add noise parameter to the brush settings

data/layout.xml

@@ -155,6 +155,7 @@
             <node height="20" justify="center"><text text="Mixer" font-face="arial" font-size="11"/></node>
             <node height="20" justify="center"><text text="Stencil" font-face="arial" font-size="11"/></node>
             <node height="20" justify="center"><text text="Wet" font-face="arial" font-size="11"/></node>
+            <node height="20" justify="center"><text text="Noise" font-face="arial" font-size="11"/></node>
           </node>
           <border dir="col" align="center" grow="1" width="1" flood-events="1">
             <node height="30" pad="1" width="100%" dir="row">
@@ -183,6 +184,7 @@
             <node height="20" pad="1" width="100%"><slider-h id="tip-mix"/></node>
             <node height="20" pad="1" width="100%"><slider-h id="tip-stencil"/></node>
             <node height="20" pad="1" width="100%"><slider-h id="tip-wet"/></node>
+            <node height="20" pad="1" width="100%"><slider-h id="tip-noise"/></node>
           </border>
         </node>
         

engine/app_shaders.cpp

@@ -258,6 +258,7 @@ void App::initShaders()
         "uniform mediump vec4 col;\n"
         "uniform mediump vec2 resolution;\n"
         "uniform mediump float alpha;\n"
+        "uniform mediump float noise;\n"
         "uniform mediump vec2 stencil_offset;\n"
         "uniform mediump float stencil_alpha;\n"
         "uniform mediump float wet;\n"
@@ -268,6 +269,7 @@ void App::initShaders()
 #else
         "out mediump vec4 frag;\n"
 #endif
+        "mediump float rand(vec2 co) { return fract(sin(dot(co.xy, vec2(12.9898, 78.233))) * 43758.5453); }\n"
         "void main(){\n"
         "   mediump vec2 uv2 = gl_FragCoord.st / resolution;\n"
         "   mediump float stencil = 1.0 - (texture(tex_stencil, (uv2+stencil_offset) * 2.0).r * 0.9) * stencil_alpha;\n"
@@ -278,6 +280,7 @@ void App::initShaders()
 #else
         "   mediump vec4 bg = texture(tex_bg, uv2);\n"
 #endif
+        "   fg.a *= 1.0-rand(uv2+uv)*noise;\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;"

engine/brush.h

@@ -18,6 +18,7 @@ public:
     float m_tip_angle = 0;
     float m_tip_stencil = 0;
     float m_tip_wet = 0;
+    float m_tip_noise = 0;
     bool  m_tip_angle_follow = false;
     bool  m_tip_flow_pressure = false;
     bool  m_tip_size_pressure = false;

engine/canvas.cpp

@@ -247,6 +247,7 @@ void ui::Canvas::stroke_draw()
             //ShaderManager::u_vec2(kShaderUniform::StencilOffset, glm::vec2((rand()%1000)*0.001f, (rand()%1000)*0.001f));
             ShaderManager::u_float(kShaderUniform::StencilAlpha, m_brush.m_tip_stencil);
             ShaderManager::u_float(kShaderUniform::Wet, m_brush.m_tip_wet);
+            ShaderManager::u_float(kShaderUniform::Noise, m_brush.m_tip_noise);
             for (const auto& s : samples)
             {
                 glm::vec2 dx(s.size * 0.5f, 0), dy(0, s.size * 0.5f);

engine/canvas_modes.cpp

@@ -490,7 +490,7 @@ void CanvasModeMaskFree::on_MouseEvent(MouseEvent* me, glm::vec2& loc)
 
 void CanvasModeMaskFree::on_Draw(const glm::mat4& ortho, const glm::mat4& proj, const glm::mat4& camera)
 {
-    if (!m_points.empty())
+    if (m_points.size() > 3)
     {
         if (m_dragging)
         {
@@ -623,7 +623,7 @@ void CanvasModeMaskLine::on_MouseEvent(MouseEvent* me, glm::vec2& loc)
 
 void CanvasModeMaskLine::on_Draw(const glm::mat4& ortho, const glm::mat4& proj, const glm::mat4& camera)
 {
-    if (!m_points.empty())
+    if (m_points.size() > 3)
     {
         if (m_active_tool)
         {

engine/node_panel_stroke.cpp

@@ -29,6 +29,8 @@ void NodePanelStroke::update_controls()
     m_tip_opacity->m_value.x = b.m_tip_opacity;
     m_tip_angle->m_value.x = b.m_tip_angle;
     m_tip_stencil->m_value.x = b.m_tip_stencil;
+    m_tip_wet->m_value.x = b.m_tip_wet;
+    m_tip_noise->m_value.x = b.m_tip_noise;
     m_jitter_scale->m_value.x = b.m_jitter_scale;
     m_jitter_angle->m_value.x = b.m_jitter_angle;
     m_jitter_spread->m_value.x = b.m_jitter_spread;
@@ -55,6 +57,7 @@ void NodePanelStroke::init_controls()
     init_slider(m_tip_angle, "tip-angle", &ui::Brush::m_tip_angle);
     init_slider(m_tip_stencil, "tip-stencil", &ui::Brush::m_tip_stencil);
     init_slider(m_tip_wet, "tip-wet", &ui::Brush::m_tip_wet);
+    init_slider(m_tip_noise, "tip-wet", &ui::Brush::m_tip_noise);
     init_slider(m_jitter_scale, "jitter-scale", &ui::Brush::m_jitter_scale);
     init_slider(m_jitter_angle, "jitter-angle", &ui::Brush::m_jitter_angle);
     init_slider(m_jitter_spread, "jitter-spread", &ui::Brush::m_jitter_spread);

engine/node_panel_stroke.h

@@ -18,6 +18,7 @@ public:
     NodeSliderH* m_tip_angle;
     NodeSliderH* m_tip_stencil;
     NodeSliderH* m_tip_wet;
+    NodeSliderH* m_tip_noise;
     NodeSliderH* m_jitter_scale;
     NodeSliderH* m_jitter_angle;
     NodeSliderH* m_jitter_spread;

engine/shader.h

@@ -24,6 +24,7 @@ enum class kShaderUniform : uint16_t
     Resolution = const_hash("resolution"),
     Highlight = const_hash("highlight"),
     BlendMode = const_hash("blend_mode"),
+    Noise = const_hash("noise"),
 };
 
 enum class kShader : uint16_t