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[Impeller] add support for superellipse. #54562
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| Original file line number | Diff line number | Diff line change |
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| @@ -0,0 +1,111 @@ | ||
| // Copyright 2013 The Flutter Authors. All rights reserved. | ||
| // Use of this source code is governed by a BSD-style license that can be | ||
| // found in the LICENSE file. | ||
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| #include <vector> | ||
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| #include "flutter/impeller/entity/geometry/superellipse_geometry.h" | ||
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| #include "impeller/geometry/constants.h" | ||
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| namespace impeller { | ||
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| SuperellipseGeometry::SuperellipseGeometry(const Point& center, | ||
| Scalar radius, | ||
| Scalar degree, | ||
| Scalar alpha, | ||
| Scalar beta) | ||
| : center_(center), | ||
| degree_(degree), | ||
| radius_(radius), | ||
| alpha_(alpha), | ||
| beta_(beta) {} | ||
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| GeometryResult SuperellipseGeometry::GetPositionBuffer( | ||
| const ContentContext& renderer, | ||
| const Entity& entity, | ||
| RenderPass& pass) const { | ||
| // https://math.stackexchange.com/questions/2573746/superellipse-parametric-equation | ||
| Scalar a = alpha_; | ||
| Scalar b = beta_; | ||
| Scalar n = degree_; | ||
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| // TODO(jonahwilliams): determine parameter values based on scaling factor. | ||
| Scalar step = kPi / 80; | ||
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| // Generate the points for the top left quadrant, and then mirror to the other | ||
| // quadrants. | ||
| std::vector<Point> points; | ||
| points.reserve(41); | ||
| for (int i = 0; i <= 40; i++) { | ||
| Scalar t = i * step; | ||
| Scalar x = a * pow(abs(cos(t)), 2 / n); | ||
| Scalar y = b * pow(abs(sin(t)), 2 / n); | ||
| points.emplace_back(x * radius_, y * radius_); | ||
| } | ||
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There was a problem hiding this comment. Nit: final points are always computed from |
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| static constexpr Point reflection[4] = {{1, 1}, {-1, 1}, {-1, -1}, {1, -1}}; | ||
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| // Reflect into the 4 quadrants and generate the tessellated mesh. The | ||
| // iteration order is reversed so that the trianges are continuous from | ||
| // quadrant to quadrant. | ||
| std::vector<Point> geometry; | ||
| geometry.reserve(1 + 4 * points.size()); | ||
| geometry.push_back(center_); | ||
| for (auto i = 0u; i < points.size(); i++) { | ||
| geometry.push_back(center_ + (reflection[0] * points[i])); | ||
| } | ||
| for (auto i = 0u; i < points.size(); i++) { | ||
| geometry.push_back(center_ + | ||
| (reflection[1] * points[points.size() - i - 1])); | ||
| } | ||
| for (auto i = 0u; i < points.size(); i++) { | ||
| geometry.push_back(center_ + (reflection[2] * points[i])); | ||
| } | ||
| for (auto i = 0u; i < points.size(); i++) { | ||
| geometry.push_back(center_ + | ||
| (reflection[3] * points[points.size() - i - 1])); | ||
| } | ||
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| std::vector<uint16_t> indices; | ||
| indices.reserve(geometry.size() * 3); | ||
| for (auto i = 2u; i < geometry.size(); i++) { | ||
| indices.push_back(0); | ||
| indices.push_back(i - 1); | ||
| indices.push_back(i); | ||
| } | ||
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| auto& host_buffer = renderer.GetTransientsBuffer(); | ||
| return GeometryResult{ | ||
| .type = PrimitiveType::kTriangle, | ||
| .vertex_buffer = | ||
| { | ||
| .vertex_buffer = host_buffer.Emplace( | ||
| geometry.data(), geometry.size() * sizeof(Point), | ||
| alignof(Point)), | ||
| .index_buffer = host_buffer.Emplace( | ||
| indices.data(), indices.size() * sizeof(uint16_t), | ||
| alignof(uint16_t)), | ||
| .vertex_count = indices.size(), | ||
