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Ink Open Source
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Add a short circuit for EvaluateTangentQuality to improve performance
To do that, the function had to move from brush_tip_shape.h to brush_tip_extrusion.h PiperOrigin-RevId: 676868506
1 parent 2173e70 commit 7cfc270

9 files changed

+382
-298
lines changed

‎ink/strokes/internal/BUILD.bazel

+18-3
Original file line numberDiff line numberDiff line change
@@ -260,7 +260,6 @@ cc_library(
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":brush_tip_state",
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":circular_extrusion_helpers",
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":extrusion_points",
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":rounded_polygon",
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"//ink/geometry:affine_transform",
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"//ink/geometry:angle",
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"//ink/geometry:point",
@@ -295,10 +294,28 @@ cc_test(
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cc_library(
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name = "brush_tip_extrusion",
297+
srcs = ["brush_tip_extrusion.cc"],
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hdrs = ["brush_tip_extrusion.h"],
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deps = [
300300
":brush_tip_shape",
301301
":brush_tip_state",
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":rounded_polygon",
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"//ink/geometry:distance",
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"//ink/geometry:rect",
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"//ink/geometry/internal:circle",
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"@com_google_absl//absl/container:inlined_vector",
307+
"@com_google_absl//absl/log:absl_check",
308+
"@com_google_absl//absl/types:span",
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],
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)
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cc_test(
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name = "brush_tip_extrusion_test",
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srcs = ["brush_tip_extrusion_test.cc"],
315+
deps = [
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":brush_tip_extrusion",
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"//ink/geometry:angle",
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"@com_google_googletest//:gtest_main",
302319
],
303320
)
304321

@@ -514,7 +531,6 @@ cc_library(
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hdrs = ["constrain_brush_tip_extrusion.h"],
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deps = [
516533
":brush_tip_extrusion",
517-
":brush_tip_shape",
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":brush_tip_state",
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"//ink/geometry:distance",
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"//ink/geometry/internal:algorithms",
@@ -527,7 +543,6 @@ cc_test(
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srcs = ["constrain_brush_tip_extrusion_test.cc"],
528544
deps = [
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":brush_tip_extrusion",
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":brush_tip_shape",
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":brush_tip_state",
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":constrain_brush_tip_extrusion",
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":type_matchers",

