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[Impeller] Add direct tesselation of circles for DrawCircle and Round end caps #48103

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Nov 30, 2023
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[Impeller] Add direct tesselation of circles for DrawCircle and Round end caps #48103

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72d57eb
[Impeller] Add direct tesselation of circles for DrawCircle and Round…
flar Nov 16, 2023
63ea32b
switch to triangle strips for circles and simplify tessellation API
flar Nov 17, 2023
d498124
Fix old naming typos in comments
flar Nov 17, 2023
cab69d8
simplify vertex accumulation
flar Nov 22, 2023
cfca2e1
re-enable GPU compute tessellator for PointFields
flar Nov 22, 2023
4b638ba
move to direct HostBuffer emplacement of tessellation results
flar Nov 22, 2023
4ccdb46
Move CircleTessellator to tessellator dir and move cache to Tessellat…
flar Nov 30, 2023
aeef542
document and refine circle division computation
flar Nov 30, 2023
16fa52d
style feedback from review
flar Nov 30, 2023
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simplify vertex accumulation
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@flar
flar committed Nov 30, 2023
commit cab69d8f98f81968585632207c2226c6afe70a01
38 changes: 16 additions & 22 deletions impeller/entity/geometry/ellipse_geometry.cc
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Original file line number Diff line number Diff line change
Expand Up @@ -19,21 +19,19 @@ GeometryResult EllipseGeometry::GetPositionBuffer(
RenderPass& pass) const {
auto& host_buffer = pass.GetTransientsBuffer();

VertexBufferBuilder<SolidFillVertexShader::PerVertexData> vtx_builder;

CircleTessellator tessellator(entity.GetTransform(), radius_);
auto vertices = std::vector<Point>(tessellator.GetCircleVertexCount());
vtx_builder.Reserve(tessellator.GetCircleVertexCount());
tessellator.GenerateCircleTriangleStrip(
[&vertices](const Point& p) { vertices.push_back(p); }, center_, radius_);
[&vtx_builder](const Point& p) { //
vtx_builder.AppendVertex({.position = p});
},
center_, radius_);

return GeometryResult{
.type = PrimitiveType::kTriangleStrip,
.vertex_buffer =
{
.vertex_buffer = host_buffer.Emplace(
vertices.data(), vertices.size() * sizeof(Point),
alignof(float)),
.vertex_count = vertices.size(),
.index_type = IndexType::kNone,
},
.vertex_buffer = vtx_builder.CreateVertexBuffer(host_buffer),
.transform = Matrix::MakeOrthographic(pass.GetRenderTargetSize()) *
entity.GetTransform(),
.prevent_overdraw = false,
Expand All @@ -51,26 +49,22 @@ GeometryResult EllipseGeometry::GetPositionUVBuffer(

auto uv_transform =
texture_coverage.GetNormalizingTransform() * effect_transform;
VertexBufferBuilder<TextureFillVertexShader::PerVertexData> vtx_builder;

CircleTessellator tessellator(entity.GetTransform(), radius_);
auto vertices = std::vector<Point>(tessellator.GetCircleVertexCount());
vtx_builder.Reserve(tessellator.GetCircleVertexCount());
tessellator.GenerateCircleTriangleStrip(
[&vertices, &uv_transform](const Point& p) {
vertices.push_back(p);
vertices.push_back(uv_transform * p);
[&vtx_builder, &uv_transform](const Point& p) {
vtx_builder.AppendVertex({
.position = p,
.texture_coords = uv_transform * p,
});
},
center_, radius_);

return GeometryResult{
.type = PrimitiveType::kTriangleStrip,
.vertex_buffer =
{
.vertex_buffer = host_buffer.Emplace(
vertices.data(), vertices.size() * sizeof(Point),
alignof(float)),
.vertex_count = vertices.size() / 2,
.index_type = IndexType::kNone,
},
.vertex_buffer = vtx_builder.CreateVertexBuffer(host_buffer),
.transform = Matrix::MakeOrthographic(pass.GetRenderTargetSize()) *
entity.GetTransform(),
.prevent_overdraw = false,
Expand Down
71 changes: 28 additions & 43 deletions impeller/entity/geometry/line_geometry.cc
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Original file line number Diff line number Diff line change
Expand Up @@ -68,44 +68,37 @@ bool LineGeometry::ComputeCorners(Point corners[4],
GeometryResult LineGeometry::GetPositionBuffer(const ContentContext& renderer,
const Entity& entity,
RenderPass& pass) const {
std::vector<Point> vertices;
auto& transform = entity.GetTransform();
auto radius = ComputeHalfWidth(transform);

