Initial implementation of polygon trianagulation. It seems to be robust and passes the associated tests,
but has some problems:
(1) it generates T-vertices;
(2) it only works with right-handed outer contours;
(3) The sort and search are inefficient.
git-svn-id: http://skia.googlecode.com/svn/trunk@119 2bbb7eff-a529-9590-31e7-b0007b416f81
diff --git a/tests/TriangulationTest.cpp b/tests/TriangulationTest.cpp
new file mode 100644
index 0000000..869e739
--- /dev/null
+++ b/tests/TriangulationTest.cpp
@@ -0,0 +1,292 @@
+#include "Test.h"
+#include "../../src/core/SkConcaveToTriangles.h"
+#include "SkGeometry.h"
+
+static int GetIndexFromPoint(const SkPoint &pt,
+ int numPts, const SkPoint *pts) {
+ for (int i = 0; i < numPts; ++i)
+ if (pt.fX == pts[i].fX && pt.fY == pts[i].fY)
+ return i;
+ return -1;
+}
+
+
+bool gPrintTriangles = false; // Can we set this on the command line?
+
+static void PrintTriangles(const SkTDArray<SkPoint> &triangles,
+ int numPts, const SkPoint *pts,
+ skiatest::Reporter* reporter) {
+ if (gPrintTriangles) {
+ SkPoint *p = triangles.begin();
+ int n = triangles.count();
+ REPORTER_ASSERT(reporter, n % 3 == 0);
+ n /= 3;
+ printf("%d Triangles:\n{\n", n);
+ for (; n-- != 0; p += 3)
+ printf(" { {%.7g, %.7g}, {%.7g, %.7g}, {%.7g, %.7g} }, "
+ "// { %2d, %2d, %2d }\n",
+ p[0].fX, p[0].fY,
+ p[1].fX, p[1].fY,
+ p[2].fX, p[2].fY,
+ GetIndexFromPoint(p[0], numPts, pts),
+ GetIndexFromPoint(p[1], numPts, pts),
+ GetIndexFromPoint(p[2], numPts, pts));
+ printf("}\n");
+ }
+}
+
+
+static bool CompareTriangleList(size_t numTriangles,
+ const float refTriangles[][3][2],
+ const SkTDArray<SkPoint> &triangles) {
+ if (triangles.count() != numTriangles * 3) {
+ printf("Expected %d triangles, not %d\n",
+ numTriangles, triangles.count() / 3);
+ return false;
+ }
+ size_t numErrors = 0;
+ for (size_t i = 0; i < numTriangles; ++i) {
+ const float *r = &refTriangles[i][0][0];
+ const SkScalar *t = &triangles[i * 3].fX;
+ bool equalTriangle = true;
+ for (int j = 6; j-- != 0; r++, t++)
+ if (SkFloatToScalar(*r) != *t)
+ equalTriangle = false;
+ if (equalTriangle == false) {
+ ++numErrors;
+ printf("Triangle %d differs\n", i);
+ }
+ }
+ if (numErrors > 0)
+ printf("%d triangles differ\n", numErrors);
+ return numErrors == 0;
+}
+
+
+#ifndef LEFT_HANDED_POLYGONS
+static const SkPoint star[] = {
+ // Outer contour is clockwise if Y is down, counterclockwise if Y is up.
+ { SkFloatToScalar(110), SkFloatToScalar( 20) },
+ { SkFloatToScalar(100), SkFloatToScalar( 50) },
+ { SkFloatToScalar(130), SkFloatToScalar( 80) },
+ { SkFloatToScalar( 90), SkFloatToScalar( 80) },
+ { SkFloatToScalar( 70), SkFloatToScalar(120) },
+ { SkFloatToScalar( 50), SkFloatToScalar( 80) },
+ { SkFloatToScalar( 10), SkFloatToScalar( 80) },
+ { SkFloatToScalar( 40), SkFloatToScalar( 50) },
+ { SkFloatToScalar( 30), SkFloatToScalar( 20) },
+ { SkFloatToScalar( 70), SkFloatToScalar( 40) },
+ // Inner contour is counterclockwise if Y is down, clockwise if Y is up.
