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Draw stroked circles with round caps analytically.

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These draw as the butt cap version where the stroked circle is clipped by half planes. But then we add in coverage from circles at the caps.

Bug: skia:7793
Change-Id: I7c27a2a5f1f9c1645cc9042e68e787dd81ea28b8
Reviewed-on: https://skia-review.googlesource.com/120140
Commit-Queue: Brian Salomon <bsalomon@google.com>
Reviewed-by: Jim Van Verth <jvanverth@google.com>
This commit is contained in:
Brian Salomon 2018-04-10 10:53:58 -04:00 committed by Skia Commit-Bot
parent cf1ac58e24
commit 45c92203ef
1 changed files with 115 additions and 21 deletions
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136
src/gpu/ops/GrOvalOpFactory.cpp
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@ -62,14 +62,17 @@ static inline bool circle_stays_circle(const SkMatrix& m) { return m.isSimilarit
* a plane intersected with the initial plane, and a plane unioned with the first two). Only two
* are useful for any given arc, but having all three in one instance allows combining different
* types of arcs.
* Round caps for stroking are allowed as well. The caps are specified as two circle center points
* in the same space as p.xy.
*/
class CircleGeometryProcessor : public GrGeometryProcessor {
public:
CircleGeometryProcessor(bool stroke, bool clipPlane, bool isectPlane, bool unionPlane,
const SkMatrix& localMatrix)
bool roundCaps, const SkMatrix& localMatrix)
: INHERITED(kCircleGeometryProcessor_ClassID)
, fLocalMatrix(localMatrix) {
, fLocalMatrix(localMatrix)
, fStroke(stroke) {
fInPosition = &this->addVertexAttrib("inPosition", kFloat2_GrVertexAttribType);
fInColor = &this->addVertexAttrib("inColor", kUByte4_norm_GrVertexAttribType);
fInCircleEdge = &this->addVertexAttrib("inCircleEdge", kFloat4_GrVertexAttribType);
@ -88,7 +91,14 @@ public:
} else {
fInUnionPlane = nullptr;
}
fStroke = stroke;
if (roundCaps) {
SkASSERT(stroke);
SkASSERT(clipPlane);
fInRoundCapCenters =
&this->addVertexAttrib("inRoundCapCenters", kFloat4_GrVertexAttribType);
} else {
fInRoundCapCenters = nullptr;
}
}
~CircleGeometryProcessor() override {}
@ -133,6 +143,17 @@ private:
fragBuilder->codeAppend("half3 unionPlane;");
varyingHandler->addPassThroughAttribute(cgp.fInUnionPlane, "unionPlane");
}
GrGLSLVarying capRadius(kFloat_GrSLType);
if (cgp.fInRoundCapCenters) {
fragBuilder->codeAppend("float4 roundCapCenters;");
varyingHandler->addPassThroughAttribute(cgp.fInRoundCapCenters, "roundCapCenters");
varyingHandler->addVarying("capRadius", &capRadius,
GrGLSLVaryingHandler::Interpolation::kCanBeFlat);
// This is the cap radius in normalized space where the outer radius is 1 and
// circledEdge.w is the normalized inner radius.
