aboutsummaryrefslogtreecommitdiffhomepage
diff options
context:
space:
mode:
Diffstat
-rw-r--r--include/utils/SkMatrix44.h18
-rw-r--r--src/utils/SkMatrix44.cpp40
-rw-r--r--tests/Matrix44Test.cpp213
3 files changed, 271 insertions, 0 deletions
diff --git a/include/utils/SkMatrix44.h b/include/utils/SkMatrix44.h
index 83b5443d68..38a011467f 100644
--- a/include/utils/SkMatrix44.h
+++ b/include/utils/SkMatrix44.h
@@ -29,6 +29,9 @@
static inline double SkMScalarToDouble(double x) {
return x;
}
+ static inline double SkMScalarAbs(double x) {
+ return fabs(x);
+ }
static const SkMScalar SK_MScalarPI = 3.141592653589793;
#elif defined SK_MSCALAR_IS_FLOAT
#ifdef SK_MSCALAR_IS_DOUBLE
@@ -48,6 +51,9 @@
static inline double SkMScalarToDouble(float x) {
return static_cast<double>(x);
}
+ static inline float SkMScalarAbs(float x) {
+ return sk_float_abs(x);
+ }
static const SkMScalar SK_MScalarPI = 3.14159265f;
#endif
@@ -377,6 +383,18 @@ public:
void map2(const float src2[], int count, float dst4[]) const;
void map2(const double src2[], int count, double dst4[]) const;
+ /** Returns true if transformating an axis-aligned square in 2d by this matrix
+ will produce another 2d axis-aligned square; typically means the matrix
+ is a scale with perhaps a 90-degree rotation. A 3d rotation through 90
+ degrees into a perpendicular plane collapses a square to a line, but
+ is still considered to be axis-aligned.
+
+ By default, tolerates very slight error due to float imprecisions;
+ a 90-degree rotation can still end up with 10^-17 of
+ "non-axis-aligned" result.
+ */
+ bool preserves2dAxisAlignment(SkMScalar epsilon = SK_ScalarNearlyZero) const;
+
void dump() const;
double determinant() const;
diff --git a/src/utils/SkMatrix44.cpp b/src/utils/SkMatrix44.cpp
index a7133ec1a7..1835635f1d 100644
--- a/src/utils/SkMatrix44.cpp
+++ b/src/utils/SkMatrix44.cpp
@@ -857,6 +857,46 @@ void SkMatrix44::map2(const double src2[], int count, double dst4[]) const {
proc(fMat, src2, count, dst4);
}
+bool SkMatrix44::preserves2dAxisAlignment (SkMScalar epsilon) const {
+
+ // Can't check (mask & kPerspective_Mask) because Z isn't relevant here.
+ if (0 != perspX() || 0 != perspY()) return false;
+
+ // A matrix with two non-zeroish values in any of the upper right
+ // rows or columns will skew. If only one value in each row or
+ // column is non-zeroish, we get a scale plus perhaps a 90-degree
+ // rotation.
+ int col0 = 0;
+ int col1 = 0;
+ int row0 = 0;
+ int row1 = 0;
+
+ // Must test against epsilon, not 0, because we can get values
+ // around 6e-17 in the matrix that "should" be 0.
+
+ if (SkMScalarAbs(fMat[0][0]) > epsilon) {
+ col0++;
+ row0++;
+ }
+ if (SkMScalarAbs(fMat[0][1]) > epsilon) {
+ col1++;
+ row0++;
+ }
+ if (SkMScalarAbs(fMat[1][0]) > epsilon) {
+ col0++;
+ row1++;
+ }
+ if (SkMScalarAbs(fMat[1][1]) > epsilon) {
+ col1++;
+ row1++;
+ }
+ if (col0 > 1 || col1 > 1 || row0 > 1 || row1 > 1) {
+ return false;
+ }
+
+ return true;
+}
+
///////////////////////////////////////////////////////////////////////////////
void SkMatrix44::dump() const {
diff --git a/tests/Matrix44Test.cpp b/tests/Matrix44Test.cpp
index 0bd4a8ba13..75dd5181d4 100644
--- a/tests/Matrix44Test.cpp
+++ b/tests/Matrix44Test.cpp
@@ -550,6 +550,218 @@ static void test_has_perspective(skiatest::Reporter* reporter) {
REPORTER_ASSERT(reporter, transform.hasPerspective());
}
