[core] Implement circle-pitch-alignment property

Closes issue #9349.

7 files changed, 67 insertions, 12 deletions

diff --git a/src/mbgl/programs/circle_program.hpp b/src/mbgl/programs/circle_program.hpp
index 8f056048b1..3590acbeef 100644
--- a/src/mbgl/programs/circle_program.hpp
+++ b/src/mbgl/programs/circle_program.hpp
@@ -21,7 +21,9 @@ class CircleProgram : public Program<
     gl::Uniforms<
         uniforms::u_matrix,
         uniforms::u_scale_with_map,
-        uniforms::u_extrude_scale>,
+        uniforms::u_extrude_scale,
+        uniforms::u_camera_to_center_distance,
+        uniforms::u_pitch_with_map>,
     style::CirclePaintProperties>
 {
 public:
diff --git a/src/mbgl/programs/symbol_program.hpp b/src/mbgl/programs/symbol_program.hpp
index e7c428034b..c11e0b5ca1 100644
--- a/src/mbgl/programs/symbol_program.hpp
+++ b/src/mbgl/programs/symbol_program.hpp
@@ -30,7 +30,6 @@ class TransformState;
 
 namespace uniforms {
 MBGL_DEFINE_UNIFORM_SCALAR(bool, u_rotate_with_map);
-MBGL_DEFINE_UNIFORM_SCALAR(bool, u_pitch_with_map);
 MBGL_DEFINE_UNIFORM_SCALAR(gl::TextureUnit, u_texture);
 MBGL_DEFINE_UNIFORM_SCALAR(gl::TextureUnit, u_fadetexture);
 MBGL_DEFINE_UNIFORM_SCALAR(float, u_aspect_ratio);
diff --git a/src/mbgl/programs/uniforms.hpp b/src/mbgl/programs/uniforms.hpp
index f1b2c2fb54..c8f8684ba1 100644
--- a/src/mbgl/programs/uniforms.hpp
+++ b/src/mbgl/programs/uniforms.hpp
@@ -33,6 +33,8 @@ MBGL_DEFINE_UNIFORM_SCALAR(float, u_gapwidth);
 MBGL_DEFINE_UNIFORM_SCALAR(float, u_offset);
 MBGL_DEFINE_UNIFORM_SCALAR(Size, u_world);
 MBGL_DEFINE_UNIFORM_SCALAR(Size, u_texsize);
+MBGL_DEFINE_UNIFORM_SCALAR(bool, u_pitch_with_map);
+MBGL_DEFINE_UNIFORM_SCALAR(float, u_camera_to_center_distance);
 
 MBGL_DEFINE_UNIFORM_VECTOR(float, 2, u_extrude_scale);
 
diff --git a/src/mbgl/renderer/painters/painter_circle.cpp b/src/mbgl/renderer/painters/painter_circle.cpp
index 58e384979d..a077f557fc 100644
--- a/src/mbgl/renderer/painters/painter_circle.cpp
+++ b/src/mbgl/renderer/painters/painter_circle.cpp
@@ -22,6 +22,7 @@ void Painter::renderCircle(PaintParameters& parameters,
 
     const CirclePaintProperties::PossiblyEvaluated& properties = layer.evaluated;
     const bool scaleWithMap = properties.get<CirclePitchScale>() == CirclePitchScaleType::Map;
+    const bool pitchWithMap = properties.get<CirclePitchAlignment>() == AlignmentType::Map;
 
     parameters.programs.circle.get(properties).draw(
         context,
@@ -38,12 +39,13 @@ void Painter::renderCircle(PaintParameters& parameters,
                                       state)
             },
             uniforms::u_scale_with_map::Value{ scaleWithMap },
-            uniforms::u_extrude_scale::Value{ scaleWithMap
+            uniforms::u_extrude_scale::Value{ pitchWithMap
                 ? std::array<float, 2> {{
-                    pixelsToGLUnits[0] * state.getCameraToCenterDistance(),
-                    pixelsToGLUnits[1] * state.getCameraToCenterDistance()
-                  }}
-                : pixelsToGLUnits }
+                    tile.id.pixelsToTileUnits(1, state.getZoom()),
+                    tile.id.pixelsToTileUnits(1, state.getZoom()) }}
+                : pixelsToGLUnits },
+            uniforms::u_camera_to_center_distance::Value{ state.getCameraToCenterDistance() },
+            uniforms::u_pitch_with_map::Value{ pitchWithMap }
         },
         *bucket.vertexBuffer,
         *bucket.indexBuffer,
diff --git a/src/mbgl/shaders/circle.cpp b/src/mbgl/shaders/circle.cpp
index 2e0c76122c..953e750776 100644
--- a/src/mbgl/shaders/circle.cpp
+++ b/src/mbgl/shaders/circle.cpp
@@ -9,7 +9,9 @@ const char* circle::name = "circle";
 const char* circle::vertexSource = R"MBGL_SHADER(
 uniform mat4 u_matrix;
 uniform bool u_scale_with_map;
+uniform bool u_pitch_with_map;
 uniform vec2 u_extrude_scale;
+uniform highp float u_camera_to_center_distance;
 
 attribute vec2 a_pos;
 
