diff --git a/engine/app_shaders.cpp b/engine/app_shaders.cpp
index f4f6cbb..0c24424 100644
--- a/engine/app_shaders.cpp
+++ b/engine/app_shaders.cpp
@@ -94,13 +94,15 @@ void App::initShaders()
         "   sum += textureOffset(t, uv, ivec2(-1,  0));\n"
         "   sum += textureOffset(t, uv, ivec2(-1,  1));\n"
         "   sum += textureOffset(t, uv, ivec2( 0, -1));\n"
-    
         "   sum += textureOffset(t, uv, ivec2( 0,  1));\n"
         "   sum += textureOffset(t, uv, ivec2( 1, -1));\n"
         "   sum += textureOffset(t, uv, ivec2( 1,  0));\n"
         "   sum += textureOffset(t, uv, ivec2( 1,  1));\n"
         "   return sum / vec4(9.0);\n"
         "}\n"
+        "vec3 blend_colorDodge(vec4 base, vec4 stroke, float alpha_tot) { return mix(stroke.rgb, mix(base.rgb, base.rgb / (1.0 - stroke.rgb), stroke.a / alpha_tot), base.a / alpha_tot); }\n"
+        "vec3 blend_multiply(vec4 base, vec4 stroke, float alpha_tot) { return mix(stroke.rgb, mix(base.rgb, base.rgb * stroke.rgb, stroke.a / alpha_tot), base.a / alpha_tot); }\n"
+        "vec3 blend_normal(vec4 base, vec4 stroke, float alpha_tot) { return mix(base.rgb, stroke.rgb, stroke.a / alpha_tot); }\n"
         "void main(){\n"
         "   mediump vec2 uv2 = gl_FragCoord.st / vec2(2048) * 20.0;\n"
         "   mediump vec4 base = texture(tex, uv.xy);\n"
@@ -108,9 +110,10 @@ void App::initShaders()
         "   mediump float stencil = pow(texture(tex_stencil, uv2).r, 8.0);\n"
         "   stroke.a = mask ? stroke.a * alpha * blur(tex_mask, uv.xy).r : stroke.a * alpha;\n"
 
+        "   if (base.a == 0.0) { frag = stroke; return; }\n"
         "   mediump float contribution = (1.0 - base.a) * stroke.a;\n"
         "   mediump float alpha_tot = base.a + contribution;"
-        "   mediump vec3 rgb = mix(base.rgb, stroke.rgb, (stroke.a / alpha_tot));\n"
+        "   mediump vec3 rgb = blend_multiply(base, stroke, alpha_tot);\n"
         "   frag = vec4(rgb, (lock ? base.a : alpha_tot));\n"
         "}\n";
 
@@ -267,12 +270,12 @@ void App::initShaders()
 #else
         "   mediump vec4 bg = texture(tex_bg, uv2);\n"
 #endif
-        "   if (fg.a < 1.0/255.0) { frag = bg; return; }\n"
-        "   mediump float contribution = max((1.0 - bg.a) * fg.a, 1.0/255.0) * stencil;\n"
+        "   if (fg.a == 0.0) discard;\n"
+        "   mediump float contribution = (1.0 - bg.a) * fg.a * stencil;\n"
         "   mediump float alpha_tot = bg.a + contribution;"
         "   mediump vec3 rgb = mix(bg.rgb, fg.rgb, fg.a / alpha_tot);\n"
         "   mediump vec4 frag_wet = vec4(rgb, mix(bg.a, max(bg.a, fg.a * stencil), fg.a));\n"
-        "   mediump vec4 frag_dry = vec4(rgb, clamp(alpha_tot, 0.0, 1.0));\n"
+        "   mediump vec4 frag_dry = vec4(rgb, alpha_tot);\n"
         "   frag = mix(frag_dry, frag_wet, wet);\n"
         "}\n";
 
diff --git a/engine/canvas.cpp b/engine/canvas.cpp
index d8bf470..1b338c9 100644
--- a/engine/canvas.cpp
+++ b/engine/canvas.cpp
@@ -710,9 +710,9 @@ void ui::Canvas::resize(int width, int height)
     m_height = height;
     for (int i = 0; i < 6; i++)
     {
-        m_tmp[i].create(width, height);
-        m_tex[i].create(width, height);
-        m_tex2[i].create(width, height);
+        m_tmp[i].create(width, height, -1, GL_RGBA32F);
+        m_tex[i].create(width, height, GL_RGBA32F);
+        m_tex2[i].create(width, height, GL_RGBA8);
     }
     for (auto& l : m_layers)
     {
@@ -725,9 +725,9 @@ bool ui::Canvas::create(int width, int height)
     m_height = height;
     for (int i = 0; i < 6; i++)
     {
-        m_tmp[i].create(width, height);
-        m_tex[i].create(width, height);
-        m_tex2[i].create(width, height); // TODO: destroy before recreating
+        m_tmp[i].create(width, height, -1, GL_RGBA32F);
+        m_tex[i].create(width, height, GL_RGBA32F);
+        m_tex2[i].create(width, height, GL_RGBA8); // TODO: destroy before recreating
     }
     m_sampler.create(GL_NEAREST);
     m_sampler_brush.create();
diff --git a/engine/rtt.cpp b/engine/rtt.cpp
index 54f6678..25a4fca 100644
--- a/engine/rtt.cpp
+++ b/engine/rtt.cpp
@@ -40,7 +40,7 @@ void RTT::destroy()
 //    h = 0;
 }
 
-bool RTT::create(int width, int height, int tex/* = -1*/)
+bool RTT::create(int width, int height, int tex/* = -1*/, GLint internal_format)
 {
     // Destroy any previously created object
     destroy();
@@ -60,7 +60,7 @@ bool RTT::create(int width, int height, int tex/* = -1*/)
 
     glBindTexture(GL_TEXTURE_2D, texID);
     if (tex == -1)
-        glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA8, width, height, 0, GL_RGBA, GL_UNSIGNED_BYTE, 0);
+        glTexImage2D(GL_TEXTURE_2D, 0, internal_format, width, height, 0, GL_RGBA, GL_UNSIGNED_BYTE, 0);
     glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
     glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
     glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_EDGE);
diff --git a/engine/rtt.h b/engine/rtt.h
index 6972b14..01cb89a 100644
--- a/engine/rtt.h
+++ b/engine/rtt.h
@@ -15,7 +15,7 @@ public:
     ~RTT();
 
     void destroy();
-    bool create(int width, int height, int tex = -1);
+    bool create(int width, int height, int tex = -1, GLint internal_format = GL_RGBA8);
     bool recreate() { return create(w, h); }
     void clear(glm::vec4 color = glm::vec4(0));
     void readTextureData(uint8_t* buffer);