+static bool is_rectilinear (SkVector4& p1, SkVector4& p2, SkVector4& p3, SkVector4& p4) {
+ return (SkScalarNearlyEqual(p1.fData[0], p2.fData[0]) &&
+ SkScalarNearlyEqual(p2.fData[1], p3.fData[1]) &&
+ SkScalarNearlyEqual(p3.fData[0], p4.fData[0]) &&
+ SkScalarNearlyEqual(p4.fData[1], p1.fData[1])) ||
+ (SkScalarNearlyEqual(p1.fData[1], p2.fData[1]) &&
+ SkScalarNearlyEqual(p2.fData[0], p3.fData[0]) &&
+ SkScalarNearlyEqual(p3.fData[1], p4.fData[1]) &&
+ SkScalarNearlyEqual(p4.fData[0], p1.fData[0]));
+}
+
+static SkVector4 mul_with_persp_divide(const SkMatrix44& transform, const SkVector4& target) {
+ SkVector4 result = transform * target;
+ if (result.fData[3] != 0.0f && result.fData[3] != SK_Scalar1) {
+ float wInverse = SK_Scalar1 / result.fData[3];
+ result.set(result.fData[0] * wInverse,
+ result.fData[1] * wInverse,
+ result.fData[2] * wInverse,
+ SK_Scalar1);
+ }
+ return result;
+}
+
+static bool empirically_preserves_2d_axis_alignment(skiatest::Reporter* reporter,
+ const SkMatrix44& transform) {
+ SkVector4 p1(5.0f, 5.0f, 0.0f);
+ SkVector4 p2(10.0f, 5.0f, 0.0f);
+ SkVector4 p3(10.0f, 20.0f, 0.0f);
+ SkVector4 p4(5.0f, 20.0f, 0.0f);
+
+ REPORTER_ASSERT(reporter, is_rectilinear(p1, p2, p3, p4));
+
+ p1 = mul_with_persp_divide(transform, p1);
+ p2 = mul_with_persp_divide(transform, p2);
+ p3 = mul_with_persp_divide(transform, p3);
+ p4 = mul_with_persp_divide(transform, p4);
+
+ return is_rectilinear(p1, p2, p3, p4);
+}
+
+static void test(bool expected, skiatest::Reporter* reporter, const SkMatrix44& transform) {
+ if (expected) {
+ REPORTER_ASSERT(reporter, empirically_preserves_2d_axis_alignment(reporter, transform));
+ REPORTER_ASSERT(reporter, transform.preserves2dAxisAlignment());
+ } else {
+ REPORTER_ASSERT(reporter, !empirically_preserves_2d_axis_alignment(reporter, transform));
+ REPORTER_ASSERT(reporter, !transform.preserves2dAxisAlignment());
+ }
+}
+
+static void test_preserves_2d_axis_alignment(skiatest::Reporter* reporter) {
+ SkMatrix44 transform(SkMatrix44::kUninitialized_Constructor);
+ SkMatrix44 transform2(SkMatrix44::kUninitialized_Constructor);
+
+ static const struct TestCase {
+ SkMScalar a; // row 1, column 1
+ SkMScalar b; // row 1, column 2
+ SkMScalar c; // row 2, column 1
+ SkMScalar d; // row 2, column 2
+ bool expected;
+ } test_cases[] = {
+ { 3.f, 0.f,
+ 0.f, 4.f, true }, // basic case
+ { 0.f, 4.f,
+ 3.f, 0.f, true }, // rotate by 90
+ { 0.f, 0.f,
+ 0.f, 4.f, true }, // degenerate x
+ { 3.f, 0.f,
+ 0.f, 0.f, true }, // degenerate y
+ { 0.f, 0.f,
+ 3.f, 0.f, true }, // degenerate x + rotate by 90
+ { 0.f, 4.f,
+ 0.f, 0.f, true }, // degenerate y + rotate by 90
+ { 3.f, 4.f,
+ 0.f, 0.f, false },
+ { 0.f, 0.f,
+ 3.f, 4.f, false },
+ { 0.f, 3.f,
+ 0.f, 4.f, false },
+ { 3.f, 0.f,
+ 4.f, 0.f, false },
+ { 3.f, 4.f,
+ 5.f, 0.f, false },
+ { 3.f, 4.f,
+ 0.f, 5.f, false },
+ { 3.f, 0.f,
+ 4.f, 5.f, false },
+ { 0.f, 3.f,
+ 4.f, 5.f, false },
+ { 2.f, 3.f,
+ 4.f, 5.f, false },
+ };
+
+ for (size_t i = 0; i < sizeof(test_cases)/sizeof(TestCase); ++i) {
+ const TestCase& value = test_cases[i];
+ transform.setIdentity();
+ transform.set(0, 0, value.a);
+ transform.set(0, 1, value.b);
+ transform.set(1, 0, value.c);
+ transform.set(1, 1, value.d);
+
+ test(value.expected, reporter, transform);
+ }
+
+ // Try the same test cases again, but this time make sure that other matrix
+ // elements (except perspective) have entries, to test that they are ignored.
