[core, node] Support axonometric rendering

include/mbgl/map/map.hpp

@@ -127,6 +127,14 @@ public:
     void setViewportMode(ViewportMode);
     ViewportMode getViewportMode() const;
 
+    // Projection mode
+    void setAxonometric(bool);
+    bool getAxonometric() const;
+    void setXSkew(double ySkew);
+    double getXSkew() const;
+    void setYSkew(double ySkew);
+    double getYSkew() const;
+
     // Size
     void setSize(Size);
     Size getSize() const;

package.json

@@ -14,7 +14,7 @@
   "license": "BSD-2-Clause",
   "dependencies": {
     "nan": "^2.4.0",
-    "node-pre-gyp": "^0.6.36",
+    "node-pre-gyp": "^0.6.37",
     "npm-run-all": "^4.0.2"
   },
   "devDependencies": {

platform/glfw/settings_json.hpp

@@ -17,6 +17,9 @@ public:
     double zoom = 0;
     double bearing = 0;
     double pitch = 0;
+    bool axonometric = false;
+    double xSkew = 0.0;
+    double ySkew = 1.0;
 
     EnumType debug = 0;
     bool online = true;

platform/node/src/node_map.cpp

@@ -26,6 +26,9 @@ struct NodeMap::RenderOptions {
     double latitude = 0;
     double longitude = 0;
     mbgl::Size size = { 512, 512 };
+    bool axonometric = false;
+    double xSkew = 0;
+    double ySkew = 1;
     std::vector<std::string> classes;
     mbgl::MapDebugOptions debugOptions = mbgl::MapDebugOptions::NoDebug;
 };
@@ -65,6 +68,9 @@ void NodeMap::Init(v8::Local<v8::Object> target) {
     Nan::SetPrototypeMethod(tpl, "setZoom", SetZoom);
     Nan::SetPrototypeMethod(tpl, "setBearing", SetBearing);
     Nan::SetPrototypeMethod(tpl, "setPitch", SetPitch);
+    Nan::SetPrototypeMethod(tpl, "setAxonometric", SetAxonometric);
+    Nan::SetPrototypeMethod(tpl, "setXSkew", SetXSkew);
+    Nan::SetPrototypeMethod(tpl, "setYSkew", SetYSkew);
 
     Nan::SetPrototypeMethod(tpl, "dumpDebugLogs", DumpDebugLogs);
     Nan::SetPrototypeMethod(tpl, "queryRenderedFeatures", QueryRenderedFeatures);
@@ -251,6 +257,19 @@ NodeMap::RenderOptions NodeMap::ParseOptions(v8::Local<v8::Object> obj) {
         options.pitch = Nan::Get(obj, Nan::New("pitch").ToLocalChecked()).ToLocalChecked()->NumberValue();
     }
 
+    if (Nan::Has(obj, Nan::New("axonometric").ToLocalChecked()).FromJust()) {
+        options.axonometric = Nan::Get(obj, Nan::New("axonometric").ToLocalChecked()).ToLocalChecked()->BooleanValue();
+    }
+
+    if (Nan::Has(obj, Nan::New("skew").ToLocalChecked()).FromJust()) {
+        auto skewObj = Nan::Get(obj, Nan::New("skew").ToLocalChecked()).ToLocalChecked();
+        if (skewObj->IsArray()) {
+            auto skew = skewObj.As<v8::Array>();
+            if (skew->Length() > 0) { options.xSkew = Nan::Get(skew, 0).ToLocalChecked()->NumberValue(); }
+            if (skew->Length() > 1) { options.ySkew = Nan::Get(skew, 1).ToLocalChecked()->NumberValue(); }
+        }
+    }
+
     if (Nan::Has(obj, Nan::New("center").ToLocalChecked()).FromJust()) {
         auto centerObj = Nan::Get(obj, Nan::New("center").ToLocalChecked()).ToLocalChecked();
         if (centerObj->IsArray()) {
@@ -370,6 +389,18 @@ void NodeMap::startRender(NodeMap::RenderOptions options) {
     camera.angle = -options.bearing * mbgl::util::DEG2RAD;
     camera.pitch = options.pitch * mbgl::util::DEG2RAD;
 
