Add an option to display areas of closed contours.

This is useful e.g. for architectural work.

CHANGELOG.md

@@ -49,6 +49,7 @@ New measurement/analysis features:
     "Analyze → Measure Perimeter".
   * New command for measuring center of mass, with live updates as the sketch
     changes, "Analyze → Center of Mass".
+  * New option for displaying areas of closed contours.
   * When selecting a point and a line, projected distance to to current
     workplane is displayed.
 

src/confscreen.cpp

@@ -84,6 +84,11 @@ void TextWindow::ScreenChangeBackFaces(int link, uint32_t v) {
     InvalidateGraphics();
 }
 
+void TextWindow::ScreenChangeShowContourAreas(int link, uint32_t v) {
+    SS.showContourAreas = !SS.showContourAreas;
+    InvalidateGraphics();
+}
+
 void TextWindow::ScreenChangeCheckClosedContour(int link, uint32_t v) {
     SS.checkClosedContour = !SS.checkClosedContour;
     InvalidateGraphics();
@@ -297,6 +302,9 @@ void TextWindow::ShowConfiguration() {
     Printf(false, "  %Fd%f%Ll%s  check sketch for closed contour%E",
         &ScreenChangeCheckClosedContour,
         SS.checkClosedContour ? CHECK_TRUE : CHECK_FALSE);
+    Printf(false, "  %Fd%f%Ll%s  show areas of closed contours%E",
+        &ScreenChangeShowContourAreas,
+        SS.showContourAreas ? CHECK_TRUE : CHECK_FALSE);
 
     Printf(false, "");
     Printf(false, "%Ft autosave interval (in minutes)%E");

src/draw.cpp

@@ -693,6 +693,16 @@ void GraphicsWindow::Draw(Canvas *canvas) {
         c.Draw(Constraint::DrawAs::DEFAULT, canvas);
     }
 
+    // Draw areas
+    if(SS.showContourAreas) {
+        for(hGroup hg : SK.groupOrder) {
+            Group *g = SK.GetGroup(hg);
+            if(g->h.v != activeGroup.v) continue;
+            if(!(g->IsVisible())) continue;
+            g->DrawContourAreaLabels(canvas);
+        }
+    }
+
     // Draw the "pending" constraint, i.e. a constraint that would be
     // placed on a line that is almost horizontal or vertical.
     if(SS.GW.pending.operation == Pending::DRAGGING_NEW_LINE_POINT &&

src/groupmesh.cpp

@@ -677,3 +677,38 @@ void Group::DrawFilledPaths(Canvas *canvas) {
     }
 }
 
+void Group::DrawContourAreaLabels(Canvas *canvas) {
+    const Camera &camera = canvas->GetCamera();
+    Vector gr = camera.projRight.ScaledBy(1 / camera.scale);
+    Vector gu = camera.projUp.ScaledBy(1 / camera.scale);
+
+    for(SBezierLoopSet &sbls : bezierLoops.l) {
+        if(sbls.l.n == 0 || sbls.l.elem[0].l.n == 0) continue;
+
+        Vector min = sbls.l.elem[0].l.elem[0].ctrl[0];
+        Vector max = min;
+        Vector zero = Vector::From(0.0, 0.0, 0.0);
+        sbls.GetBoundingProjd(Vector::From(1.0, 0.0, 0.0), zero, &min.x, &max.x);
+        sbls.GetBoundingProjd(Vector::From(0.0, 1.0, 0.0), zero, &min.y, &max.y);
+        sbls.GetBoundingProjd(Vector::From(0.0, 0.0, 1.0), zero, &min.z, &max.z);
+
+        Vector mid = min.Plus(max).ScaledBy(0.5);
+
+        hStyle hs = { Style::CONSTRAINT };
+        Canvas::Stroke stroke = Style::Stroke(hs);
+        stroke.layer = Canvas::Layer::FRONT;
+
+        double scale = SS.MmPerUnit();
+        std::string label = ssprintf("%.3f %s²",
+                                     fabs(sbls.SignedArea() / (scale * scale)),
+                                     SS.UnitName());
+
+        double fontHeight = Style::TextHeight(hs);
+        double textWidth  = VectorFont::Builtin()->GetWidth(fontHeight, label),
+               textHeight = VectorFont::Builtin()->GetCapHeight(fontHeight);
+        Vector pos = mid.Minus(gr.ScaledBy(textWidth / 2.0))
+                        .Minus(gu.ScaledBy(textHeight / 2.0));
+        canvas->DrawVectorText(label, fontHeight, pos, gr, gu, canvas->GetStroke(stroke));
+    }
+}
+

src/sketch.h

@@ -287,6 +287,7 @@ public:
     void Draw(Canvas *canvas);
     void DrawPolyError(Canvas *canvas);
     void DrawFilledPaths(Canvas *canvas);
+    void DrawContourAreaLabels(Canvas *canvas);
 
