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- /*
- * Copyright 2019 Google Inc.
- *
- * Use of this source code is governed by a BSD-style license that can be
- * found in the LICENSE file.
- */
- #include "samplecode/Sample.h"
- #include "src/gpu/geometry/GrQuad.h"
- #include "src/gpu/ops/GrQuadPerEdgeAA.h"
- #include "include/core/SkCanvas.h"
- #include "include/core/SkPaint.h"
- #include "include/effects/SkDashPathEffect.h"
- #include "include/pathops/SkPathOps.h"
- // Draw a line through the two points, outset by a fixed length in screen space
- static void draw_extended_line(SkCanvas* canvas, const SkPaint paint,
- const SkPoint& p0, const SkPoint& p1) {
- SkVector v = p1 - p0;
- v.setLength(v.length() + 3.f);
- canvas->drawLine(p1 - v, p0 + v, paint);
- // Draw normal vector too
- SkPaint normalPaint = paint;
- normalPaint.setPathEffect(nullptr);
- normalPaint.setStrokeWidth(paint.getStrokeWidth() / 4.f);
- SkVector n = {v.fY, -v.fX};
- n.setLength(.25f);
- SkPoint m = (p0 + p1) * 0.5f;
- canvas->drawLine(m, m + n, normalPaint);
- }
- static void make_aa_line(const SkPoint& p0, const SkPoint& p1, bool aaOn,
- bool outset, SkPoint line[2]) {
- SkVector n = {0.f, 0.f};
- if (aaOn) {
- SkVector v = p1 - p0;
- n = outset ? SkVector::Make(v.fY, -v.fX) : SkVector::Make(-v.fY, v.fX);
- n.setLength(0.5f);
- }
- line[0] = p0 + n;
- line[1] = p1 + n;
- }
- // To the line through l0-l1, not capped at the end points of the segment
- static SkScalar signed_distance(const SkPoint& p, const SkPoint& l0, const SkPoint& l1) {
- SkVector v = l1 - l0;
- v.normalize();
- SkVector n = {v.fY, -v.fX};
- SkScalar c = -n.dot(l0);
- return n.dot(p) + c;
- }
- static SkScalar get_area_coverage(const bool edgeAA[4], const SkPoint corners[4],
- const SkPoint& point) {
- SkPath shape;
- shape.addPoly(corners, 4, true);
- SkPath pixel;
- pixel.addRect(SkRect::MakeXYWH(point.fX - 0.5f, point.fY - 0.5f, 1.f, 1.f));
- SkPath intersection;
- if (!Op(shape, pixel, kIntersect_SkPathOp, &intersection) || intersection.isEmpty()) {
- return 0.f;
- }
- // Calculate area of the convex polygon
- SkScalar area = 0.f;
- for (int i = 0; i < intersection.countPoints(); ++i) {
- SkPoint p0 = intersection.getPoint(i);
- SkPoint p1 = intersection.getPoint((i + 1) % intersection.countPoints());
- SkScalar det = p0.fX * p1.fY - p1.fX * p0.fY;
- area += det;
- }
- // Scale by 1/2, then take abs value (this area formula is signed based on point winding, but
- // since it's convex, just make it positive).
- area = SkScalarAbs(0.5f * area);
- // Now account for the edge AA. If the pixel center is outside of a non-AA edge, turn of its
- // coverage. If the pixel only intersects non-AA edges, then set coverage to 1.
