fix 26 channel color offset

src/core/src/app.rs

@@ -133,7 +133,6 @@ impl App {
         //let exec = Rc::new(RefCell::new(TaskExecutor::new()));
 
         let projection = ProjectionType::Sin(mapproj::zenithal::sin::Sin);
-        gl.enable(WebGl2RenderingContext::BLEND);
 
         // TODO: https://caniuse.com/?search=scissor is not supported for safari <= 14.1
         // When it will be supported nearly everywhere, we will need to uncomment this line to
@@ -829,6 +828,7 @@ impl App {
             // Render the scene
             // Clear all the screen first (only the region set by the scissor)
             gl.clear(WebGl2RenderingContext::COLOR_BUFFER_BIT);
+
             // set the blending options
             layers.draw(camera, shaders, colormaps, projection)?;
 

src/core/src/renderable/mod.rs

@@ -213,9 +213,13 @@ impl Layers {
         let raytracer = &self.raytracer;
         let raytracing = camera.is_raytracing(projection);
 
+        // The first layer or the background must be plot with no blending
+        self.gl.disable(WebGl2RenderingContext::BLEND);
+
         // Check whether a hips to plot is allsky
         // if neither are, we draw a font
         // if there are, we do not draw nothing
+
         let mut idx_start_layer = -1;
 
         for (idx, layer) in self.layers.iter().enumerate() {
@@ -235,6 +239,8 @@ impl Layers {
             }
         }
 
+        let mut blending_enabled = false;
+
         // Need to render transparency font
         if idx_start_layer == -1 {
             let vao = if raytracing {
@@ -258,6 +264,9 @@ impl Layers {
 
             // The background (index -1) has been drawn, we can draw the first HiPS
             idx_start_layer = 0;
+
+            self.gl.enable(WebGl2RenderingContext::BLEND);
+            blending_enabled = true;
         }
 
         let layers_to_render = &self.layers[(idx_start_layer as usize)..];
@@ -283,6 +292,11 @@ impl Layers {
                     }
                 }
             }
+
+            if !blending_enabled {
+                self.gl.enable(WebGl2RenderingContext::BLEND);
+                blending_enabled = true;
+            }
         }
 
         Ok(())