VertexBufferBuilder<SolidFillVertexShader::PerVertexData> vtx_builder;

if (cap_ == Cap::kRound) {
CircleTessellator tessellator(transform, radius);
vertices.reserve(tessellator.GetCircleVertexCount());
vtx_builder.Reserve(tessellator.GetCircleVertexCount());
tessellator.GenerateRoundCapLineTriangleStrip(
[&vertices](const Point& p) { //
vertices.push_back(p);
[&vtx_builder](const Point& p) { //
vtx_builder.AppendVertex({.position = p});
},
p0_, p1_, radius);
} else {
Point corners[4];
if (ComputeCorners(corners, transform, cap_ == Cap::kSquare)) {
vertices.reserve(4);
vertices.push_back(corners[0]);
vertices.push_back(corners[1]);
vertices.push_back(corners[2]);
vertices.push_back(corners[3]);
vtx_builder.Reserve(4);
vtx_builder.AppendVertex({.position = corners[0]});
vtx_builder.AppendVertex({.position = corners[1]});
vtx_builder.AppendVertex({.position = corners[2]});
vtx_builder.AppendVertex({.position = corners[3]});
}
}
if (vertices.empty()) {
if (!vtx_builder.HasVertices()) {
return {};
}

static_assert(sizeof(Point) == 2 * sizeof(float));
static_assert(alignof(Point) == alignof(float));
return GeometryResult{
.type = PrimitiveType::kTriangleStrip,
.vertex_buffer =
{
.vertex_buffer = pass.GetTransientsBuffer().Emplace(
vertices.data(), vertices.size() * sizeof(Point),
alignof(Point)),
.vertex_count = vertices.size(),
.index_type = IndexType::kNone,
},
vtx_builder.CreateVertexBuffer(pass.GetTransientsBuffer()),
.transform = Matrix::MakeOrthographic(pass.GetRenderTargetSize()) *
entity.GetTransform(),
.prevent_overdraw = false,
Expand All @@ -118,52 +111,44 @@ GeometryResult LineGeometry::GetPositionUVBuffer(Rect texture_coverage,
const ContentContext& renderer,
const Entity& entity,
RenderPass& pass) const {
std::vector<Point> vertices;
auto& transform = entity.GetTransform();
auto radius = ComputeHalfWidth(transform);

auto uv_transform =
texture_coverage.GetNormalizingTransform() * effect_transform;
VertexBufferBuilder<TextureFillVertexShader::PerVertexData> vtx_builder;

if (cap_ == Cap::kRound) {
CircleTessellator tessellator(transform, radius);
vertices.reserve(tessellator.GetCircleVertexCount() * 2);
vtx_builder.Reserve(tessellator.GetCircleVertexCount());
tessellator.GenerateRoundCapLineTriangleStrip(
[&vertices, &uv_transform](const Point& p) {
vertices.push_back(p);
vertices.push_back(uv_transform * p);
[&vtx_builder, &uv_transform](const Point& p) {
vtx_builder.AppendVertex({
.position = p,
.texture_coords = uv_transform * p,
});
},
p0_, p1_, radius);
} else {
Point corners[4];
if (ComputeCorners(corners, transform, cap_ == Cap::kSquare)) {
vertices.reserve(8);
vertices.push_back(corners[0]);
vertices.push_back(uv_transform * corners[0]);
vertices.push_back(corners[1]);
vertices.push_back(uv_transform * corners[1]);
vertices.push_back(corners[2]);
vertices.push_back(uv_transform * corners[2]);
vertices.push_back(corners[3]);
vertices.push_back(uv_transform * corners[3]);
vtx_builder.Reserve(4);
for (auto& corner : corners) {
vtx_builder.AppendVertex({
.position = corner,
.texture_coords = uv_transform * corner,
});
}
}
}
if (vertices.empty()) {
if (!vtx_builder.HasVertices()) {
return {};
}

