diff --git a/engine/app.cpp b/engine/app.cpp
index 3fa5bb8..538e141 100644
--- a/engine/app.cpp
+++ b/engine/app.cpp
@@ -414,10 +414,10 @@ void App::initLayout()
                 //exit(0); 
                 if (canvas)
                 {
-                    canvas->m_canvas->snapshot_save(data_path);
-                    canvas->m_canvas->m_use_instanced = !canvas->m_canvas->m_use_instanced;
+                    canvas->m_canvas->save(data_path);
+                    //canvas->m_canvas->m_use_instanced = !canvas->m_canvas->m_use_instanced;
                     //button->color_normal = canvas->m_canvas->m_use_instanced ? glm::vec4(1, 0, 0, 1) : glm::vec4(0, 1, 0, 1);
-                    button->m_text->set_text(canvas->m_canvas->m_use_instanced ? "INST" : "NORM");
+                    //button->m_text->set_text(canvas->m_canvas->m_use_instanced ? "INST" : "NORM");
                 }
             };
             button->m_text->set_text("NORM");
diff --git a/engine/canvas.cpp b/engine/canvas.cpp
index 0e1218a..2317e70 100644
--- a/engine/canvas.cpp
+++ b/engine/canvas.cpp
@@ -400,6 +400,69 @@ void ui::Canvas::clear_context()
     }
 };
 
+void ui::Canvas::save(std::string data_path)
+{
+    // save viewport and clear color states
+    GLint vp[4];
+    GLfloat cc[4];
+    glGetIntegerv(GL_VIEWPORT, vp);
+    glGetFloatv(GL_COLOR_CLEAR_VALUE, cc);
+    GLboolean blend = glIsEnabled(GL_BLEND);
+
+    // prepare common states
+    glViewport(0, 0, m_width, m_height);
+    glDisable(GL_BLEND);
+
+    for (int i = 0; i < 6; i++)
+    {
+        m_tmp[i].bindFramebuffer();
+        m_tmp[i].clear({ 1, 1, 1, 1 });
+
+        for (auto layer_index : m_order)
+        {
+            // copy to tmp2 for layer blending
+            glActiveTexture(GL_TEXTURE0);
+            m_tex2[i].bind();
+            glCopyTexSubImage2D(GL_TEXTURE_2D, 0, 0, 0, 0, 0, m_width, m_height);
+            m_tex2[i].unbind();
+
+            m_layers[layer_index].m_rtt[i].bindTexture();
+            glActiveTexture(GL_TEXTURE1);
+            m_tex2[i].bind();
+            m_sampler.bind(0);
+            m_sampler_bg.bind(1);
+            ShaderManager::use(ui::kShader::StrokeLayer);
+            ShaderManager::u_int(kShaderUniform::TexBG, 1);
+            ShaderManager::u_float(kShaderUniform::Alpha, m_layers[layer_index].m_opacity);
+            ShaderManager::u_int(kShaderUniform::Tex, 0);
+            ShaderManager::u_mat4(kShaderUniform::MVP, glm::ortho(-.5f, .5f, -.5f, .5f, -1.f, 1.f));
+            m_plane.draw_fill();
+            m_sampler.unbind();
+            m_sampler_bg.unbind();
+            m_tex2[i].unbind();
+            m_layers[layer_index].m_rtt[i].unbindTexture();
+        }
+
+        m_tmp[i].unbindFramebuffer();
+    }
+
+    auto data = std::make_unique<uint8_t[]>(m_tmp[0].bytes());
+    for (int i = 0; i < 6; i++)
+    {
+        m_tmp[i].readTextureData(data.get());
+        static char name[128];
+        sprintf(name, "%s/Face%d.png", data_path.c_str(), i);
+        LOG("writing %s", name);
+        int ret = stbi_write_png(name, m_tmp[i].getWidth(), m_tmp[i].getHeight(), 4, data.get(), m_tmp[i].stride());
+    }
+
+    // restore viewport and clear color states
+    blend ? glEnable(GL_BLEND) : glDisable(GL_BLEND);
+    glViewport(vp[0], vp[1], vp[2], vp[3]);
+    glClearColor(cc[0], cc[1], cc[2], cc[3]);
+    glActiveTexture(GL_TEXTURE0);
+}
+
 ///////////////////////////////////////////////////////////////////////////////////////////
 
 void ui::Layer::destroy()
diff --git a/engine/canvas.h b/engine/canvas.h
index b06d962..d6acf3b 100644
--- a/engine/canvas.h
+++ b/engine/canvas.h
@@ -75,6 +75,7 @@ public:
     void snapshot_save(std::string data_path);
     void snapshot_restore();
     void clear_context();
+    void save(std::string data_path);
 };