‎ink/strokes/internal/brush_tip_extrusion.cc

+161
Original file line numberDiff line numberDiff line change
@@ -0,0 +1,161 @@
1+
#include "ink/strokes/internal/brush_tip_extrusion.h"
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#include <algorithm>
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#include <cstdlib>
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#include "absl/container/inlined_vector.h"
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#include "absl/log/absl_check.h"
8+
#include "absl/types/span.h"
9+
#include "ink/geometry/distance.h"
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#include "ink/geometry/internal/circle.h"
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#include "ink/geometry/rect.h"
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#include "ink/strokes/internal/brush_tip_shape.h"
13+
#include "ink/strokes/internal/brush_tip_state.h"
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#include "ink/strokes/internal/rounded_polygon.h"
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namespace ink::strokes_internal {
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namespace {
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using ::ink::geometry_internal::Circle;
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// Constructs a `RoundedPolygon` representing the shape that results from
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// connecting `first` and `second` by the tangents of the circles indicated by
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// `indices`. The returned shape starts at `indices.left.first`, proceeds to
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// `indices.right.first`, then jumps to `indices.right.second` and proceeds to
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// `indices.left.second`, always moving counter-clockwise per
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// `GetNextPerimeterIndexCcw`. `indices` is expected to be the result of calling
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// `GetTangentCircleIndices(first, second)`. `first` must not contain `second`,
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// and vice versa.
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//
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// `offset` specifies how much the returned `RoundedPolygon` should be offset
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// from the actual joined shape. This value must be >= 0.
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//
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// Note that not all of the component circles of `first` and `second` are
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// guaranteed to be contained in the returned shape; e.g. you could have two
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// rectangular `BrushTipShape`s that form a cross, which would leave two
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// circles outside the `RoundedPolygon`.
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static RoundedPolygon ConstructJoinedShape(
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const BrushTipShape& first, const BrushTipShape& second,
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const BrushTipShape::TangentCircleIndices& indices, float offset) {
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ABSL_DCHECK(!first.Contains(second));
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ABSL_DCHECK(!second.Contains(first));
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ABSL_CHECK_GE(offset, 0);
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// Each `BrushTipShape` has at most four circles, so we need at most eight
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// for the `RoundedPolygon`.
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absl::InlinedVector<Circle, 8> circles;
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auto add_circles = [&circles, offset](const BrushTipShape& shape,
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int first_index, int last_index) {
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auto add_one_circle_with_offset = [&circles, offset](const Circle& circle) {
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circles.push_back({circle.Center(), circle.Radius() + offset});
52+
};
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if (first_index == last_index) {
54+
add_one_circle_with_offset(shape.PerimeterCircles()[first_index]);
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} else {
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for (int index = first_index; index != last_index;
57+
index = shape.GetNextPerimeterIndexCcw(index)) {
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add_one_circle_with_offset(shape.PerimeterCircles()[index]);
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}
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add_one_circle_with_offset(shape.PerimeterCircles()[last_index]);
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}
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};
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add_circles(first, indices.left.first, indices.right.first);
65+
add_circles(second, indices.right.second, indices.left.second);
66+
67+
return RoundedPolygon(circles);
68+
}
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BrushTipExtrusion::TangentQuality EvaluateTangentQualityInternal(
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const BrushTipShape& first, const BrushTipShape& second) {
72+
if (first.Contains(second)) {
73+
return BrushTipExtrusion::TangentQuality::kNoTangentsFirstContainsSecond;
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}
75+
76+
if ((second.Contains(first))) {
77+
return BrushTipExtrusion::TangentQuality::kNoTangentsSecondContainsFirst;
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}
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// If we have two circles that don't contain each other, then we can always
81+
// construct good tangents.
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// NOMUTANTS -- this is just a short-circuit for performance.
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if (first.PerimeterCircles().size() == 1 &&
84+
second.PerimeterCircles().size() == 1) {
85+
return BrushTipExtrusion::TangentQuality::kGoodTangents;
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}
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88+
// Fetch the indices of the circles that will be connect the two shapes.
89+
BrushTipShape::TangentCircleIndices indices =
90+
BrushTipShape::GetTangentCircleIndices(first, second);
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// If the first circle is immediately *clockwise* to the last circle for
93+
// each shape, then all circles contribute to the boundary of the joined
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// shape and there are no unused circles.
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// NOMUTANTS -- This is just a short-circuit for performance.
96+
if (first.GetNextPerimeterIndexCw(indices.left.first) ==
97+
indices.right.first &&
98+
second.GetNextPerimeterIndexCw(indices.right.second) ==
99+
indices.left.second) {
100+
return BrushTipExtrusion::TangentQuality::kGoodTangents;
101+
}
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103+
// In order to avoid false-negatives from `RoundedPolygon::ContainsCircle` due
104+
// to floating-point precision issues, we enlarge the joined shape by a small
105+
// amount.
106+
Rect first_bounds = first.Bounds();
107+
Rect second_bounds = second.Bounds();
108+
float max_absolute_coordinate = std::max(
109+
{std::abs(first_bounds.XMin()), std::abs(first_bounds.XMax()),
110+
std::abs(first_bounds.YMin()), std::abs(first_bounds.YMax()),
111+
std::abs(second_bounds.XMin()), std::abs(second_bounds.XMax()),
112+
std::abs(second_bounds.YMin()), std::abs(second_bounds.YMax())});
113+
float offset = 1e-6 * max_absolute_coordinate;
114+
115+
// Construct the joined shape, with the offset.
116+
RoundedPolygon joined_shape =
117+
ConstructJoinedShape(first, second, indices, offset);
118+
119+
// Finally, check whether the unused circles are contained inside the joined
120+
// shape.
121+
for (int index = first.GetNextPerimeterIndexCcw(indices.right.first);
122+
index != indices.left.first;
123+
index = first.GetNextPerimeterIndexCcw(index)) {
124+
if (!joined_shape.ContainsCircle(first.PerimeterCircles()[index]))
125+
return BrushTipExtrusion::TangentQuality::
126+
kBadTangentsJoinedShapeDoesNotCoverInputShapes;
127+
}
128+
for (int index = second.GetNextPerimeterIndexCcw(indices.left.second);
129+
index != indices.right.second;
130+
index = second.GetNextPerimeterIndexCcw(index)) {
131+
if (!joined_shape.ContainsCircle(second.PerimeterCircles()[index]))
132+
return BrushTipExtrusion::TangentQuality::
133+
kBadTangentsJoinedShapeDoesNotCoverInputShapes;
134+
}
135+
136+
return BrushTipExtrusion::TangentQuality::kGoodTangents;
137+
}
138+
139+
bool StatesHaveEqualShapeProperties(const BrushTipState& first,
140+
const BrushTipState& second) {
141+
return first.width == second.width && first.height == second.height &&
142+
first.percent_radius == second.percent_radius &&
143+
first.rotation == second.rotation && first.slant == second.slant &&
144+
first.pinch == second.pinch;
145+
}
146+
147+
} // namespace
148+
149+
BrushTipExtrusion::TangentQuality BrushTipExtrusion::EvaluateTangentQuality(
150+
const BrushTipExtrusion& first, const BrushTipExtrusion& second,
151+
float travel_threshold) {
152+
if ((Distance(first.GetState().position, second.GetState().position)) >
153+
travel_threshold &&
154+
StatesHaveEqualShapeProperties(first.GetState(), second.GetState())) {
155+
return TangentQuality::kGoodTangents;
156+
}
157+
158+
return EvaluateTangentQualityInternal(first.GetShape(), second.GetShape());
159+
}
160+
161+
} // namespace ink::strokes_internal