+ for (size_t i = 0; i < sizeof(test_cases)/sizeof(TestCase); ++i) {
+ const TestCase& value = test_cases[i];
+ transform.setIdentity();
+ transform.set(0, 0, value.a);
+ transform.set(0, 1, value.b);
+ transform.set(1, 0, value.c);
+ transform.set(1, 1, value.d);
+
+ transform.set(0, 2, 1.f);
+ transform.set(0, 3, 2.f);
+ transform.set(1, 2, 3.f);
+ transform.set(1, 3, 4.f);
+ transform.set(2, 0, 5.f);
+ transform.set(2, 1, 6.f);
+ transform.set(2, 2, 7.f);
+ transform.set(2, 3, 8.f);
+
+ test(value.expected, reporter, transform);
+ }
+
+ // Try the same test cases again, but this time add perspective which is
+ // always assumed to not-preserve axis alignment.
+ for (size_t i = 0; i < sizeof(test_cases)/sizeof(TestCase); ++i) {
+ const TestCase& value = test_cases[i];
+ transform.setIdentity();
+ transform.set(0, 0, value.a);
+ transform.set(0, 1, value.b);
+ transform.set(1, 0, value.c);
+ transform.set(1, 1, value.d);
+
+ transform.set(0, 2, 1.f);
+ transform.set(0, 3, 2.f);
+ transform.set(1, 2, 3.f);
+ transform.set(1, 3, 4.f);
+ transform.set(2, 0, 5.f);
+ transform.set(2, 1, 6.f);
+ transform.set(2, 2, 7.f);
+ transform.set(2, 3, 8.f);
+ transform.set(3, 0, 9.f);
+ transform.set(3, 1, 10.f);
+ transform.set(3, 2, 11.f);
+ transform.set(3, 3, 12.f);
+
+ test(false, reporter, transform);
+ }
+
+ // Try a few more practical situations to check precision
+ // Reuse TestCase (a, b, c, d) as (x, y, z, degrees) axis to rotate about.
+ TestCase rotation_tests[] = {
+ { 0.0, 0.0, 1.0, 90.0, true },
+ { 0.0, 0.0, 1.0, 180.0, true },
+ { 0.0, 0.0, 1.0, 270.0, true },
+ { 0.0, 1.0, 0.0, 90.0, true },
+ { 1.0, 0.0, 0.0, 90.0, true },
+ { 0.0, 0.0, 1.0, 45.0, false },
+ // In 3d these next two are non-preserving, but we're testing in 2d after
+ // orthographic projection, where they are.
+ { 0.0, 1.0, 0.0, 45.0, true },
+ { 1.0, 0.0, 0.0, 45.0, true },
+ };
+
+ for (size_t i = 0; i < sizeof(rotation_tests)/sizeof(TestCase); ++i) {
+ const TestCase& value = rotation_tests[i];
+ transform.setRotateDegreesAbout(value.a, value.b, value.c, value.d);
+ test(value.expected, reporter, transform);
+ }
+
+ static const struct DoubleRotationCase {
+ SkMScalar x1;
+ SkMScalar y1;
+ SkMScalar z1;
+ SkMScalar degrees1;
+ SkMScalar x2;
+ SkMScalar y2;
+ SkMScalar z2;
+ SkMScalar degrees2;
+ bool expected;
+ } double_rotation_tests[] = {
+ { 0.0, 0.0, 1.0, 90.0, 0.0, 1.0, 0.0, 90.0, true },
+ { 0.0, 0.0, 1.0, 90.0, 1.0, 0.0, 0.0, 90.0, true },
+ { 0.0, 1.0, 0.0, 90.0, 0.0, 0.0, 1.0, 90.0, true },
+ };
+
+ for (size_t i = 0; i < sizeof(double_rotation_tests)/sizeof(DoubleRotationCase); ++i) {
+ const DoubleRotationCase& value = double_rotation_tests[i];
+ transform.setRotateDegreesAbout(value.x1, value.y1, value.z1, value.degrees1);
+ transform2.setRotateDegreesAbout(value.x2, value.y2, value.z2, value.degrees2);
+ transform.postConcat(transform2);
+ test(value.expected, reporter, transform);
+ }
+
+ // Perspective cases.
+ transform.setIdentity();
+ transform.set(3, 2, -0.1); // Perspective depth 10
+ transform2.setRotateDegreesAbout(0.0, 1.0, 0.0, 45.0);
+ transform.preConcat(transform2);
+ test(false, reporter, transform);
+
+ transform.setIdentity();
+ transform.set(3, 2, -0.1); // Perspective depth 10
+ transform2.setRotateDegreesAbout(0.0, 0.0, 1.0, 90.0);
+ transform.preConcat(transform2);
+ test(true, reporter, transform);
+}
+
+
DEF_TEST(Matrix44, reporter) {
SkMatrix44 mat(SkMatrix44::kUninitialized_Constructor);
SkMatrix44 inverse(SkMatrix44::kUninitialized_Constructor);
@@ -656,4 +868,5 @@ DEF_TEST(Matrix44, reporter) {
test_map2(reporter);
test_3x3_conversion(reporter);
test_has_perspective(reporter);
+ test_preserves_2d_axis_alignment(reporter);
}
generated by cgit v1.2.3 (git 2.39.1) at 2024-06-07 12:28:17 +0000