some kind of working

modules/globebrowsing/shaders/asdf_fs.glsl

@@ -25,9 +25,18 @@
 #include "fragment.glsl"
 
 uniform vec3 color;
+uniform float lineWidth;
+uniform float blendFactor;
+
+in vec2 lineCenter;
 
 Fragment getFragment() {
+  double dist = length(lineCenter - gl_FragCoord.xy);
+  float alpha = 0.0;
+  if (dist < lineWidth)
+    alpha = pow(float((lineWidth - dist) / lineWidth), 15);
+
   Fragment frag;
-  frag.color = vec4(color, 1);
+  frag.color = vec4(color, alpha);
   return frag;
 }

modules/globebrowsing/shaders/asdf_vs.glsl

@@ -27,7 +27,12 @@
 layout (location = 0) in vec2 in_position;
 
 uniform dmat4 projectionMatrix;
+uniform vec2 viewport;
+
+out vec2 lineCenter;
 
 void main() {
-  gl_Position = vec4(projectionMatrix * vec4(in_position, 0, 1));
+  vec4 pos = vec4(projectionMatrix * vec4(in_position, 0, 1));
+  gl_Position = pos;
+  lineCenter = 0.5 * (pos.xy + vec2(1)) * viewport;
 }

modules/globebrowsing/src/tileprovider/asdftileprovider.cpp

@@ -424,10 +424,16 @@ void AsdfTileProvider::update() {
         static_cast<GLsizei>(_rendertargetDimensions.y)
     );
 
-    glClearColor(.2f, .2f, .2f, 0.f);
+    //glClearColor(.2f, .2f, .2f, 0.f);
+    glClearColor(.0f, .0f, .0f, 0.f);
     glClear(GL_COLOR_BUFFER_BIT);
 
     _program->activate();
+    _program->setUniform("viewport",
+        glm::vec2(_rendertargetDimensions.x, _rendertargetDimensions.y));
+    _program->setUniform("lineWidth", _lineWidth);
+    const float blend = 2.0;
+    //_program->setUniform("blendFactor", blend);
     _program->setUniform("color", _color);
     _program->setUniform("projectionMatrix", projection);
 
@@ -443,9 +449,10 @@ void AsdfTileProvider::update() {
 
     if (_renderingMode == static_cast<int>(RenderingMode::Lines)) {
         glEnable(GL_LINE_SMOOTH);
+        glEnable(GL_BLEND);
+        //glDepthMask(GL_FALSE);
         glLineWidth(_lineWidth);
         glDrawArrays(GL_LINE_STRIP, 0, points.size());
-        glDisable(GL_LINE_SMOOTH);
     }
     else {
         glPointSize(_lineWidth);