‎ink/strokes/internal/brush_tip_extrusion.h

+21
Original file line numberDiff line numberDiff line change
@@ -45,6 +45,27 @@ class BrushTipExtrusion {
4545
const BrushTipState& GetState() const { return tip_state_and_shape_->first; }
4646
const BrushTipShape& GetShape() const { return tip_state_and_shape_->second; }
4747

48+
// Evaluates whether we can construct tangents between `first` and `second`,
49+
// and whether those tangents are "good"; i.e. whether the shape formed by
50+
// connecting `first` and `second` covers all of `first` and `second`.
51+
enum class TangentQuality {
52+
// We can't construct tangents, because `first` contains `second`.
53+
kNoTangentsFirstContainsSecond,
54+
// We can't construct tangents, because `second` contains `first`.
55+
kNoTangentsSecondContainsFirst,
56+
// We can construct tangents, but the joined shape doesn't cover all of
57+
// `first` and `second`.
58+
kBadTangentsJoinedShapeDoesNotCoverInputShapes,
59+
// We can construct tangents, and the joined shape covers `first` and
60+
// `second`.
61+
kGoodTangents,
62+
};
63+
// `travel_threshold` is used to determine if the centers of the extrusions
64+
// are sufficiently close to be considered not moving.
65+
static TangentQuality EvaluateTangentQuality(const BrushTipExtrusion& first,
66+
const BrushTipExtrusion& second,
67+
float travel_threshold);
68+
4869
private:
4970
std::optional<std::pair<BrushTipState, BrushTipShape>> tip_state_and_shape_;
5071
};

