feat(Rendering): report missing view node profile imports

fixes #3343

Author: daker

Documentation/docs/concepts_profile.md

@@ -0,0 +1,47 @@
+---
+title: Rendering Profiles
+---
+
+# Rendering Profiles
+
+VTK.js rendering profiles are side-effect imports that register rendering implementations for classes used by the scene graph. They keep applications smaller by letting you import only the rendering backends and mapper support you need.
+
+## Why profiles exist
+
+Many VTK.js classes are pure pipeline or data-model classes. They only become renderable after a matching rendering profile registers the view-node overrides required by the active backend such as OpenGL or WebGPU.
+
+Without the relevant profile import, VTK.js can still construct the data objects, actors, mappers, and pipeline, but rendering may fail when the scene graph asks `ViewNodeFactory` to create a backend-specific implementation for one of those classes.
+
+## Typical usage
+
+Import a profile near your application entry point before creating the render window content:
+
+```js
+import '@kitware/vtk.js/Rendering/Profiles/Geometry';
+```
+
+If you need broader coverage, import the combined profile:
+
+```js
+import '@kitware/vtk.js/Rendering/Profiles/All';
+```
+
+## Common profiles
+
+- `Geometry`: core polygonal rendering support.
+- `Volume`: image and volume rendering support.
+- `Glyph`: glyph-specific mapper support.
+- `Molecule`: sphere and stick mapper support.
+- `LIC`: line integral convolution rendering support.
+- `All`: imports all supported profiles.
+
+## When a profile is missing
+
+A missing profile often shows up as an error from `Rendering/SceneGraph/ViewNodeFactory` saying that no implementation was found for a class and that a rendering profile is likely missing.
+
+That warning means one of these is true:
+
+- A built-in renderable class is being used without importing the profile that registers its rendering implementation.
+- A custom renderable class has not been registered with the view-node factory.
+
+If you are unsure which profile is required, importing `Rendering/Profiles/All` is the easiest way to confirm that the issue is profile-related. After that, you can narrow it back down to the smallest profile set your application needs.

Documentation/scripts/generate-sidebar-config.mjs

@@ -36,7 +36,10 @@ const docsMenu = [
   },
   {
     text: 'Concepts',
-    items: [{ text: 'Widgets', link: 'concepts_widgets.html' }],
+    items: [
+      { text: 'Widgets', link: 'concepts_widgets.html' },
+      { text: 'Profiles', link: 'concepts_profile.html' },
+    ],
   },
   {
     text: 'Miscellaneous',

Sources/Rendering/SceneGraph/ViewNodeFactory/index.js

@@ -1,5 +1,28 @@
 import macro from 'vtk.js/Sources/macros';
 
+function listClassHierarchy(dataObject) {
+  const classNames = [];
+  let depth = 0;
+  let className = dataObject.getClassName(depth++);
+  while (className) {
+    classNames.push(className);
+    className = dataObject.getClassName(depth++);
+  }
+  return classNames;
+}
+
+function buildMissingImplementationMessage(factoryName, classNames) {
+  const classList = classNames.join(' → ');
+  return [
+    `No ${factoryName} implementation found for ${classNames[0]}.`,
+    `Class hierarchy: ${classList}.`,
+    `A rendering Profile is likely missing for ${classNames[0]}.`,
+    "Try importing '@kitware/vtk.js/Rendering/Profiles/All' or 'vtk.js/Sources/Rendering/Profiles/All',",
+    'or import the specific rendering profile needed by this renderable if known.',
+    'See https://kitware.github.io/vtk-js/docs/concepts_profile.html for details.',
+  ].join('\n');
+}
+
 // ----------------------------------------------------------------------------
 // vtkViewNodeFactory methods
 // ----------------------------------------------------------------------------
@@ -18,8 +41,9 @@ function vtkViewNodeFactory(publicAPI, model) {
       return null;
     }
 
+    const classNames = listClassHierarchy(dataObject);
     let cpt = 0;
-    let className = dataObject.getClassName(cpt++);
+    let className = classNames[cpt++];
     let isObject = false;
     const keys = Object.keys(model.overrides);
     while (className && !isObject) {
@@ -31,7 +55,9 @@ function vtkViewNodeFactory(publicAPI, model) {
     }
 
     if (!isObject) {
-      return null;
+      throw new Error(
+        buildMissingImplementationMessage(publicAPI.getClassName(), classNames)
+      );
     }
     const vn = model.overrides[className]();
     vn.setMyFactory(publicAPI);