[core] Make extrudeScale calculations more similar to JS

4 files changed, 28 insertions, 20 deletions

diff --git a/src/mbgl/renderer/painter.cpp b/src/mbgl/renderer/painter.cpp
index ba68b5a24d..d6f14708aa 100644
--- a/src/mbgl/renderer/painter.cpp
+++ b/src/mbgl/renderer/painter.cpp
@@ -114,10 +114,10 @@ void Painter::render(const Style& style, const FrameData& frame_, SpriteAtlas& a
     // Update the default matrices to the current viewport dimensions.
     state.getProjMatrix(projMatrix);
 
-    // The extrusion scale.
-    const float flippedY = state.getViewportMode() == ViewportMode::FlippedY;
-    extrudeScale = {{ 2.0f / state.getWidth() * state.getAltitude(),
-                      (flippedY ? 2.0f : -2.0f) / state.getHeight() * state.getAltitude() }};
+    pixelsToGLUnits = {{ 2.0f  / state.getWidth(), -2.0f / state.getHeight() }};
+    if (state.getViewportMode() == ViewportMode::FlippedY) {
+        pixelsToGLUnits[1] *= -1;
+    }
 
     // The native matrix is a 1:1 matrix that paints the coordinates at the
     // same screen position as the vertex specifies.
diff --git a/src/mbgl/renderer/painter.hpp b/src/mbgl/renderer/painter.hpp
index 03885ed49e..5e8831b239 100644
--- a/src/mbgl/renderer/painter.hpp
+++ b/src/mbgl/renderer/painter.hpp
@@ -159,7 +159,7 @@ private:
     mat4 projMatrix;
     mat4 nativeMatrix;
 
-    std::array<float, 2> extrudeScale;
+    std::array<float, 2> pixelsToGLUnits;
 
     // used to composite images and flips the geometry upside down
     const mat4 flipMatrix = []{
diff --git a/src/mbgl/renderer/painter_circle.cpp b/src/mbgl/renderer/painter_circle.cpp
index e36019463a..5bc31f7f81 100644
--- a/src/mbgl/renderer/painter_circle.cpp
+++ b/src/mbgl/renderer/painter_circle.cpp
@@ -32,7 +32,10 @@ void Painter::renderCircle(CircleBucket& bucket,
     config.program = circleShader.getID();
 
     circleShader.u_matrix = vtxMatrix;
-    circleShader.u_extrude_scale = extrudeScale;
+    circleShader->u_extrude_scale = {{
+        pixelsToGLUnits[0] * state.getAltitude(),
+        pixelsToGLUnits[1] * state.getAltitude()
+    }};
     circleShader.u_devicepixelratio = frame.pixelRatio;
     circleShader.u_color = properties.circleColor;
     circleShader.u_radius = properties.circleRadius;
diff --git a/src/mbgl/renderer/painter_symbol.cpp b/src/mbgl/renderer/painter_symbol.cpp
index 4559b02778..8b4138819c 100644
--- a/src/mbgl/renderer/painter_symbol.cpp
+++ b/src/mbgl/renderer/painter_symbol.cpp
@@ -44,23 +44,26 @@ void Painter::renderSDF(SymbolBucket &bucket,
     float fontSize = paintSize;
     float fontScale = fontSize / sdfFontSize;
 
-    float scale = fontScale;
-    std::array<float, 2> exScale = extrudeScale;
     bool rotateWithMap = rotationAlignment == AlignmentType::Map;
     bool pitchWithMap = pitchAlignment == AlignmentType::Map;
-    float gammaScale = 1.0f;
+
+    std::array<float, 2> extrudeScale;
+    float gammaScale;
 
     if (pitchWithMap) {
-        scale *= tileID.pixelsToTileUnits(1, state.getZoom());
-        exScale.fill(scale);
-        gammaScale /= std::cos(state.getPitch());
+        gammaScale = 1.0 / std::cos(state.getPitch());
+        extrudeScale.fill(tileID.pixelsToTileUnits(1, state.getZoom()) * fontScale);
     } else {
-        exScale = {{ exScale[0] * scale, exScale[1] * scale }};
+        gammaScale = 1.0;
+        extrudeScale = {{
+            pixelsToGLUnits[0] * fontScale * state.getAltitude(),
+            pixelsToGLUnits[1] * fontScale * state.getAltitude()
+        }};
     }
 
     config.program = sdfShader.getID();
     sdfShader.u_matrix = vtxMatrix;
-    sdfShader.u_extrude_scale = exScale;
+    sdfShader.u_extrude_scale = extrudeScale;
     sdfShader.u_texsize = texsize;
     sdfShader.u_rotate_with_map = rotateWithMap;
     sdfShader.u_pitch_with_map = pitchWithMap;
@@ -189,14 +192,16 @@ void Painter::renderSymbol(SymbolBucket& bucket,
             mat4 vtxMatrix =
                 translatedMatrix(matrix, paint.iconTranslate, tileID, paint.iconTranslateAnchor);
 
-            float scale = fontScale;
-            std::array<float, 2> exScale = extrudeScale;
+            std::array<float, 2> extrudeScale;
+
             const bool alignedWithMap = layout.iconRotationAlignment == AlignmentType::Map;
             if (alignedWithMap) {
-                scale *= tileID.pixelsToTileUnits(1, state.getZoom());
-                exScale.fill(scale);
+                extrudeScale.fill(tileID.pixelsToTileUnits(1, state.getZoom()) * fontScale);
             } else {
-                exScale = {{ exScale[0] * scale, exScale[1] * scale }};
+                extrudeScale = {{
+                    pixelsToGLUnits[0] * fontScale * state.getAltitude(),
+                    pixelsToGLUnits[1] * fontScale * state.getAltitude()
+                }};
             }
 
             const bool overdraw = isOverdraw();
@@ -204,7 +209,7 @@ void Painter::renderSymbol(SymbolBucket& bucket,
 
             config.program = iconShader.getID();
             iconShader.u_matrix = vtxMatrix;
-            iconShader.u_extrude_scale = exScale;
+            iconShader.u_extrude_scale = extrudeScale;
             iconShader.u_texsize = {{ float(activeSpriteAtlas->getWidth()) / 4.0f, float(activeSpriteAtlas->getHeight()) / 4.0f }};
             iconShader.u_rotate_with_map = alignedWithMap;
             iconShader.u_texture = 0;