ShaderManager::u_int(kShaderUniform::TexBG, 1);
-    ShaderManager::u_float(kShaderUniform::Alpha, .5); // TODO: if using opacity in commit, update blending to match the preview when rendering m_tmp in NodeCanvas
+    ShaderManager::u_float(kShaderUniform::Alpha, m_current_stroke->m_brush.m_tip_opacity); // TODO: if using opacity in commit, update blending to match the preview when rendering m_tmp in NodeCanvas
     ShaderManager::u_mat4(kShaderUniform::MVP, glm::ortho(-.5f, .5f, -.5f, .5f, -1.f, 1.f));
     m_plane.draw_fill();
     m_sampler.unbind();
diff --git a/engine/canvas.h b/engine/canvas.h
index 1b3a69e..50256d8 100644
--- a/engine/canvas.h
+++ b/engine/canvas.h
@@ -9,14 +9,15 @@ NS_START
 
 class Canvas
 {
-    Stroke* m_current_stroke = nullptr;
     Plane m_plane;
     BrushMesh m_mesh;
     int m_current_layer_idx = 0;
+    bool m_dirty = false;
 public:
     int m_width;
     int m_height;
     bool m_use_instanced = false;
+    Stroke* m_current_stroke = nullptr;
     bool m_show_tmp = false;
     std::vector<Layer> m_layers;
     std::vector<Stroke> m_strokes;
diff --git a/engine/layout.h b/engine/layout.h
index 1632d2a..8155b0c 100644
--- a/engine/layout.h
+++ b/engine/layout.h
@@ -1798,6 +1798,7 @@ public:
     NodeSliderH* m_tip_size;
     NodeSliderH* m_tip_spacing;
     NodeSliderH* m_tip_flow;
+    NodeSliderH* m_tip_opacity;
     NodeSliderH* m_tip_angle;
     NodeSliderH* m_jitter_scale;
     NodeSliderH* m_jitter_angle;
@@ -1822,6 +1823,7 @@ public:
         init_slider(m_tip_size, "tip-size", &ui::Brush::m_tip_size);
         init_slider(m_tip_spacing, "tip-spacing", &ui::Brush::m_tip_spacing);
         init_slider(m_tip_flow, "tip-flow", &ui::Brush::m_tip_flow);
+        init_slider(m_tip_opacity, "tip-opacity", &ui::Brush::m_tip_opacity);
         init_slider(m_tip_angle, "tip-angle", &ui::Brush::m_tip_angle);
         init_slider(m_jitter_scale, "jitter-scale", &ui::Brush::m_jitter_scale);
         init_slider(m_jitter_angle, "jitter-angle", &ui::Brush::m_jitter_angle);
@@ -1904,7 +1906,7 @@ public:
             ui::ShaderManager::use(kShader::TextureAlpha);
             ui::ShaderManager::u_int(kShaderUniform::Tex, 0);
             ui::ShaderManager::u_mat4(kShaderUniform::MVP, mvp);
-            ui::ShaderManager::u_float(kShaderUniform::Alpha, .5);
+            ui::ShaderManager::u_float(kShaderUniform::Alpha, m_canvas->m_current_stroke->m_brush.m_tip_opacity);
             m_canvas->m_tmp.bindTexture();
             NodeBorder::m_plane.draw_fill();
             m_canvas->m_tmp.unbindTexture();