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/*
* Copyright 2022 Google LLC
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
#ifndef INK_STROKE_MODELER_INTERNAL_UTILS_H_
#define INK_STROKE_MODELER_INTERNAL_UTILS_H_
#include <cmath>
#include "ink_stroke_modeler/types.h"
namespace ink {
namespace stroke_model {
// General utility functions for use within the stroke model.
// Clamps the given value to the range [0, 1].
inline float Clamp01(float value) {
if (value < 0.f) return 0.f;
if (value > 1.f) return 1.f;
return value;
}
// Returns the ratio of the difference from `start` to `value` and the
// difference from `start` to `end`, clamped to the range [0, 1]. If
// `start` == `end`, returns 1 if `value` > `start`, 0 otherwise.
inline float Normalize01(float start, float end, float value) {
if (start == end) {
return value > start ? 1 : 0;
}
return Clamp01((value - start) / (end - start));
}
// Linearly interpolates between `start` and `end`, clamping the interpolation
// value to the range [0, 1].
template <typename ValueType>
inline ValueType Interp(ValueType start, ValueType end, float interp_amount) {
return start + (end - start) * Clamp01(interp_amount);
}
// Linearly interpolates from `start` to `end`, traveling around the shorter
// path (e.g. interpolating from π/4 to 7π/4 is equivalent to interpolating from
// π/4 to 0, then 2π to 7π/4). The returned angle will be normalized to the
// interval [0, 2π). All angles are measured in radians.
inline float InterpAngle(float start, float end, float interp_amount) {
auto normalize_angle = [](float angle) {
while (angle < 0) angle += 2 * M_PI;
while (angle > 2 * M_PI) angle -= 2 * M_PI;
return angle;
};
start = normalize_angle(start);
end = normalize_angle(end);
float delta = end - start;
if (delta < -M_PI) {
end += 2 * M_PI;
} else if (delta > M_PI) {
end -= 2 * M_PI;
}
return normalize_angle(Interp(start, end, interp_amount));
}
// Returns the distance between two points.
inline float Distance(Vec2 start, Vec2 end) {
return (end - start).Magnitude();
}
// Returns the point on the line segment from `segment_start` to `segment_end`
// that is closest to `point`, represented as the ratio of the length along the
// segment.
inline float NearestPointOnSegment(Vec2 segment_start, Vec2 segment_end,
Vec2 point) {
if (segment_start == segment_end) return 0;
auto dot_product = [](Vec2 lhs, Vec2 rhs) {
return lhs.x * rhs.x + lhs.y * rhs.y;
};
Vec2 segment_vector = segment_end - segment_start;
Vec2 projection_vector = point - segment_start;
return Clamp01(dot_product(projection_vector, segment_vector) /
dot_product(segment_vector, segment_vector));
}
} // namespace stroke_model
} // namespace ink
#endif // INK_STROKE_MODELER_INTERNAL_UTILS_H_
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