     SPolygon GetPolygon();
 

src/solvespace.cpp

@@ -70,6 +70,8 @@ void SolveSpaceUI::Init() {
     drawBackFaces = CnfThawBool(true, "DrawBackFaces");
     // Check that contours are closed and not self-intersecting
     checkClosedContour = CnfThawBool(true, "CheckClosedContour");
+    // Draw closed polygons areas
+    showContourAreas = CnfThawBool(false, "ShowContourAreas");
     // Export shaded triangles in a 2d view
     exportShadedTriangles = CnfThawBool(true, "ExportShadedTriangles");
     // Export pwl curves (instead of exact) always
@@ -191,6 +193,8 @@ void SolveSpaceUI::Exit() {
     CnfFreezeBool(fixExportColors, "FixExportColors");
     // Draw back faces of triangles (when mesh is leaky/self-intersecting)
     CnfFreezeBool(drawBackFaces, "DrawBackFaces");
+    // Draw closed polygons areas
+    CnfFreezeBool(showContourAreas, "ShowContourAreas");
     // Check that contours are closed and not self-intersecting
     CnfFreezeBool(checkClosedContour, "CheckClosedContour");
     // Export shaded triangles in a 2d view

src/solvespace.h

@@ -651,6 +651,7 @@ public:
     float    exportOffset;
     bool     fixExportColors;
     bool     drawBackFaces;
+    bool     showContourAreas;
     bool     checkClosedContour;
     bool     showToolbar;
     Platform::Path screenshotFile;

src/srf/curve.cpp

@@ -536,6 +536,17 @@ void SBezierLoopSet::GetBoundingProjd(Vector u, Vector orig,
     }
 }
 
+double SBezierLoopSet::SignedArea() {
+    if(EXACT(area == 0.0)) {
+        SPolygon sp = {};
+        MakePwlInto(&sp);
+        sp.normal = sp.ComputeNormal();
+        area = sp.SignedArea();
+        sp.Clear();
+    }
+    return area;
+}
+
 //-----------------------------------------------------------------------------
 // Convert all the Beziers into piecewise linear form, and assemble that into
 // a polygon, one contour per loop.

src/srf/surface.h

@@ -151,6 +151,7 @@ public:
     List<SBezierLoop> l;
     Vector normal;
     Vector point;
+    double area;
 
     static SBezierLoopSet From(SBezierList *spcl, SPolygon *poly,
                                double chordTol,
@@ -158,6 +159,7 @@ public:
                                SBezierList *openContours);
 
     void GetBoundingProjd(Vector u, Vector orig, double *umin, double *umax) const;
+    double SignedArea();
     void MakePwlInto(SPolygon *sp) const;
     void Clear();
 };

src/ui.h

@@ -517,6 +517,7 @@ public:
 
     static void ScreenChangeFixExportColors(int link, uint32_t v);
     static void ScreenChangeBackFaces(int link, uint32_t v);
+    static void ScreenChangeShowContourAreas(int link, uint32_t v);
     static void ScreenChangeCheckClosedContour(int link, uint32_t v);
     static void ScreenChangePwlCurves(int link, uint32_t v);
     static void ScreenChangeCanvasSizeAuto(int link, uint32_t v);

test/CMakeLists.txt

@@ -11,6 +11,7 @@ endforeach()
 
 set(testsuite_SOURCES
     harness.cpp
+    analysis/contour_area/test.cpp
     core/expr/test.cpp
     core/locale/test.cpp
     core/path/test.cpp

test/analysis/contour_area/test.cpp

@@ -0,0 +1,7 @@
+#include "harness.h"
+
+TEST_CASE(normal_roundtrip) {
+    SS.showContourAreas = true;
+    CHECK_LOAD("normal.slvs");
+    CHECK_RENDER("normal.png");
+}