+    if (map->getAxonometric() != options.axonometric) {
+        map->setAxonometric(options.axonometric);
+    }
+
+    if (map->getXSkew() != options.xSkew) {
+        map->setXSkew(options.xSkew);
+    }
+
+    if (map->getYSkew() != options.ySkew) {
+        map->setYSkew(options.ySkew);
+    }
+
     map->renderStill(camera, options.debugOptions, [this](const std::exception_ptr eptr) {
         if (eptr) {
             error = std::move(eptr);
@@ -879,6 +910,57 @@ void NodeMap::SetPitch(const Nan::FunctionCallbackInfo<v8::Value>& info) {
     info.GetReturnValue().SetUndefined();
 }
 
+void NodeMap::SetAxonometric(const Nan::FunctionCallbackInfo<v8::Value>& info) {
+    auto nodeMap = Nan::ObjectWrap::Unwrap<NodeMap>(info.Holder());
+    if (!nodeMap->map) return Nan::ThrowError(releasedMessage());
+
+    if (info.Length() <= 0 || !info[0]->IsBoolean()) {
+        return Nan::ThrowTypeError("First argument must be a boolean");
+    }
+
+    try {
+        nodeMap->map->setAxonometric(info[0]->BooleanValue());
+    } catch (const std::exception &ex) {
+        return Nan::ThrowError(ex.what());
+    }
+
+    info.GetReturnValue().SetUndefined();
+}
+
+void NodeMap::SetXSkew(const Nan::FunctionCallbackInfo<v8::Value>& info) {
+    auto nodeMap = Nan::ObjectWrap::Unwrap<NodeMap>(info.Holder());
+    if (!nodeMap->map) return Nan::ThrowError(releasedMessage());
+
+    if (info.Length() <= 0 || !info[0]->IsNumber()) {
+        return Nan::ThrowTypeError("First argument must be a number");
+    }
+
+    try {
+        nodeMap->map->setXSkew(info[0]->NumberValue());
+    } catch (const std::exception &ex) {
+        return Nan::ThrowError(ex.what());
+    }
+
+    info.GetReturnValue().SetUndefined();
+}
+
+void NodeMap::SetYSkew(const Nan::FunctionCallbackInfo<v8::Value>& info) {
+    auto nodeMap = Nan::ObjectWrap::Unwrap<NodeMap>(info.Holder());
+    if (!nodeMap->map) return Nan::ThrowError(releasedMessage());
+
+    if (info.Length() <= 0 || !info[0]->IsNumber()) {
+        return Nan::ThrowTypeError("First argument must be a number");
+    }
+
+    try {
+        nodeMap->map->setYSkew(info[0]->NumberValue());
+    } catch (const std::exception &ex) {
+        return Nan::ThrowError(ex.what());
+    }
+
+    info.GetReturnValue().SetUndefined();
+}
+
 void NodeMap::DumpDebugLogs(const Nan::FunctionCallbackInfo<v8::Value>& info) {
     auto nodeMap = Nan::ObjectWrap::Unwrap<NodeMap>(info.Holder());
     if (!nodeMap->map) return Nan::ThrowError(releasedMessage());

platform/node/src/node_map.hpp

@@ -57,6 +57,9 @@ public:
     static void SetZoom(const Nan::FunctionCallbackInfo<v8::Value>&);
     static void SetBearing(const Nan::FunctionCallbackInfo<v8::Value>&);
     static void SetPitch(const Nan::FunctionCallbackInfo<v8::Value>&);
+    static void SetAxonometric(const Nan::FunctionCallbackInfo<v8::Value>&);
+    static void SetXSkew(const Nan::FunctionCallbackInfo<v8::Value>&);
+    static void SetYSkew(const Nan::FunctionCallbackInfo<v8::Value>&);
     static void DumpDebugLogs(const Nan::FunctionCallbackInfo<v8::Value>&);
     static void QueryRenderedFeatures(const Nan::FunctionCallbackInfo<v8::Value>&);
 

platform/node/test/js/map.test.js

@@ -121,6 +121,9 @@ test('Map', function(t) {
             'setZoom',
             'setBearing',
             'setPitch',
+            'setAxonometric',
+            'setXSkew',
+            'setYSkew',
             'dumpDebugLogs',
             'queryRenderedFeatures'
         ]);

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 {

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,

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);

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()));
 }

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;