+ { SkFloatToScalar(110), SkFloatToScalar( 20) },
+ { SkFloatToScalar( 70), SkFloatToScalar( 50) },
+ { SkFloatToScalar( 60), SkFloatToScalar( 60) },
+ { SkFloatToScalar( 60), SkFloatToScalar( 70) },
+ { SkFloatToScalar( 80), SkFloatToScalar( 70) },
+ { SkFloatToScalar( 80), SkFloatToScalar( 60) },
+ { SkFloatToScalar( 70), SkFloatToScalar( 50) }
+};
+static const SkPoint plus[] = {
+ { SkFloatToScalar( 70), SkFloatToScalar( 10) },
+ { SkFloatToScalar( 70), SkFloatToScalar( 50) },
+ { SkFloatToScalar(110), SkFloatToScalar( 50) },
+ { SkFloatToScalar(110), SkFloatToScalar( 70) },
+ { SkFloatToScalar( 70), SkFloatToScalar( 70) },
+ { SkFloatToScalar( 70), SkFloatToScalar(110) },
+ { SkFloatToScalar( 50), SkFloatToScalar(110) },
+ { SkFloatToScalar( 50), SkFloatToScalar( 70) },
+ { SkFloatToScalar( 10), SkFloatToScalar( 70) },
+ { SkFloatToScalar( 10), SkFloatToScalar( 50) },
+ { SkFloatToScalar( 50), SkFloatToScalar( 50) },
+ { SkFloatToScalar( 50), SkFloatToScalar( 10) }
+};
+static const SkPoint zipper[] = {
+ { SkFloatToScalar( 10), SkFloatToScalar( 60) },
+ { SkFloatToScalar( 10), SkFloatToScalar( 10) },
+ { SkFloatToScalar( 20), SkFloatToScalar( 10) },
+ { SkFloatToScalar( 20), SkFloatToScalar( 50) },
+ { SkFloatToScalar( 30), SkFloatToScalar( 50) },
+ { SkFloatToScalar( 30), SkFloatToScalar( 10) },
+ { SkFloatToScalar( 60), SkFloatToScalar( 10) },
+ { SkFloatToScalar( 60), SkFloatToScalar( 50) },
+ { SkFloatToScalar( 70), SkFloatToScalar( 50) },
+ { SkFloatToScalar( 70), SkFloatToScalar( 10) },
+ { SkFloatToScalar(100), SkFloatToScalar( 10) },
+ { SkFloatToScalar(100), SkFloatToScalar( 50) },
+ { SkFloatToScalar(110), SkFloatToScalar( 50) },
+ { SkFloatToScalar(110), SkFloatToScalar( 10) },
+ { SkFloatToScalar(140), SkFloatToScalar( 10) },
+ { SkFloatToScalar(140), SkFloatToScalar( 60) },
+ { SkFloatToScalar(130), SkFloatToScalar( 60) },
+ { SkFloatToScalar(130), SkFloatToScalar( 20) },
+ { SkFloatToScalar(120), SkFloatToScalar( 20) },
+ { SkFloatToScalar(120), SkFloatToScalar( 60) },
+ { SkFloatToScalar( 90), SkFloatToScalar( 60) },
+ { SkFloatToScalar( 90), SkFloatToScalar( 20) },
+ { SkFloatToScalar( 80), SkFloatToScalar( 20) },
+ { SkFloatToScalar( 80), SkFloatToScalar( 60) },
+ { SkFloatToScalar( 50), SkFloatToScalar( 60) },
+ { SkFloatToScalar( 50), SkFloatToScalar( 20) },
+ { SkFloatToScalar( 40), SkFloatToScalar( 20) },
+ { SkFloatToScalar( 40), SkFloatToScalar( 60) }
+};
+#else // LEFT_HANDED_POLYGONS
+static const SkPoint star[] = {
+ // Outer contour is counterclockwise if Y is down, clockwise if Y is up.
+ { SkFloatToScalar(110), SkFloatToScalar( 20) },
+ { SkFloatToScalar( 70), SkFloatToScalar( 40) },
+ { SkFloatToScalar( 30), SkFloatToScalar( 20) },
+ { SkFloatToScalar( 40), SkFloatToScalar( 50) },
+ { SkFloatToScalar( 10), SkFloatToScalar( 80) },
+ { SkFloatToScalar( 50), SkFloatToScalar( 80) },
+ { SkFloatToScalar( 70), SkFloatToScalar(120) },
+ { SkFloatToScalar( 90), SkFloatToScalar( 80) },
+ { SkFloatToScalar(130), SkFloatToScalar( 80) },
+ { SkFloatToScalar(100), SkFloatToScalar( 50) },
+ // Inner contour is clockwise if Y is down, counterclockwise if Y is up.
