Fail fast on missing terrain assets and recover empty renders

renderer/scene.js

@@ -34,8 +34,8 @@ async function json(path) {
   if (!jsonCache.has(path))
     jsonCache.set(
       path,
-      fetch(path).then((r) => {
-        if (!r.ok) throw new Error(path);
+      fetch(path, { signal: AbortSignal.timeout(60000) }).then((r) => {
+        if (!r.ok) throw new Error(`Minecraft asset ${path}: HTTP ${r.status}`);
         return r.json();
       }),
     );
@@ -183,8 +183,10 @@ window.buildTerrain = async (snapshot) => {
       const bs = await json(resourcePath(name, "blockstates") + ".json");
       for (const v of selectModels(bs, props))
         variants.push({ v, m: await model(v.model) });
-    } catch {
+    } catch (error) {
       unsupported.add(name);
+      if (unsupported.size <= 8)
+        console.warn(`Missing block model ${name}: ${error.message}`);
     }
     stateCache.set(s, variants);
     return variants;
@@ -225,6 +227,18 @@ const directions = {
     [0, 1, 0],
   ],
 };
+function renderScene(camera, requireGeometry = false) {
+  if (gl.isContextLost())
+    throw new Error("Graphics context lost while rendering terrain");
+  renderer.render(scene, camera);
+  const error = gl.getError();
+  if (error !== gl.NO_ERROR)
+    throw new Error(`WebGL failed to render terrain (error ${error})`);
+  if (requireGeometry && renderer.info.render.triangles === 0)
+    throw new Error(
+      "Surface-map camera sees no terrain geometry. Check world coordinates and Minecraft assets.",
+    );
+}
 window.renderFace = (p, face, size) => {
   renderer.setSize(size, size);
   const camera = new THREE.PerspectiveCamera(90, 1, 0.05, 512);
@@ -232,7 +246,7 @@ window.renderFace = (p, face, size) => {
   const [dir, up] = directions[face];
   camera.up.set(...up);
   camera.lookAt(p.x + dir[0], p.y + dir[1], p.z + dir[2]);
-  renderer.render(scene, camera);
+  renderScene(camera);
   return renderer.domElement.toDataURL("image/webp", 0.85);
 };
 window.renderMap = (size) => {
@@ -249,7 +263,7 @@ window.renderMap = (size) => {
   camera.position.set((b.minX + b.maxX) / 2, 512, (b.minZ + b.maxZ) / 2);
   camera.up.set(0, 0, -1);
   camera.lookAt(camera.position.x, 0, camera.position.z);
-  renderer.render(scene, camera);
+  renderScene(camera, true);
   return renderer.domElement.toDataURL("image/webp", 0.9);
 };
 window.rendererReady = true;