[core] Compute metersPerPixel from map center point

3 files changed, 7 insertions, 9 deletions

diff --git a/src/mbgl/map/transform_state.cpp b/src/mbgl/map/transform_state.cpp
index d9acecf888..39db23f190 100644
--- a/src/mbgl/map/transform_state.cpp
+++ b/src/mbgl/map/transform_state.cpp
@@ -109,11 +109,12 @@ void TransformState::getProjMatrix(mat4& projMatrix, uint16_t nearZ, bool aligne
     const double furthestDistance = cameraToCenterDistance / (1 - tanMultiple);
     // Add a bit extra to avoid precision problems when a fragment's distance is exactly `furthestDistance`
     const double farZ = furthestDistance * 1.01;
+    double pixelsPerMeter = 1.0 / Projection::getMetersPerPixelAtLatitude(getLatLng().latitude(), getZoom());
 
     // Make sure the camera state is up-to-date
     updateCameraState();
 
-    mat4 worldToCamera = camera.getWorldToCamera(scale, viewportMode == ViewportMode::FlippedY);
+    mat4 worldToCamera = camera.getWorldToCamera(scale, viewportMode == ViewportMode::FlippedY, pixelsPerMeter);
     mat4 cameraToClip =
         camera.getCameraToClipPerspective(getFieldOfView(), double(size.width) / size.height, nearZ, farZ);
 
@@ -139,7 +140,6 @@ void TransformState::getProjMatrix(mat4& projMatrix, uint16_t nearZ, bool aligne
         projMatrix[11] = 0.0;
 
         // mat[8], mat[9] control x-skew, y-skew
-        double pixelsPerMeter = 1.0 / Projection::getMetersPerPixelAtLatitude(getLatLng().latitude(), getZoom());
         projMatrix[8] = xSkew * pixelsPerMeter;
         projMatrix[9] = ySkew * pixelsPerMeter;
     }
diff --git a/src/mbgl/util/camera.cpp b/src/mbgl/util/camera.cpp
index 34d27620ac..c910c05ca8 100644
--- a/src/mbgl/util/camera.cpp
+++ b/src/mbgl/util/camera.cpp
@@ -97,13 +97,13 @@ vec3 Camera::getPosition() const {
     return {{p[0], p[1], p[2]}};
 }
 
-mat4 Camera::getCameraToWorld(double scale, bool flippedY) const {
+mat4 Camera::getCameraToWorld(double scale, bool flippedY, double pixelsPerMeter) const {
     mat4 cameraToWorld;
-    matrix::invert(cameraToWorld, getWorldToCamera(scale, flippedY));
+    matrix::invert(cameraToWorld, getWorldToCamera(scale, flippedY, pixelsPerMeter));
     return cameraToWorld;
 }
 
-mat4 Camera::getWorldToCamera(double scale, bool flippedY) const {
+mat4 Camera::getWorldToCamera(double scale, bool flippedY, double pixelsPerMeter) const {
     // transformation chain from world space to camera space:
     // 1. Height value (z) of renderables is in meters. Scale z coordinate by pixelsPerMeter
     // 2. Transform from pixel coordinates to camera space with cameraMatrix^-1
@@ -112,8 +112,6 @@ mat4 Camera::getWorldToCamera(double scale, bool flippedY) const {
     // worldToCamera: flip * cam^-1 * zScale
     // cameraToWorld: (flip * cam^-1 * zScale)^-1 => (zScale^-1 * cam * flip^-1)
     const double worldSize = Projection::worldSize(scale);
-    const double latitude = latFromMercatorY(getColumn(transform, 3)[1]);
-    const double pixelsPerMeter = worldSize / (std::cos(latitude * util::DEG2RAD) * util::M2PI * util::EARTH_RADIUS_M);
 
     // Compute inverse of the camera matrix
     mat4 result = orientation.conjugate().toRotationMatrix();
diff --git a/src/mbgl/util/camera.hpp b/src/mbgl/util/camera.hpp
index 030d7cfaac..d0781832a4 100644
--- a/src/mbgl/util/camera.hpp
+++ b/src/mbgl/util/camera.hpp
@@ -15,8 +15,8 @@ public:
     Camera();
 
     vec3 getPosition() const;
-    mat4 getCameraToWorld(double scale, bool flippedY) const;
-    mat4 getWorldToCamera(double scale, bool flippedY) const;
+    mat4 getCameraToWorld(double scale, bool flippedY, double pixelsPerMeter) const;
+    mat4 getWorldToCamera(double scale, bool flippedY, double pixelsPerMeter) const;
     mat4 getCameraToClipPerspective(double fovy, double aspectRatio, double nearZ, double farZ) const;
 
     vec3 forward() const;