[core, node] Support axonometric rendering

5 files changed, 75 insertions, 0 deletions

diff --git a/src/mbgl/map/map.cpp b/src/mbgl/map/map.cpp
index 6eb555ad1e..378bd40ab7 100644
--- a/src/mbgl/map/map.cpp
+++ b/src/mbgl/map/map.cpp
@@ -617,6 +617,35 @@ ViewportMode Map::getViewportMode() const {
     return impl->transform.getViewportMode();
 }
 
+#pragma mark - Projection mode
+
+void Map::setAxonometric(bool axonometric) {
+    impl->transform.setAxonometric(axonometric);
+    impl->onUpdate();
+}
+
+bool Map::getAxonometric() const {
+    return impl->transform.getAxonometric();
+}
+
+void Map::setXSkew(double xSkew) {
+    impl->transform.setXSkew(xSkew);
+    impl->onUpdate();
+}
+
+double Map::getXSkew() const {
+    return impl->transform.getXSkew();
+}
+
+void Map::setYSkew(double ySkew) {
+    impl->transform.setYSkew(ySkew);
+    impl->onUpdate();
+}
+
+double Map::getYSkew() const {
+    return impl->transform.getYSkew();
+}
+
 #pragma mark - Projection
 
 ScreenCoordinate Map::pixelForLatLng(const LatLng& latLng) const {
diff --git a/src/mbgl/map/transform.cpp b/src/mbgl/map/transform.cpp
index 2bb25af28f..105adf0400 100644
--- a/src/mbgl/map/transform.cpp
+++ b/src/mbgl/map/transform.cpp
@@ -527,6 +527,32 @@ ViewportMode Transform::getViewportMode() const {
     return state.getViewportMode();
 }
 
+#pragma mark - Projection mode
+
+void Transform::setAxonometric(bool axonometric) {
+    state.axonometric = axonometric;
+}
+
+bool Transform::getAxonometric() const {
+    return state.axonometric;
+}
+
+void Transform::setXSkew(double xSkew) {
+    state.xSkew = xSkew;
+}
+
+double Transform::getXSkew() const {
+    return state.xSkew;
+}
+
+void Transform::setYSkew(double ySkew) {
+    state.ySkew = ySkew;
+}
+
+double Transform::getYSkew() const {
+    return state.ySkew;
+}
+
 #pragma mark - Transition
 
 void Transform::startTransition(const CameraOptions& camera,
diff --git a/src/mbgl/map/transform.hpp b/src/mbgl/map/transform.hpp
index 749228bdf5..d429c57661 100644
--- a/src/mbgl/map/transform.hpp
+++ b/src/mbgl/map/transform.hpp
@@ -125,6 +125,14 @@ public:
     void setViewportMode(ViewportMode);
     ViewportMode getViewportMode() const;
 
+    // Projection mode
+    void setAxonometric(bool);
+    bool getAxonometric() const;
+    void setXSkew(double xSkew);
+    double getXSkew() const;
+    void setYSkew(double ySkew);
+    double getYSkew() const;
+
     // Transitions
     bool inTransition() const;
     void updateTransitions(const TimePoint& now);
diff --git a/src/mbgl/map/transform_state.cpp b/src/mbgl/map/transform_state.cpp
index d1a320beae..d79a65c61e 100644
--- a/src/mbgl/map/transform_state.cpp
+++ b/src/mbgl/map/transform_state.cpp
@@ -66,6 +66,15 @@ void TransformState::getProjMatrix(mat4& projMatrix, uint16_t nearZ) const {
     matrix::translate(projMatrix, projMatrix, pixel_x() - size.width / 2.0f,
                       pixel_y() - size.height / 2.0f, 0);
 
+    if (axonometric) {
+        // mat[11] controls perspective
+        projMatrix[11] = 0;
+
+        // mat[8], mat[9] control x-skew, y-skew
+        projMatrix[8] = xSkew;
+        projMatrix[9] = ySkew;
+    }
+
     matrix::scale(projMatrix, projMatrix, 1, 1,
                   1.0 / Projection::getMetersPerPixelAtLatitude(getLatLng(LatLng::Unwrapped).latitude(), getZoom()));
 }
diff --git a/src/mbgl/map/transform_state.hpp b/src/mbgl/map/transform_state.hpp
index 59522d89fd..0dd6d5a15e 100644
--- a/src/mbgl/map/transform_state.hpp
+++ b/src/mbgl/map/transform_state.hpp
@@ -134,6 +134,9 @@ private:
     // `fov = 2 * arctan((height / 2) / (height * 1.5))`
     double fov = 0.6435011087932844;
     double pitch = 0.0;
+    double xSkew = 0.0;
+    double ySkew = 1.0;
+    bool axonometric = false;
 
     // cache values for spherical mercator math
     double Bc = Projection::worldSize(scale) / util::DEGREES_MAX;