+ { SkFloatToScalar(110), SkFloatToScalar( 20) },
+ { SkFloatToScalar( 70), SkFloatToScalar( 50) },
+ { SkFloatToScalar( 80), SkFloatToScalar( 60) },
+ { SkFloatToScalar( 80), SkFloatToScalar( 70) },
+ { SkFloatToScalar( 60), SkFloatToScalar( 70) },
+ { SkFloatToScalar( 60), SkFloatToScalar( 60) },
+ { SkFloatToScalar( 70), SkFloatToScalar( 50) }
+};
+#endif // LEFT_HANDED_POLYGONS
+#define kNumStarVertices 10
+#define kNumStarHoleVertices (sizeof(star) / sizeof(star[0]))
+
+
+// Star test
+static void TestStarTriangulation(skiatest::Reporter* reporter) {
+ static const float refTriangles[][3][2] = {
+ { { 30, 20}, { 70, 40}, { 40, 50} }, // { 8, 9, 7 }
+ { {100, 50}, { 10, 80}, { 40, 50} }, // { 1, 6, 7 }
+ { {100, 50}, { 40, 50}, { 70, 40} }, // { 1, 7, 9 }
+ { {100, 50}, { 70, 40}, {110, 20} }, // { 1, 9, 0 }
+ { { 90, 80}, { 70, 120}, { 50, 80} }, // { 3, 4, 5 }
+ { {130, 80}, { 90, 80}, { 50, 80} }, // { 2, 3, 5 } degen
+ { {130, 80}, { 50, 80}, { 10, 80} }, // { 2, 5, 6 } degen
+ { {130, 80}, { 10, 80}, {100, 50} } // { 2, 6, 1 }
+ };
+ const size_t numRefTriangles = sizeof(refTriangles)
+ / (6 * sizeof(refTriangles[0][0][0]));
+ SkTDArray<SkPoint> triangles;
+ bool success = SkConcaveToTriangles(kNumStarVertices, star, &triangles);
+ PrintTriangles(triangles, kNumStarVertices, star, reporter);
+ success = CompareTriangleList(numRefTriangles, refTriangles, triangles)
+ && success;
+ reporter->report("Triangulate Star", success ? reporter->kPassed
+ : reporter->kFailed);
+}
+
+
+// Star with hole test
+static void TestStarHoleTriangulation(skiatest::Reporter* reporter) {
+ static const float refTriangles[][3][2] = {
+ { {100, 50}, { 80, 60}, { 70, 50} }, // { 1, 15, 16 }
+ { {100, 50}, { 70, 50}, {110, 20} }, // { 1, 16, 0 }
+ { { 30, 20}, { 70, 40}, { 40, 50} }, // { 8, 9, 7 }
+ { { 60, 70}, { 80, 70}, { 10, 80} }, // { 13, 14, 6 }
+ { { 60, 60}, { 60, 70}, { 10, 80} }, // { 12, 13, 6 }
+ { { 70, 50}, { 60, 60}, { 10, 80} }, // { 11, 12, 6 }
+ { { 70, 50}, { 10, 80}, { 40, 50} }, // { 11, 6, 7 }
+ { { 70, 50}, { 40, 50}, { 70, 40} }, // { 11, 7, 9 }
+ { { 70, 50}, { 70, 40}, {110, 20} }, // { 11, 9, 10 }
+ { { 90, 80}, { 70, 120}, { 50, 80} }, // { 3, 4, 5 }
+ { {130, 80}, { 90, 80}, { 50, 80} }, // { 2, 3, 5 } degen
+ { {130, 80}, { 50, 80}, { 10, 80} }, // { 2, 5, 6 } degen
+ { {130, 80}, { 10, 80}, { 80, 70} }, // { 2, 6, 14 }
+ { {130, 80}, { 80, 70}, { 80, 60} }, // { 2, 14, 15 }
+ { {130, 80}, { 80, 60}, {100, 50} } // { 2, 15, 1 }
+ };
+ const size_t numRefTriangles = sizeof(refTriangles)
+ / (6 * sizeof(refTriangles[0][0][0]));
+ SkTDArray<SkPoint> triangles;
+ bool success = SkConcaveToTriangles(kNumStarHoleVertices, star, &triangles);
+ PrintTriangles(triangles, kNumStarHoleVertices, star, reporter);
+ success = CompareTriangleList(numRefTriangles, refTriangles, triangles)
+ && success;
+ reporter->report("Triangulate Star With Hole", success ? reporter->kPassed
+ : reporter->kFailed);
+}
+
+
+// Plus test
+static void TestPlusTriangulation(skiatest::Reporter* reporter) {
+ static const float refTriangles[][3][2] = {
+ { { 50, 10}, { 70, 10}, { 50, 50} }, // { 11, 0, 10 }
+ { { 70, 50}, {110, 50}, { 10, 70} }, // { 1, 2, 8 }
+ { { 70, 50}, { 10, 70}, { 10, 50} }, // { 1, 8, 9 }
+ { { 70, 50}, { 10, 50}, { 50, 50} }, // { 1, 9, 10 }