| .index_type = IndexType::k16bit, | ||
| }, | ||
| .transform = entity.GetShaderTransform(pass), | ||
| }; | ||
| } | ||
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| std::optional<Rect> SuperellipseGeometry::GetCoverage( | ||
| const Matrix& transform) const { | ||
| return Rect::MakeOriginSize(center_ - Point(radius_, radius_), | ||
| Size(radius_ * 2, radius_ * 2)); | ||
| } | ||
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| bool SuperellipseGeometry::CoversArea(const Matrix& transform, | ||
| const Rect& rect) const { | ||
| return false; | ||
| } | ||
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| bool SuperellipseGeometry::IsAxisAlignedRect() const { | ||
| return false; | ||
| } | ||
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| } // namespace impeller | ||
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,62 @@ | ||
| // Copyright 2013 The Flutter Authors. All rights reserved. | ||
| // Use of this source code is governed by a BSD-style license that can be | ||
| // found in the LICENSE file. | ||
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| #ifndef FLUTTER_IMPELLER_ENTITY_GEOMETRY_SUPERELLIPSE_GEOMETRY_H_ | ||
| #define FLUTTER_IMPELLER_ENTITY_GEOMETRY_SUPERELLIPSE_GEOMETRY_H_ | ||
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| #include "impeller/entity/geometry/geometry.h" | ||
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| namespace impeller { | ||
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| /// Geometry class that can generate vertices for a superellipse. | ||
| /// | ||
| /// A Superellipse is an ellipse-like shape that is defined by the parameters N, | ||
| /// alpha, and beta: | ||
| /// | ||
| /// 1 = |x / b| ^n + |y / a| ^n | ||
| /// | ||
| /// The radius and center apply a uniform scaling and offset that is separate | ||
| /// from alpha or beta. When n = 4, the shape is referred to as a rectellipse. | ||
| /// | ||
| /// See also: https://en.wikipedia.org/wiki/Superellipse | ||
| class SuperellipseGeometry final : public Geometry { | ||
| public: | ||
| explicit SuperellipseGeometry(const Point& center, | ||
| Scalar radius, | ||
| Scalar degree, | ||
| Scalar alpha, | ||
| Scalar beta); | ||
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| ~SuperellipseGeometry() = default; | ||
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| // |Geometry| | ||
| bool CoversArea(const Matrix& transform, const Rect& rect) const override; | ||
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| // |Geometry| | ||
| bool IsAxisAlignedRect() const override; | ||
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| private: | ||
| // |Geometry| | ||
| GeometryResult GetPositionBuffer(const ContentContext& renderer, | ||
| const Entity& entity, | ||
| RenderPass& pass) const override; | ||
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| // |Geometry| | ||
| std::optional<Rect> GetCoverage(const Matrix& transform) const override; | ||
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| Point center_; | ||
| // 4 is a rectellipse | ||
| Scalar degree_; | ||
| Scalar radius_; | ||
| Scalar alpha_; | ||
| Scalar beta_; | ||
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| SuperellipseGeometry(const SuperellipseGeometry&) = delete; | ||
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| SuperellipseGeometry& operator=(const SuperellipseGeometry&) = delete; | ||
| }; | ||
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| } // namespace impeller | ||
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| #endif // FLUTTER_IMPELLER_ENTITY_GEOMETRY_SUPERELLIPSE_GEOMETRY_H_ |
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Putting this part in the Tessellator would allow it to leverage the "GetTrigsForDivisions" caching.
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I'm going to leave this out for now so its stays separate before we decide how to ship it, but I agree it should eventually live in the tessellator.
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Good call if it isolates it until we figure out its future. It will matter a little for benchmarks, but not for testing its usefulness.