@@ -121,12 +123,28 @@ void main(void) {
 
     // multiply a_pos by 0.5, since we had it * 2 in order to sneak
     // in extrusion data
-    gl_Position = u_matrix * vec4(floor(a_pos * 0.5), 0, 1);
-
-    if (u_scale_with_map) {
-        gl_Position.xy += extrude * (radius + stroke_width) * u_extrude_scale;
+    vec2 circle_center = floor(a_pos * 0.5);
+    if (u_pitch_with_map) {
+        vec2 corner_position = circle_center;
+        if (u_scale_with_map) {
+            corner_position += extrude * (radius + stroke_width) * u_extrude_scale;
+        } else {
+            // Pitching the circle with the map effectively scales it with the map
+            // To counteract the effect for pitch-scale: viewport, we rescale the
+            // whole circle based on the pitch scaling effect at its central point
+            vec4 projected_center = u_matrix * vec4(circle_center, 0, 1);
+            corner_position += extrude * (radius + stroke_width) * u_extrude_scale * (projected_center.w / u_camera_to_center_distance);
+        }
+
+        gl_Position = u_matrix * vec4(corner_position, 0, 1);
     } else {
-        gl_Position.xy += extrude * (radius + stroke_width) * u_extrude_scale * gl_Position.w;
+        gl_Position = u_matrix * vec4(circle_center, 0, 1);
+
+        if (u_scale_with_map) {
+            gl_Position.xy += extrude * (radius + stroke_width) * u_extrude_scale * u_camera_to_center_distance;
+        } else {
+            gl_Position.xy += extrude * (radius + stroke_width) * u_extrude_scale * gl_Position.w;
+        }
     }
 
     // This is a minimum blur distance that serves as a faux-antialiasing for
diff --git a/src/mbgl/style/layers/circle_layer.cpp b/src/mbgl/style/layers/circle_layer.cpp
index 3bba135c84..9854932699 100644
--- a/src/mbgl/style/layers/circle_layer.cpp
+++ b/src/mbgl/style/layers/circle_layer.cpp
@@ -283,6 +283,33 @@ TransitionOptions CircleLayer::getCirclePitchScaleTransition() const {
     return impl().paint.template get<CirclePitchScale>().options;
 }
 
+PropertyValue<AlignmentType> CircleLayer::getDefaultCirclePitchAlignment() {
+    return { AlignmentType::Viewport };
+}
+
+PropertyValue<AlignmentType> CircleLayer::getCirclePitchAlignment() const {
+    return impl().paint.template get<CirclePitchAlignment>().value;
+}
+
+void CircleLayer::setCirclePitchAlignment(PropertyValue<AlignmentType> value) {
+    if (value == getCirclePitchAlignment())
+        return;
+    auto impl_ = mutableImpl();
+    impl_->paint.template get<CirclePitchAlignment>().value = value;
+    baseImpl = std::move(impl_);
+    observer->onLayerChanged(*this);
+}
+
+void CircleLayer::setCirclePitchAlignmentTransition(const TransitionOptions& options) {
+    auto impl_ = mutableImpl();
+    impl_->paint.template get<CirclePitchAlignment>().options = options;
+    baseImpl = std::move(impl_);
+}
+
+TransitionOptions CircleLayer::getCirclePitchAlignmentTransition() const {
+    return impl().paint.template get<CirclePitchAlignment>().options;
+}
+
 DataDrivenPropertyValue<float> CircleLayer::getDefaultCircleStrokeWidth() {
     return { 0 };
 }
diff --git a/src/mbgl/style/layers/circle_layer_properties.hpp b/src/mbgl/style/layers/circle_layer_properties.hpp
index 73b7028465..bc0c961e75 100644
--- a/src/mbgl/style/layers/circle_layer_properties.hpp
+++ b/src/mbgl/style/layers/circle_layer_properties.hpp
@@ -40,6 +40,10 @@ struct CirclePitchScale : PaintProperty<CirclePitchScaleType> {
     static CirclePitchScaleType defaultValue() { return CirclePitchScaleType::Map; }
 };
 
+struct CirclePitchAlignment : PaintProperty<AlignmentType> {
+    static AlignmentType defaultValue() { return AlignmentType::Viewport; }
+};
+
 struct CircleStrokeWidth : DataDrivenPaintProperty<float, attributes::a_stroke_width, uniforms::u_stroke_width> {
     static float defaultValue() { return 0; }
 };
@@ -60,6 +64,7 @@ class CirclePaintProperties : public Properties<
     CircleTranslate,
     CircleTranslateAnchor,
     CirclePitchScale,
+    CirclePitchAlignment,
     CircleStrokeWidth,
     CircleStrokeColor,
     CircleStrokeOpacity