Made imagerySplitPosition use absolute coordinates

Apps/Sandcastle/gallery/Imagery Layers Split.html

@@ -66,7 +66,7 @@
 
 // Sync the position of the slider with the split position
 var slider = document.getElementById('slider');
-viewer.scene.imagerySplitPosition = (slider.offsetLeft) / slider.parentElement.offsetWidth;
+viewer.scene.imagerySplitPosition = slider.offsetLeft;
 
 var dragStartX = 0;
 
@@ -87,9 +87,15 @@
   var slider = document.getElementById('slider');
   var splitPosition = (e.clientX - dragStartX) / slider.parentElement.offsetWidth;
   slider.style.left = 100.0 * splitPosition + "%";
-  viewer.scene.imagerySplitPosition = splitPosition;
+  viewer.scene.imagerySplitPosition = slider.offsetLeft;
 }
 
+// Update the slider position each frame to account for window resizing.
+viewer.scene.preRender.addEventListener(function(scene, time) {
+    var slider = document.getElementById('slider');
+    viewer.scene.imagerySplitPosition = slider.offsetLeft;
+});
+
 
 //Sandcastle_End
     Sandcastle.finishedLoading();

Source/Renderer/AutomaticUniforms.js

@@ -1469,7 +1469,7 @@ define([
 
          /**
          * An automatic GLSL uniform representing the splitter position to use when rendering imagery layers with a splitter.
-         * This will be in the range 0.0 to 1.0 with 0.0 being the far left of the viewport and 1.0 being the far right of the viewport.
+         * This will be in pixel coordinates relative to the canvas.
          *
          * @alias czm_imagerySplitPosition
          * @glslUniform

Source/Shaders/GlobeFS.glsl

@@ -99,7 +99,7 @@ vec4 sampleAndBlend(
     float alpha = value.a;
 
 #ifdef APPLY_SPLIT
-    float splitPosition = czm_imagerySplitPosition * czm_viewport.z;
+    float splitPosition = czm_imagerySplitPosition;
     // Split to the left
     if (split < 0.0 && gl_FragCoord.x > splitPosition) {
        alpha = 0.0;