static_assert(sizeof(Point) == 2 * sizeof(float));
static_assert(alignof(Point) == alignof(float));
return GeometryResult{
.type = PrimitiveType::kTriangleStrip,
.vertex_buffer =
{
.vertex_buffer = pass.GetTransientsBuffer().Emplace(
vertices.data(), vertices.size() * sizeof(Point),
alignof(Point)),
.vertex_count = vertices.size() / 2,
.index_type = IndexType::kNone,
},
vtx_builder.CreateVertexBuffer(pass.GetTransientsBuffer()),
.transform = Matrix::MakeOrthographic(pass.GetRenderTargetSize()) *
entity.GetTransform(),
.prevent_overdraw = false,
Expand Down
49 changes: 22 additions & 27 deletions impeller/entity/geometry/point_field_geometry.cc
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Original file line number Diff line number Diff line change
Expand Up @@ -87,48 +87,43 @@ PointFieldGeometry::GetPositionBufferCPU(const ContentContext& renderer,
if (round_) {
CircleTessellator tessellator(entity.GetTransform(), radius);

// Get polygon relative to {0, 0} so we can translate it to each point
// in turn.
std::vector<Point> vertices;
// Get triangulation relative to {0, 0} so we can translate it to each
// point in turn.
std::vector<Point> circle_vertices;
circle_vertices.reserve(tessellator.GetCircleVertexCount());
tessellator.GenerateCircleTriangleStrip(
[&vertices](const Point& p) { //
vertices.push_back(p);
[&circle_vertices](const Point& p) { //
circle_vertices.push_back(p);
},
{}, radius);
FML_DCHECK(vertices.size() == tessellator.GetCircleVertexCount());
vtx_builder.Reserve(vertices.size() * points_.size());
FML_DCHECK(circle_vertices.size() == tessellator.GetCircleVertexCount());

bool first = true;
Point prev;
vtx_builder.Reserve((circle_vertices.size() + 2) * points_.size() - 2);
for (auto& center : points_) {
if (first) {
first = false;
} else {
vtx_builder.AppendVertex({prev});
vtx_builder.AppendVertex({center + vertices[0]});
if (vtx_builder.HasVertices()) {
vtx_builder.AppendVertex(vtx_builder.Last());
vtx_builder.AppendVertex({center + circle_vertices[0]});
}
for (auto& vertex : vertices) {
prev = center + vertex;
vtx_builder.AppendVertex({prev});

for (auto& vertex : circle_vertices) {
vtx_builder.AppendVertex({center + vertex});
}
}
} else {
vtx_builder.Reserve(6 * points_.size());
bool first = true;
Point prev;
vtx_builder.Reserve(6 * points_.size() - 2);
for (auto& point : points_) {
if (first) {
first = false;
} else {
vtx_builder.AppendVertex({prev});
vtx_builder.AppendVertex({{point.x - radius, point.y - radius}});
auto first = Point(point.x - radius, point.y - radius);

if (vtx_builder.HasVertices()) {
vtx_builder.AppendVertex(vtx_builder.Last());
vtx_builder.AppendVertex({first});
}

// Z pattern from UL -> UR -> LL -> LR
vtx_builder.AppendVertex({{point.x - radius, point.y - radius}});
vtx_builder.AppendVertex({first});
vtx_builder.AppendVertex({{point.x + radius, point.y - radius}});
vtx_builder.AppendVertex({{point.x - radius, point.y + radius}});
vtx_builder.AppendVertex({prev = {point.x + radius, point.y + radius}});
vtx_builder.AppendVertex({{point.x + radius, point.y + radius}});
}
}

Expand Down
5 changes: 5 additions & 0 deletions impeller/renderer/vertex_buffer_builder.h
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Original file line number Diff line number Diff line change
Expand Up @@ -56,6 +56,11 @@ class VertexBufferBuilder {
return indices_.size() > 0 ? indices_.size() : vertices_.size();
}

const VertexType& Last() const {
FML_DCHECK(!vertices_.empty());
return vertices_.back();
}

VertexBufferBuilder& AppendVertex(VertexType_ vertex) {
vertices_.emplace_back(std::move(vertex));
return *this;
Expand Down