vertBuilder->codeAppendf("%s = (1.0 - %s.w) / 2.0;", capRadius.vsOut(),
cgp.fInCircleEdge->fName);
}
// setup pass through color
varyingHandler->addPassThroughAttribute(cgp.fInColor, args.fOutputColor);
@ -173,6 +194,16 @@ private:
"unionPlane.xy) + unionPlane.z, 0.0, 1.0);");
}
fragBuilder->codeAppend("edgeAlpha *= clip;");
if (cgp.fInRoundCapCenters) {
fragBuilder->codeAppendf(
"half dcap1 = circleEdge.z * (%s - length(circleEdge.xy - "
" roundCapCenters.xy));"
"half dcap2 = circleEdge.z * (%s - length(circleEdge.xy - "
" roundCapCenters.zw));"
"half capAlpha = max(dcap1, 0) + max(dcap2, 0);"
"edgeAlpha = min(edgeAlpha + capAlpha, 1.0);",
capRadius.fsIn(), capRadius.fsIn());
}
}
fragBuilder->codeAppendf("%s = half4(edgeAlpha);", args.fOutputCoverage);
}
@ -187,6 +218,7 @@ private:
key |= cgp.fInClipPlane ? 0x04 : 0x0;
key |= cgp.fInIsectPlane ? 0x08 : 0x0;
key |= cgp.fInUnionPlane ? 0x10 : 0x0;
key |= cgp.fInRoundCapCenters ? 0x20 : 0x0;
b->add32(key);
}
@ -207,8 +239,8 @@ private:
const Attribute* fInClipPlane;
const Attribute* fInIsectPlane;
const Attribute* fInUnionPlane;
const Attribute* fInRoundCapCenters;
bool fStroke;
GR_DECLARE_GEOMETRY_PROCESSOR_TEST
typedef GrGeometryProcessor INHERITED;
@ -218,9 +250,14 @@ GR_DEFINE_GEOMETRY_PROCESSOR_TEST(CircleGeometryProcessor);
#if GR_TEST_UTILS
sk_sp<GrGeometryProcessor> CircleGeometryProcessor::TestCreate(GrProcessorTestData* d) {
return sk_sp<GrGeometryProcessor>(new CircleGeometryProcessor(
d->fRandom->nextBool(), d->fRandom->nextBool(), d->fRandom->nextBool(),
d->fRandom->nextBool(), GrTest::TestMatrix(d->fRandom)));
bool stroke = d->fRandom->nextBool();
bool roundCaps = stroke ? d->fRandom->nextBool() : false;
bool clipPlane = d->fRandom->nextBool();
bool isectPlane = d->fRandom->nextBool();
bool unionPlane = d->fRandom->nextBool();
const SkMatrix& matrix = GrTest::TestMatrix(d->fRandom);
return sk_sp<GrGeometryProcessor>(new CircleGeometryProcessor(stroke, roundCaps, clipPlane,
isectPlane, unionPlane, matrix));
}
#endif
@ -609,9 +646,16 @@ public:
case SkStrokeRec::kFill_Style:
// This supports all fills.
break;
case SkStrokeRec::kStroke_Style: // fall through
case SkStrokeRec::kStroke_Style:
// Strokes that don't use the center point are supported with butt and round
// caps.
if (arcParams->fUseCenter || stroke.getCap() == SkPaint::kSquare_Cap) {
return nullptr;
}
break;
case SkStrokeRec::kHairline_Style:
// Strokes that don't use the center point are supported with butt cap.
// Hairline only supports butt cap. Round caps could be emulated by slightly
// extending the angle range if we ever care to.
if (arcParams->fUseCenter || stroke.getCap() != SkPaint::kButt_Cap) {
return nullptr;
}
@ -628,6 +672,8 @@ public:
const SkStrokeRec& stroke = style.strokeRec();
SkStrokeRec::Style recStyle = stroke.getStyle();
fRoundCaps = false;
viewMatrix.mapPoints(&center, 1);
radius = viewMatrix.mapRadius(radius);
SkScalar strokeWidth = viewMatrix.mapRadius(stroke.getWidth());
@ -665,6 +711,7 @@ public:
static constexpr SkScalar kUnusedIsectPlane[] = {0.f, 0.f, 1.f};
// This makes every point fully outside the union plane.
static constexpr SkScalar kUnusedUnionPlane[] = {0.f, 0.f, 0.f};
static constexpr SkPoint kUnusedRoundCaps[] = {{1e10f, 1e10f}, {1e10f, 1e10f}};
SkRect devBounds = SkRect::MakeLTRB(center.fX - outerRadius, center.fY - outerRadius,
center.fX + outerRadius, center.fY + outerRadius);
if (arcParams) {
@ -686,14 +733,29 @@ public:
SkTSwap(startPoint, stopPoint);
}
fRoundCaps = style.strokeRec().getWidth() > 0 &&
style.strokeRec().getCap() == SkPaint::kRound_Cap;
SkPoint roundCaps[2];
if (fRoundCaps) {
// Compute the cap center points in the normalized space.
SkScalar midRadius = (innerRadius + outerRadius) / (2 * outerRadius);
roundCaps[0] = startPoint * midRadius;
roundCaps[1] = stopPoint * midRadius;
} else {
roundCaps[0] = kUnusedRoundCaps[0];
roundCaps[1] = kUnusedRoundCaps[1];
}
// Like a fill without useCenter, butt-cap stroke can be implemented by clipping against
// radial lines. However, in both cases we have to be careful about the half-circle.
// radial lines. We treat round caps the same way, but tack coverage of circles at the
// center of the butts.
// However, in both cases we have to be careful about the half-circle.
