clarify altitude

include/mbgl/map/camera.hpp

@@ -21,8 +21,8 @@ struct CameraOptions {
         center = o;
         return *this;
     }
-    CameraOptions& withAlt(const std::optional<double>& o) {
-        altM = o;
+    CameraOptions& withCenterAltitude(const std::optional<double>& o) {
+        centerAltitude = o;
         return *this;
     }
     CameraOptions& withPadding(const std::optional<EdgeInsets>& p) {
@@ -57,7 +57,7 @@ struct CameraOptions {
     /** Coordinate at the center of the map. */
     std::optional<LatLng> center;
 
-    std::optional<double> altM;
+    std::optional<double> centerAltitude;
 
     /** Padding around the interior of the view that affects the frame of
         reference for `center`. */
@@ -84,7 +84,7 @@ struct CameraOptions {
 
 constexpr bool operator==(const CameraOptions& a, const CameraOptions& b) {
     return a.center == b.center && a.padding == b.padding && a.anchor == b.anchor && a.zoom == b.zoom &&
-           a.bearing == b.bearing && a.pitch == b.pitch && a.roll == b.roll && a.fov == b.fov && a.altM == b.altM;
+           a.bearing == b.bearing && a.pitch == b.pitch && a.roll == b.roll && a.fov == b.fov && a.centerAltitude == b.centerAltitude;
 }
 
 constexpr bool operator!=(const CameraOptions& a, const CameraOptions& b) {

src/mbgl/map/transform.cpp

@@ -101,7 +101,7 @@ void Transform::easeTo(const CameraOptions& camera, const AnimationOptions& anim
     double bearing = camera.bearing ? util::deg2rad(-*camera.bearing) : getBearing();
     double pitch = camera.pitch ? util::deg2rad(*camera.pitch) : getPitch();
     double fov = camera.fov ? util::deg2rad(*camera.fov) : getFieldOfView();
-    double alt_m = camera.altM.value_or(100000);
+    double center_alt = camera.centerAltitude.value_or(0);
     double roll = camera.roll ? util::deg2rad(*camera.roll) : getRoll();
 
     if (std::isnan(zoom) || std::isnan(bearing) || std::isnan(pitch)) {
@@ -168,7 +168,7 @@ void Transform::easeTo(const CameraOptions& camera, const AnimationOptions& anim
                 state.setPitch(util::interpolate(startPitch, pitch, t));
             }
             state.setFieldOfView(fov);
-            state.setAltM(alt_m);
+            state.setCenterAltitude(center_alt);
             state.setRoll(roll);
         },
         duration);

src/mbgl/map/transform_state.cpp

@@ -432,7 +432,7 @@ void TransformState::setViewportMode(ViewportMode val) {
 CameraOptions TransformState::getCameraOptions(const std::optional<EdgeInsets>& padding) const {
     return CameraOptions()
         .withCenter(getLatLng())
-        .withAlt(getAltM())
+        .withCenterAltitude(getCenterAltitude())
         .withPadding(padding ? padding : edgeInsets)
         .withZoom(getZoom())
         .withBearing(util::rad2deg(-bearing))
@@ -456,7 +456,7 @@ LatLng TransformState::getLatLng(LatLng::WrapMode wrapMode) const {
     return {util::rad2deg(2 * std::atan(std::exp(y / Cc)) - 0.5 * pi), -x / Bc, wrapMode};
 }
 
-double TransformState::getAltM() const {
+double TransformState::getCenterAltitude() const {
     return z * Projection::getMetersPerPixelAtLatitude(getLatLng().latitude(), getZoom());
 }
 
@@ -838,7 +838,7 @@ void TransformState::setLatLngZoom(const LatLng& latLng, double zoom) {
     setScalePoint(newScale, point);
 }
 
-void TransformState::setAltM(double alt_m) {
+void TransformState::setCenterAltitude(double alt_m) {
     z = alt_m / Projection::getMetersPerPixelAtLatitude(getLatLng().latitude(), getZoom());
     requestMatricesUpdate = true;
 }

src/mbgl/map/transform_state.hpp

@@ -154,7 +154,7 @@ class TransformState {
 
     // Position
     LatLng getLatLng(LatLng::WrapMode = LatLng::Unwrapped) const;
-    double getAltM() const;
+    double getCenterAltitude() const;
     double pixel_x() const;
     double pixel_y() const;
 
@@ -235,7 +235,7 @@ class TransformState {
         point on screen. */
     void moveLatLng(const LatLng&, const ScreenCoordinate&);
     void setLatLngZoom(const LatLng& latLng, double zoom);
-    void setAltM(double alt_m);
+    void setCenterAltitude(double alt_m);
 
     void constrain(double& scale, double& x, double& y) const;
     const mat4& getProjectionMatrix() const;