fix(#40): remember previous elevation gradient

src/potreeViewer.js

@@ -43,6 +43,9 @@ export async function createPotreeViewer(
     $('#menu_filters').next().show()
     viewer.toggleSidebar()
 
+    // Store the last used elevation gradient 
+    let lastElevationGradient = 'VIRIDIS';
+
     // Helper function to update all point clouds' elevation range
     function updateAllCloudsElevation(range) {
       pointclouds.forEach(pc => {
@@ -75,7 +78,7 @@ export async function createPotreeViewer(
         const high = typeof values[1] === 'number' ? values[1] : 0
 
         updateAllCloudsElevation([low, high])
-        updateAllCloudsGradient('VIRIDIS')
+        updateAllCloudsGradient(lastElevationGradient)
         suppressSidebarAutoScroll(clickCloudIconOnce)
       },
       onActivateAccepted: () => {
@@ -94,9 +97,12 @@ export async function createPotreeViewer(
       if (icon) icon.dispatchEvent(new MouseEvent('click', { bubbles: true }))
     }
 
-    overrideGradientSchemeClick(pointclouds);
+    function setLastElevationGradient(gradientName) {
+      lastElevationGradient = gradientName;
+    }
+    overrideGradientSchemeClick(pointclouds, setLastElevationGradient);
 
-    makeGlobeBackgroundOption()
+    makeGlobeBackgroundOption()     
 
     initMeasurementsPanel(viewer)
     initAnnotationsPanel(viewer)
@@ -309,8 +315,9 @@ function suppressSidebarAutoScroll(action, holdMs = 350) {
  * gradients to multiple point clouds.
  *
  * @param pointclouds - Array of point cloud objects
+ * @param {Function} setLastElevationGradient - Callback function to store the last selected gradient name
  */
-function overrideGradientSchemeClick(pointclouds) {
+function overrideGradientSchemeClick(pointclouds, setLastElevationGradient) {
   const gradientContainer = document.getElementById('elevation_gradient_scheme_selection');
   const spans = gradientContainer.querySelectorAll('span');
   if (spans.length) {
@@ -320,8 +327,9 @@ function overrideGradientSchemeClick(pointclouds) {
         const gradientName = gradientNames[idx];
         if (gradientName) {
           pointclouds.forEach(pc => {
-            pc.material.gradient = Potree.Gradients[gradientName];
+              pc.material.gradient = Potree.Gradients[gradientName];
           });
+          setLastElevationGradient(gradientName);
         }
       };
     });