// case. In that case the two radial lines are equal and so that edge gets clipped
// twice. Since the shared edge goes through the center we fall back on the useCenter
// twice. Since the shared edge goes through the center we fall back on the !useCenter
// case.
bool useCenter =
(arcParams->fUseCenter || isStrokeOnly) &&
!SkScalarNearlyEqual(SkScalarAbs(arcParams->fSweepAngleRadians), SK_ScalarPI);
auto absSweep = SkScalarAbs(arcParams->fSweepAngleRadians);
bool useCenter = (arcParams->fUseCenter || isStrokeOnly) &&
!SkScalarNearlyEqual(absSweep, SK_ScalarPI);
if (useCenter) {
SkVector norm0 = {startPoint.fY, -startPoint.fX};
SkVector norm1 = {stopPoint.fY, -stopPoint.fX};
@ -703,7 +765,7 @@ public:
norm1.negate();
}
fClipPlane = true;
if (SkScalarAbs(arcParams->fSweepAngleRadians) > SK_ScalarPI) {
if (absSweep > SK_ScalarPI) {
fCircles.emplace_back(Circle{
color,
innerRadius,
@ -711,6 +773,7 @@ public:
{norm0.fX, norm0.fY, 0.5f},
{kUnusedIsectPlane[0], kUnusedIsectPlane[1], kUnusedIsectPlane[2]},
{norm1.fX, norm1.fY, 0.5f},
{roundCaps[0], roundCaps[1]},
devBounds,
stroked});
fClipPlaneIsect = false;
@ -723,6 +786,7 @@ public:
{norm0.fX, norm0.fY, 0.5f},
{norm1.fX, norm1.fY, 0.5f},
{kUnusedUnionPlane[0], kUnusedUnionPlane[1], kUnusedUnionPlane[2]},
{roundCaps[0], roundCaps[1]},
devBounds,
stroked});
fClipPlaneIsect = true;
@ -746,6 +810,7 @@ public:
{norm.fX, norm.fY, d},
{kUnusedIsectPlane[0], kUnusedIsectPlane[1], kUnusedIsectPlane[2]},
{kUnusedUnionPlane[0], kUnusedUnionPlane[1], kUnusedUnionPlane[2]},
{roundCaps[0], roundCaps[1]},
devBounds,
stroked});
fClipPlane = true;
@ -760,6 +825,7 @@ public:
{kUnusedIsectPlane[0], kUnusedIsectPlane[1], kUnusedIsectPlane[2]},
{kUnusedIsectPlane[0], kUnusedIsectPlane[1], kUnusedIsectPlane[2]},
{kUnusedUnionPlane[0], kUnusedUnionPlane[1], kUnusedUnionPlane[2]},
{kUnusedRoundCaps[0], kUnusedRoundCaps[1]},
devBounds,
stroked});
fClipPlane = false;
@ -816,7 +882,7 @@ private:
// Setup geometry processor
sk_sp<GrGeometryProcessor> gp(new CircleGeometryProcessor(
!fAllFill, fClipPlane, fClipPlaneIsect, fClipPlaneUnion, localMatrix));
!fAllFill, fClipPlane, fClipPlaneIsect, fClipPlaneUnion, fRoundCaps, localMatrix));
struct CircleVertex {
SkPoint fPos;
@ -828,11 +894,15 @@ private:
SkScalar fHalfPlanes[3][3];
};
int numPlanes = (int)fClipPlane + fClipPlaneIsect + fClipPlaneUnion;
auto vertexCapCenters = [numPlanes](CircleVertex* v) {
return (void*)(v->fHalfPlanes + numPlanes);
};
size_t vertexStride = gp->getVertexStride();
SkASSERT(vertexStride ==
sizeof(CircleVertex) - (fClipPlane ? 0 : 3 * sizeof(SkScalar)) -
(fClipPlaneIsect ? 0 : 3 * sizeof(SkScalar)) -
(fClipPlaneUnion ? 0 : 3 * sizeof(SkScalar)));
SkASSERT(vertexStride == sizeof(CircleVertex) - (fClipPlane ? 0 : 3 * sizeof(SkScalar)) -
(fClipPlaneIsect ? 0 : 3 * sizeof(SkScalar)) -
(fClipPlaneUnion ? 0 : 3 * sizeof(SkScalar)) +
(fRoundCaps ? 2 * sizeof(SkPoint) : 0));
const GrBuffer* vertexBuffer;
