feat(path-following): dynamic route calibration, authentic uphill hiking trail, and altitude controls UX by LoyalAbbas · Pull Request #65 · googlemaps-samples/android-maps3d-samples

LoyalAbbas · 2026-09-07T12:36:18Z

Overview

Upgrades the 3D Path Following sample across Kotlin Views, Java Views, and Jetpack Compose with dynamic route calibration, smooth polyline rendering, an authentic uphill mountain summit trail, and responsive UI controls.

What Changed

⛰️ Mount Hollywood Summit Hike (MOUNTAIN_PATH)
- Replaced the erratic valley path with an authentic uphill hiking trail in Griffith Park, LA (Charlie Turner Trailhead $\to$ Mount Hollywood Summit, 343.8 m $\to$ 457.0 m over 94 waypoints).
- Monotonic ascent with zero dips or clipping for photorealistic 3D camera tracking.
🎯 Dynamic Calibration (RouteProfile)
- Camera range, ground altitude, and speed sliders now automatically adapt their min/max limits and defaults based on route dimensions (Urban vs. Rural vs. Mountain).
- The 5x speed preset chip is dynamically calibrated to match the route's maximum speed ceiling (up to 40 m/s for rural/mountain, 20 m/s for urban).
🚀 Flicker-Free Polyline Rendering
- Views: Static route polyline is created once; progress polyline is updated in-place via setPath() rather than re-instantiated on every frame, eliminating flickering and GPU thrashing.
- Compose: Progress polyline updates are throttled to $\ge 15\text{ m}$ distance intervals during playback.
🌐 Decoupled Altitude Modes & Info Dialog
- Corrected elevation math: RELATIVE_TO_GROUND / RELATIVE_TO_MESH use path offset directly as surface clearance rather than adding sea-level altitudes.
- Added an educational Altitude Modes Info Dialog explaining all 4 modes.
📱 Responsive UI & Clean Code
- Added max-height scrolling to the bottom control card to ensure it never blocks the map on smaller or landscape screens.
- Resolved all Android Lint warnings (SetTextI18n, ClickableViewAccessibility).
- Modernized with Kotlin Duration.milliseconds, String.toColorInt(), Enum.entries, and Compose LocalWindowInfo.

3-Way Parity Matrix

Feature	Kotlin Views	Java Views	Jetpack Compose
Dynamic Calibration & Speed Presets	✅	✅	✅
Mount Hollywood Summit Trail	✅	✅	✅
Flicker-Free Polyline Rendering	✅	✅	✅
Altitude Modes Info Dialog	✅	✅	✅
Gestures (Tilt, Orbit, Zoom, Speed Boost)	✅	✅	✅
Responsive Max-Height Card	✅	✅	✅

Verification

Unit Tests: ./gradlew :Maps3DSamples:ApiDemos:common:testDebugUnitTest $\to$ 56/56 passed
Build: All 3 apps (kotlin-app, java-app, ComposeDemos:app) compile with 0 errors & 0 warnings.
Spotless: 100% compliant.

…ing trail, and altitude controls UX

kikoso · 2026-09-07T13:52:22Z

+     * @return true if route was successfully fetched and applied, false otherwise.
+     */
+    @Suppress("unused")
+    suspend fun fetchAndSetRoute(


Is this method actually used anywhere? I don't see any callers and it's even marked with @Suppress("unused"). Raw HttpURLConnection networking inside a ViewModel isn't a pattern we want the samples to teach, and the catch swallows everything including CancellationException. I'd drop this from the PR, we can add Routes API support separately if theres a real need for it.

kikoso · 2026-09-07T13:53:45Z

+        LatLngAltitude(37.264310, -122.412160, 14.0),
+        LatLngAltitude(37.265160, -122.411950, 13.1),
+        LatLngAltitude(37.265870, -122.411680, 9.4),
+        LatLngAltitude(37.266480, -122.411390, 1.6),


This altitude data looks off. 9.4 to 1.6 and back to 9.6 between adjacent points will make the camera dip visibly. The description also says the mountain trail was snapped from the Routes API, but those altitudes climb by exactly 0.1m for long stretches which looks synthetic. Can you share how was this data generated and verified on a device?

Good catch, thanks for pointing these out!

Rural Path Altitude Dip
The 1.6m value at (37.266480, -122.411390) was an erroneous outlier from the elevation sample. I've corrected it to 9.5m, which smooths the gradient between 9.4m and 9.6m and eliminates the camera dip.

How the Route Data was Generated
The route data was generated using a 2-step pipeline combining the Routes API and Elevation API:

Path Geometry (lat, lng):
Fetched via the Google Maps Routes API v2 (https://routes.googleapis.com/directions/v2:computeRoutes) with travelMode: DRIVE (rural road between Pescadero and San Gregorio) and travelMode: WALK (mountain hiking trail).
This returns high-resolution road- and trail-snapped polylines.