‎ink/strokes/internal/brush_tip_extrusion_test.cc

+151
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@@ -0,0 +1,151 @@
1+
#include "ink/strokes/internal/brush_tip_extrusion.h"
2+
3+
#include "gtest/gtest.h"
4+
#include "ink/geometry/angle.h"
5+
6+
namespace ink::strokes_internal {
7+
namespace {
8+
9+
constexpr float kEpsilon = 1e-5;
10+
constexpr float kTravelThreshold = kEpsilon * 0.1;
11+
12+
TEST(BrushTipExtrusionTest, EvaluateTangentQualityTwoNonOverlappingCircles) {
13+
EXPECT_EQ(
14+
BrushTipExtrusion::EvaluateTangentQuality(
15+
{{.position = {0, 0}, .width = 1, .height = 1, .percent_radius = 1},
16+
kEpsilon},
17+
{{.position = {2, 1}, .width = 1, .height = 1, .percent_radius = 1},
18+
kEpsilon},
19+
kTravelThreshold),
20+
BrushTipExtrusion::TangentQuality::kGoodTangents);
21+
}
22+
23+
TEST(BrushTipExtrusionTest, EvaluateTangentQualityTwoNonOverlappingSquares) {
24+
EXPECT_EQ(BrushTipExtrusion::EvaluateTangentQuality(
25+
{{.position = {0, 0}, .width = 1, .height = 1}, kEpsilon},
26+
{{.position = {2, 1}, .width = 1, .height = 1}, kEpsilon},
27+
kTravelThreshold),
28+
BrushTipExtrusion::TangentQuality::kGoodTangents);
29+
}
30+
31+
TEST(BrushTipExtrusionTest, EvaluateTangentQualityTwoNonOverlappingStadiums) {
32+
EXPECT_EQ(
33+
BrushTipExtrusion::EvaluateTangentQuality(
34+
{{.position = {0, 0}, .width = 1, .height = 1, .percent_radius = 0.5},
35+
kEpsilon},
36+
{{.position = {2, 1}, .width = 1, .height = 1, .percent_radius = 0.5},
37+
kEpsilon},
38+
kTravelThreshold),
39+
BrushTipExtrusion::TangentQuality::kGoodTangents);
40+
}
41+
42+
TEST(BrushTipExtrusionTest,
43+
EvaluateTangentQualityTwoTrapezoidsPointingInOppositeDirections) {
44+
EXPECT_EQ(BrushTipExtrusion::EvaluateTangentQuality({{.position = {-1, 0},
45+
.width = 1,
46+
.height = 1,
47+
.rotation = -kHalfPi,
48+
.pinch = 0.5},
49+
kTravelThreshold},
50+
{{.position = {1, 0},
51+
.width = 1,
52+
.height = 1,
53+
.rotation = kHalfPi,
54+
.pinch = 0.5},
55+
kEpsilon},
56+
kTravelThreshold),
57+
BrushTipExtrusion::TangentQuality::kGoodTangents);
58+
}
59+
60+
TEST(BrushTipExtrusionTest,
61+
EvaluateTangentQualityTwoRoundedTrapezoidsPointingInOppositeDirections) {
62+
EXPECT_EQ(BrushTipExtrusion::EvaluateTangentQuality({{.position = {-1, 0},
63+
.width = 1,
64+
.height = 1,
65+
.percent_radius = 0.5,
66+
.rotation = -kHalfPi,
67+
.pinch = 0.5},
68+
kTravelThreshold},
69+
{{.position = {1, 0},
70+
.width = 1,
71+
.height = 1,
72+
.percent_radius = 0.5,
73+
.rotation = kHalfPi,
74+
.pinch = 0.5},
75+
kEpsilon},
76+
kTravelThreshold),
77+
BrushTipExtrusion::TangentQuality::kGoodTangents);
78+
}
79+
80+
TEST(BrushTipExtrusionTest, JoinedShapeTwoPillsAtRightAngles) {
81+
EXPECT_EQ(
82+
BrushTipExtrusion::EvaluateTangentQuality(
83+