+ { { 70, 50}, { 50, 50}, { 70, 10} }, // { 1, 10, 0 }
+ { { 70, 70}, { 50, 110}, { 50, 70} }, // { 4, 6, 7 }
+ { {110, 70}, { 70, 70}, { 50, 70} }, // { 3, 4, 7 }
+ { {110, 70}, { 50, 70}, { 10, 70} }, // { 3, 7, 8 }
+ { {110, 70}, { 10, 70}, {110, 50} }, // { 3, 8, 2 }
+ { { 70, 110}, { 50, 110}, { 70, 70} }, // { 5, 6, 4 }
+ };
+ const size_t numRefTriangles = sizeof(refTriangles)
+ / (6 * sizeof(refTriangles[0][0][0]));
+ SkTDArray<SkPoint> triangles;
+ const size_t numVertices = sizeof(plus) / sizeof(SkPoint);
+ bool success = SkConcaveToTriangles(numVertices, plus, &triangles);
+ PrintTriangles(triangles, numVertices, plus, reporter);
+ success = CompareTriangleList(numRefTriangles, refTriangles, triangles)
+ && success;
+ reporter->report("Triangulate Plus", success ? reporter->kPassed
+ : reporter->kFailed);
+}
+
+
+// Zipper test
+static void TestZipperTriangulation(skiatest::Reporter* reporter) {
+ static const float refTriangles[][3][2] = {
+ { { 10, 10}, { 20, 10}, { 20, 50} }, // { 1, 2, 3 }
+ { { 20, 50}, { 30, 50}, { 10, 60} }, // { 3, 4, 0 }
+ { { 10, 10}, { 20, 50}, { 10, 60} }, // { 1, 3, 0 }
+ { { 30, 10}, { 60, 10}, { 40, 20} }, // { 5, 6, 26 }
+ { { 30, 10}, { 40, 20}, { 30, 50} }, // { 5, 26, 4 }
+ { { 40, 60}, { 10, 60}, { 30, 50} }, // { 27, 0, 4 }
+ { { 40, 60}, { 30, 50}, { 40, 20} }, // { 27, 4, 26 }
+ { { 60, 50}, { 70, 50}, { 50, 60} }, // { 7, 8, 24 }
+ { { 50, 20}, { 60, 50}, { 50, 60} }, // { 25, 7, 24 }
+ { { 50, 20}, { 40, 20}, { 60, 10} }, // { 25, 26, 6 }
+ { { 60, 50}, { 50, 20}, { 60, 10} }, // { 7, 25, 6 }
+ { { 70, 10}, {100, 10}, { 80, 20} }, // { 9, 10, 22 }
+ { { 70, 10}, { 80, 20}, { 70, 50} }, // { 9, 22, 8 }
+ { { 80, 60}, { 50, 60}, { 70, 50} }, // { 23, 24, 8 }
+ { { 80, 60}, { 70, 50}, { 80, 20} }, // { 23, 8, 22 }
+ { {100, 50}, {110, 50}, { 90, 60} }, // { 11, 12, 20 }
+ { { 90, 20}, {100, 50}, { 90, 60} }, // { 21, 11, 20 }
+ { { 90, 20}, { 80, 20}, {100, 10} }, // { 21, 22, 10 }
+ { {100, 50}, { 90, 20}, {100, 10} }, // { 11, 21, 10 }
+ { {110, 10}, {140, 10}, {120, 20} }, // { 13, 14, 18 }
+ { {110, 10}, {120, 20}, {110, 50} }, // { 13, 18, 12 }
+ { {120, 60}, { 90, 60}, {110, 50} }, // { 19, 20, 12 }
+ { {120, 60}, {110, 50}, {120, 20} }, // { 19, 12, 18 }
+ { {140, 60}, {130, 60}, {130, 20} }, // { 15, 16, 17 }
+ { {130, 20}, {120, 20}, {140, 10} }, // { 17, 18, 14 }
+ { {140, 60}, {130, 20}, {140, 10} }, // { 15, 17, 14 }
+ };
+ const size_t numRefTriangles = sizeof(refTriangles)
+ / (6 * sizeof(refTriangles[0][0][0]));
+ SkTDArray<SkPoint> triangles;
+ const size_t numVertices = sizeof(zipper) / sizeof(SkPoint);
+ bool success = SkConcaveToTriangles(numVertices, zipper, &triangles);
+ PrintTriangles(triangles, numVertices, zipper, reporter);
+ success = CompareTriangleList(numRefTriangles, refTriangles, triangles)
+ && success;
+ reporter->report("Triangulate Zipper", success ? reporter->kPassed
+ : reporter->kFailed);
+}
+
+
+static void TestTriangulation(skiatest::Reporter* reporter) {
+ TestStarTriangulation(reporter);
+ TestStarHoleTriangulation(reporter);
+ TestPlusTriangulation(reporter);
+ TestZipperTriangulation(reporter);
+}
+
+#include "TestClassDef.h"
+DEFINE_TESTCLASS("Triangulation", TriangulationTestClass, TestTriangulation)