Smoother alpha transition in mixing view. Also force use of opacity

blending in mixing view for clarity.

Shader.cpp

@@ -170,6 +170,8 @@ void ShadingProgram::checkLinkingErr()
 }
 
 
+bool Shader::force_blending_opacity = false;
+
 Shader::Shader() : blending(BLEND_OPACITY)
 {
     // create unique id
@@ -209,13 +211,20 @@ void Shader::use()
     program_->setUniform("iResolution", iResolution);
 
     // Blending Function
-    if ( blending != BLEND_CUSTOM) {
+    if (force_blending_opacity) {
+        glEnable(GL_BLEND);
+        glBlendEquation(blending_equation[BLEND_OPACITY]);
+        glBlendFunc(blending_source_function[BLEND_OPACITY], blending_destination_function[BLEND_OPACITY]);
+
+    }
+    else if ( blending != BLEND_CUSTOM ) {
         glEnable(GL_BLEND);
         glBlendEquation(blending_equation[blending]);
         glBlendFunc(blending_source_function[blending], blending_destination_function[blending]);
 
-//        glBlendEquationSeparate(blending_equation[blending], GL_FUNC_ADD);
-//        glBlendFuncSeparate(blending_source_function[blending], blending_destination_function[blending], GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA);
+        // TODO different blending for alpha and color
+        //        glBlendEquationSeparate(blending_equation[blending], GL_FUNC_ADD);
+        //        glBlendFuncSeparate(blending_source_function[blending], blending_destination_function[blending], GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA);
 
     }
     else

Shader.h

@@ -65,6 +65,8 @@ public:
     } BlendMode;
     BlendMode blending;
 
+    static bool force_blending_opacity;
+
 protected:
     ShadingProgram *program_;
     glm::vec3 iResolution;

Source.cpp

@@ -255,6 +255,18 @@ void Source::setActive (bool on)
     groups_[View::LAYER]->visible_ = active_;
 
 }
+// Transfer functions from coordinates to alpha (1 - transparency)
+float linear_(float x, float y) {
+    return 1.f - CLAMP( sqrt( ( x * x ) + ( y * y ) ), 0.f, 1.f );
+}
+
+float quad_(float x, float y) {
+    return 1.f - CLAMP( ( x * x ) + ( y * y ), 0.f, 1.f );
+}
+
+float sin_quad(float x, float y) {
+    return 0.5f + 0.5f * cos( M_PI * CLAMP( ( ( x * x ) + ( y * y ) ), 0.f, 1.f ) );
+}
 
 void Source::update(float dt)
 {
@@ -267,8 +279,8 @@ void Source::update(float dt)
         // ADJUST alpha based on MIXING node
         // read position of the mixing node and interpret this as transparency of render output
         glm::vec2 dist = glm::vec2(groups_[View::MIXING]->translation_);
-        float alpha = 1.0 - CLAMP( ( dist.x * dist.x ) + ( dist.y * dist.y ), 0.f, 1.f );
-        blendingshader_->color.a = alpha;
+        // use the prefered transfer function
+        blendingshader_->color.a = sin_quad( dist.x, dist.y );
 
         // CHANGE update status based on limbo
         setActive( glm::length(dist) < 1.3f );

View.cpp

@@ -243,6 +243,16 @@ MixingView::MixingView() : View(MIXING), limbo_scale_(1.3f)
 }
 
 
+void MixingView::draw()
+{
+    // temporarily force shaders to use opacity blending for rendering icons
+    Shader::force_blending_opacity = true;
+    // draw scene of this view
+    scene.root()->draw(glm::identity<glm::mat4>(), Rendering::manager().Projection());
+    // restore state
+    Shader::force_blending_opacity = false;
+}
+
 void MixingView::zoom( float factor )
 {
     float z = scene.root()->scale_.x;
@@ -331,6 +341,10 @@ void MixingView::setAlpha(Source *s)
     s->touch();
 }
 
+float sin_quad_texture(float x, float y) {
+    return 0.5f + 0.5f * cos( M_PI * CLAMP( ( ( x * x ) + ( y * y ) ) / CIRCLE_PIXEL_RADIUS, 0.f, 1.f ) );
+}
+
 uint MixingView::textureMixingQuadratic()
 {
     static GLuint texid = 0;
@@ -349,14 +363,16 @@ uint MixingView::textureMixingQuadratic()
             c = -CIRCLE_PIXELS / 2 + 1;
             for (int j=0; j < CIRCLE_PIXELS / 2; ++j) {
                 // distance to the center
-                distance = (GLfloat) ((c * c) + (l * l)) / CIRCLE_PIXEL_RADIUS;
-//                distance = (GLfloat) sqrt( (GLfloat) ((c * c) + (l * l))) / (GLfloat) sqrt(CIRCLE_PIXEL_RADIUS); // linear
-                // luminance
-                luminance = 255.f * CLAMP( 0.95f - 0.8f * distance, 0.f, 1.f);
-                color[0] = color[1] = color[2] = static_cast<GLubyte>(luminance);
-                // alpha
-                alpha = 255.f * CLAMP( 1.f - distance , 0.f, 1.f);
+                distance = sin_quad_texture( (float) c , (float) l  );
+//                distance = 1.f - (GLfloat) ((c * c) + (l * l)) / CIRCLE_PIXEL_RADIUS;  // quadratic
+//                distance = 1.f - (GLfloat) sqrt( (GLfloat) ((c * c) + (l * l))) / (GLfloat) sqrt(CIRCLE_PIXEL_RADIUS); // linear
+
+                // transparency
+                alpha = 255.f * CLAMP( distance , 0.f, 1.f);
                 color[3] = static_cast<GLubyte>(alpha);
+                // luminance adjustment
+                luminance = 255.f * CLAMP( 0.2f + 0.75f * distance, 0.f, 1.f);
+                color[0] = color[1] = color[2] = static_cast<GLubyte>(luminance);
 
                 // 1st quadrant
                 memmove(&matrix[ j * 4 + i * CIRCLE_PIXELS * 4 ], color, 4);

View.h

@@ -88,6 +88,7 @@ class MixingView : public View
 public:
     MixingView();
 
+    void draw () override;
     void zoom (float factor) override;
     void centerSource(Source *) override;