int firstVertex;
@ -954,6 +1024,16 @@ private:
memcpy(v6->fHalfPlanes[unionIdx], circle.fUnionPlane, 3 * sizeof(SkScalar));
memcpy(v7->fHalfPlanes[unionIdx], circle.fUnionPlane, 3 * sizeof(SkScalar));
}
if (fRoundCaps) {
memcpy(vertexCapCenters(v0), circle.fRoundCapCenters, 2 * sizeof(SkPoint));
memcpy(vertexCapCenters(v1), circle.fRoundCapCenters, 2 * sizeof(SkPoint));
memcpy(vertexCapCenters(v2), circle.fRoundCapCenters, 2 * sizeof(SkPoint));
memcpy(vertexCapCenters(v3), circle.fRoundCapCenters, 2 * sizeof(SkPoint));
memcpy(vertexCapCenters(v4), circle.fRoundCapCenters, 2 * sizeof(SkPoint));
memcpy(vertexCapCenters(v5), circle.fRoundCapCenters, 2 * sizeof(SkPoint));
memcpy(vertexCapCenters(v6), circle.fRoundCapCenters, 2 * sizeof(SkPoint));
memcpy(vertexCapCenters(v7), circle.fRoundCapCenters, 2 * sizeof(SkPoint));
}
if (circle.fStroked) {
// compute the inner ring
@ -1051,6 +1131,16 @@ private:
memcpy(v6->fHalfPlanes[unionIdx], circle.fUnionPlane, 3 * sizeof(SkScalar));
memcpy(v7->fHalfPlanes[unionIdx], circle.fUnionPlane, 3 * sizeof(SkScalar));
}
if (fRoundCaps) {
memcpy(vertexCapCenters(v0), circle.fRoundCapCenters, 2 * sizeof(SkPoint));
memcpy(vertexCapCenters(v1), circle.fRoundCapCenters, 2 * sizeof(SkPoint));
memcpy(vertexCapCenters(v2), circle.fRoundCapCenters, 2 * sizeof(SkPoint));
memcpy(vertexCapCenters(v3), circle.fRoundCapCenters, 2 * sizeof(SkPoint));
memcpy(vertexCapCenters(v4), circle.fRoundCapCenters, 2 * sizeof(SkPoint));
memcpy(vertexCapCenters(v5), circle.fRoundCapCenters, 2 * sizeof(SkPoint));
memcpy(vertexCapCenters(v6), circle.fRoundCapCenters, 2 * sizeof(SkPoint));
memcpy(vertexCapCenters(v7), circle.fRoundCapCenters, 2 * sizeof(SkPoint));
}
} else {
// filled
CircleVertex* v8 = reinterpret_cast<CircleVertex*>(vertices + 8 * vertexStride);
@ -1070,6 +1160,7 @@ private:
if (fClipPlaneUnion) {
memcpy(v8->fHalfPlanes[unionIdx], circle.fUnionPlane, 3 * sizeof(SkScalar));
}
SkASSERT(!fRoundCaps);
}
const uint16_t* primIndices = circle_type_to_indices(circle.fStroked);
@ -1110,6 +1201,7 @@ private:
fClipPlane |= that->fClipPlane;
fClipPlaneIsect |= that->fClipPlaneIsect;
fClipPlaneUnion |= that->fClipPlaneUnion;
fRoundCaps |= that->fRoundCaps;
fCircles.push_back_n(that->fCircles.count(), that->fCircles.begin());
this->joinBounds(*that);
@ -1126,6 +1218,7 @@ private:
SkScalar fClipPlane[3];
SkScalar fIsectPlane[3];
SkScalar fUnionPlane[3];
SkPoint fRoundCapCenters[2];
SkRect fDevBounds;
bool fStroked;
};
@ -1139,6 +1232,7 @@ private:
bool fClipPlane;
bool fClipPlaneIsect;
bool fClipPlaneUnion;
bool fRoundCaps;
typedef GrMeshDrawOp INHERITED;
};
@ -1921,7 +2015,7 @@ private:
// Setup geometry processor
sk_sp<GrGeometryProcessor> gp(
new CircleGeometryProcessor(!fAllFill, false, false, false, localMatrix));
new CircleGeometryProcessor(!fAllFill, false, false, false, false, localMatrix));
size_t vertexStride = gp->getVertexStride();
SkASSERT(sizeof(CircleVertex) == vertexStride);