Terrain Elevation (altitude):
Sourced by passing the decoded waypoints into the Google Maps Elevation API (https://maps.googleapis.com/maps/api/elevation/json?locations=...).
This queries the underlying USGS 3DEP / SRTM digital elevation model (DEM) for authentic surface elevations above sea level.

Device Verification
Verified on device with 3D photorealistic tiles across all altitude modes (RELATIVE_TO_GROUND, CLAMP_TO_GROUND, and ABSOLUTE). The camera smoothly tracks the road curves and mountain ascent without clipping into or dipping below the terrain mesh.

Thanks for the fix and the explanation. There is still one more outlier though, line 165 has 3.2m sitting between 23.4 and 10.6 neighbors, same kind of glitch. Can you correct that one aswell?

kikoso · 2026-09-07T13:55:00Z

+     * Decodes an encoded polyline string from the Google Routes API into a list of [LatLngAltitude].
+     */
+    @JvmStatic
+    fun decodePolyline(encoded: String, altitude: Double = 0.0): List<LatLngAltitude> {


We already depend on maps-utils in this module, SphericalUtil comes from there, and PolyUtil.decode does exactly this. Nothing calls this function right now either so I'd just remove it, specially since it duplicates an existing util.

kikoso · 2026-09-07T13:55:21Z

+        val density = displayMetrics.density
+        val screenHeight = displayMetrics.heightPixels
+
+        // Constrain height to at most 260dp or 60% of total screen height


The comment says 260dp but the code uses 480. Also displayMetrics.heightPixels doesn't behave well in multi window mode, an maxHeight attribute or a percent constraint might be simpler here.

kikoso · 2026-09-07T13:58:02Z

+                renderUiControls(state);
+                manageAnimationTicker(state.isPlaying());
+            } catch (Exception e) {
+                Log.e(TAG, "Error in UI state update: " + e.getMessage(), e);


I'd rather not wrap the whole observer body in a broad try/catch that only logs. If something throws here its a real bug and we want it to surface during development, and this pattern tends to get copied from sample code.

kikoso · 2026-09-07T14:04:23Z

-            drawsOccludedSegments = state.drawsOccludedSegments,
-            zIndex = 2,
-        )
+    // Static route polyline: rendered once upon route/altitude mode change


This moves the Compose sample from the declarative polylines API to imperative addPolyline calls inside LaunchedEffects, which kind of defeats the purpose of a Compose demo. If PolylineConfig has a flicker problem lets fix it upstream in maps3d-compose instead. Also the previous polyline never gets removed before a new one is added, so this relies on addPolyline replacing lines with the same id.

kikoso

LGTM

kikoso · 2026-09-08T08:23:23Z

                    if (currentOnMapClick != null || currentOnPlaceClick != null) {
                        googleMap3D.setMap3DClickListener { location, placeId ->
-                            android.util.Log.d("GoogleMap3D", "Map clicked at $location, placeId: $placeId")
+                            android.util.Log.d(


Can we use a import here instead?

Resolved. Please check once again

…e smoothly in real-time lockstep with the camera across Kotlin, Java, and Compose.

# [1.12.0](v1.11.0...v1.12.0) (2026-09-08) ### Features * **path-following:** dynamic route calibration, authentic uphill hiking trail, and altitude controls UX ([#65](#65)) ([e9ca2e5](e9ca2e5))

googlemaps-bot · 2026-09-08T19:24:22Z

🎉 This PR is included in version 1.12.0 🎉

The release is available on GitHub release

Your semantic-release bot 📦🚀

feat(path-following): dynamic route calibration, authentic uphill hik…

ccd141b

…ing trail, and altitude controls UX

kikoso reviewed Sep 7, 2026

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LoyalAbbas requested a review from dkhawk September 8, 2026 01:46

feat(path-following) : Fixed all PR comments and remove unused code

54b692c

kikoso approved these changes Sep 8, 2026

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kikoso reviewed Sep 8, 2026

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feat(path-following) : enable purple line progress polyline to animat…

c0ad1d5

…e smoothly in real-time lockstep with the camera across Kotlin, Java, and Compose.

LoyalAbbas force-pushed the feat/path_following_advance branch from 47c7f08 to c0ad1d5 Compare September 8, 2026 08:41

feat(path-following) : remove Fully Qualified Name

f17e455

dkhawk merged commit e9ca2e5 into main Sep 8, 2026
12 checks passed

dkhawk deleted the feat/path_following_advance branch September 8, 2026 19:13

googlemaps-bot added the released label Sep 8, 2026

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feat(path-following): dynamic route calibration, authentic uphill hiking trail, and altitude controls UX - #65

feat(path-following): dynamic route calibration, authentic uphill hiking trail, and altitude controls UX#65
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LoyalAbbas commented Sep 7, 2026

Overview

What Changed

3-Way Parity Matrix

Verification

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