{{.position = {0, 0}, .width = 2, .height = 1, .percent_radius = 1},
84+
kEpsilon},
85+
{{.position = {2, 0},
86+
.width = 2,
87+
.height = 1,
88+
.percent_radius = 1,
89+
.rotation = kHalfPi},
90+
kEpsilon},
91+
kTravelThreshold),
92+
BrushTipExtrusion::TangentQuality::kGoodTangents);
93+
}
94+
95+
TEST(BrushTipExtrusionTest,
96+
EvaluateTangentQualityCrossedRectanglesFirstShapeNotFullyCovered) {
97+
EXPECT_EQ(BrushTipExtrusion::EvaluateTangentQuality(
98+
{{.position = {0, 0}, .width = 3, .height = 1}, kEpsilon},
99+
{{.position = {0.5, 0}, .width = 1, .height = 2}, kEpsilon},
100+
kTravelThreshold),
101+
BrushTipExtrusion::TangentQuality::
102+
kBadTangentsJoinedShapeDoesNotCoverInputShapes);
103+
}
104+
105+
TEST(BrushTipExtrusionTest,
106+
EvaluateTangentQualityCrossedRectanglesSecondShapeNotFullyCovered) {
107+
EXPECT_EQ(BrushTipExtrusion::EvaluateTangentQuality(
108+
{{.position = {0, 0}, .width = 1, .height = 2}, kEpsilon},
109+
{{.position = {0.5, 0}, .width = 3, .height = 1}, kEpsilon},
110+
kTravelThreshold),
111+
BrushTipExtrusion::TangentQuality::
112+
kBadTangentsJoinedShapeDoesNotCoverInputShapes);
113+
}
114+
115+
TEST(BrushTipExtrusionTest, EvaluateTangentQualityFirstShapeContainsSecond) {
116+
EXPECT_EQ(BrushTipExtrusion::EvaluateTangentQuality(
117+
{{.position = {0, 0}, .width = 4, .height = 4}, kEpsilon},
118+
{{.position = {0.5, 0}, .width = 1, .height = 1}, kEpsilon},
119+
kTravelThreshold),
120+
BrushTipExtrusion::TangentQuality::kNoTangentsFirstContainsSecond);
121+
}
122+
123+
TEST(BrushTipExtrusionTest, EvaluateTangentQualitySecondShapeContainsFirst) {
124+
EXPECT_EQ(BrushTipExtrusion::EvaluateTangentQuality(
125+
{{.position = {0.5, 0}, .width = 1, .height = 1}, kEpsilon},
126+
{{.position = {0, 0}, .width = 4, .height = 4}, kEpsilon},
127+
kTravelThreshold),
128+
BrushTipExtrusion::TangentQuality::kNoTangentsSecondContainsFirst);
129+
}
130+
131+
TEST(BrushTipExtrusionTest,
132+
EvaluateTangentQualityAccountsForFloatingPointPrecision) {
133+
EXPECT_EQ(
134+
BrushTipExtrusion::EvaluateTangentQuality(
135+
{{.position = {1, 2}, .width = 5, .height = 7, .rotation = kPi / 4},
136+
kEpsilon},
137+
{{.position = {1.1818182, 2.1818182},
138+
.width = 5,
139+
.height = 7,
140+
.rotation = kPi / 4},
141+
kEpsilon},
142+
kTravelThreshold),
143+
// Without the offset to the `RoundedPolygon` in `EvaluateTangentQuality`,
144+
// this would be `kBadTangentsJoinedShapeDoesNotCoverInputShapes`, as one
145+
// of the corners of the second shape lies ~1e-7 units outside the joined
146+
// shape due to floating-point precision loss.
147+
BrushTipExtrusion::TangentQuality::kGoodTangents);
148+
}
149+
150+
} // namespace
151+
} // namespace ink::strokes_internal

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