- bool needsNonAA = false;
- SkScalar edgeD[4];
- for (int i = 0; i < 4; ++i) {
- SkPoint e0 = corners[i];
- SkPoint e1 = corners[(i + 1) % 4];
- edgeD[i] = -signed_distance(point, e0, e1);
- if (!edgeAA[i]) {
- if (edgeD[i] < -1e-4f) {
- return 0.f; // Outside of non-AA line
- }
- needsNonAA = true;
- }
- }
- // Otherwise inside the shape, so check if any AA edge exerts influence over nonAA
- if (needsNonAA) {
- for (int i = 0; i < 4; i++) {
- if (edgeAA[i] && edgeD[i] < 0.5f) {
- needsNonAA = false;
- break;
- }
- }
- }
- return needsNonAA ? 1.f : area;
- }
- // FIXME take into account max coverage properly,
- static SkScalar get_edge_dist_coverage(const bool edgeAA[4], const SkPoint corners[4],
- const SkPoint outsetLines[8], const SkPoint insetLines[8],
- const SkPoint& point) {
- bool flip = false;
- // If the quad has been inverted, the original corners will not all be on the negative side of
- // every outset line. When that happens, calculate coverage using the "inset" lines and flip
- // the signed distance
- for (int i = 0; i < 4; ++i) {
- for (int j = 0; j < 4; ++j) {
- SkScalar d = signed_distance(corners[i], outsetLines[j * 2], outsetLines[j * 2 + 1]);
- if (d > 1e-4f) {
- flip = true;
- break;
- }
- }
- if (flip) {
- break;
- }
- }
- const SkPoint* lines = flip ? insetLines : outsetLines;
- SkScalar minCoverage = 1.f;
- for (int i = 0; i < 4; ++i) {
- // Multiply by negative 1 so that outside points have negative distances
- SkScalar d = (flip ? 1 : -1) * signed_distance(point, lines[i * 2], lines[i * 2 + 1]);
- if (!edgeAA[i] && d >= -1e-4f) {
- d = 1.f;
- }
- if (d < minCoverage) {
- minCoverage = d;
- if (minCoverage < 0.f) {
- break; // Outside the shape
- }
- }
- }
- return minCoverage < 0.f ? 0.f : minCoverage;
- }
- static bool inside_triangle(const SkPoint& point, const SkPoint& t0, const SkPoint& t1,
- const SkPoint& t2, SkScalar bary[3]) {
- // Check sign of t0 to (t1,t2). If it is positive, that means the normals point into the
- // triangle otherwise the normals point outside the triangle so update edge distances as
- // necessary
- bool flip = signed_distance(t0, t1, t2) < 0.f;
- SkScalar d0 = (flip ? -1 : 1) * signed_distance(point, t0, t1);
- SkScalar d1 = (flip ? -1 : 1) * signed_distance(point, t1, t2);
- SkScalar d2 = (flip ? -1 : 1) * signed_distance(point, t2, t0);
- // Be a little forgiving
- if (d0 < -1e-4f || d1 < -1e-4f || d2 < -1e-4f) {
- return false;
- }
- // Inside, so calculate barycentric coords from the sideline distances
- SkScalar d01 = (t0 - t1).length();
- SkScalar d12 = (t1 - t2).length();
- SkScalar d20 = (t2 - t0).length();
- if (SkScalarNearlyZero(d12) || SkScalarNearlyZero(d20) || SkScalarNearlyZero(d01)) {
- // Empty degenerate triangle
- return false;
- }
- // Coordinates for a vertex use distances to the opposite edge
- bary[0] = d1 * d12;
- bary[1] = d2 * d20;
- bary[2] = d0 * d01;
- // And normalize
- SkScalar sum = bary[0] + bary[1] + bary[2];
- bary[0] /= sum;
- bary[1] /= sum;
- bary[2] /= sum;
- return true;
- }
- static SkScalar get_framed_coverage(const SkPoint outer[4], const SkScalar outerCoverages[4],
- const SkPoint inner[4], const SkScalar innerCoverages[4],
- const SkRect& geomDomain, const SkPoint& point) {
- // Triangles are ordered clock wise. Indices >= 4 refer to inner[i - 4]. Otherwise its outer[i].
- static const int kFrameTris[] = {
- 0, 1, 4, 4, 1, 5,
- 1, 2, 5, 5, 2, 6,
- 2, 3, 6, 6, 3, 7,
- 3, 0, 7, 7, 0, 4,
- 4, 5, 7, 7, 5, 6
- };
- static const int kNumTris = 10;
- SkScalar bary[3];
- for (int i = 0; i < kNumTris; ++i) {
- int i0 = kFrameTris[i * 3];
- int i1 = kFrameTris[i * 3 + 1];
- int i2 = kFrameTris[i * 3 + 2];
- SkPoint t0 = i0 >= 4 ? inner[i0 - 4] : outer[i0];
- SkPoint t1 = i1 >= 4 ? inner[i1 - 4] : outer[i1];
- SkPoint t2 = i2 >= 4 ? inner[i2 - 4] : outer[i2];
- if (inside_triangle(point, t0, t1, t2, bary)) {
- // Calculate coverage by barycentric interpolation of coverages
- SkScalar c0 = i0 >= 4 ? innerCoverages[i0 - 4] : outerCoverages[i0];
- SkScalar c1 = i1 >= 4 ? innerCoverages[i1 - 4] : outerCoverages[i1];
- SkScalar c2 = i2 >= 4 ? innerCoverages[i2 - 4] : outerCoverages[i2];
- SkScalar coverage = bary[0] * c0 + bary[1] * c1 + bary[2] * c2;
- if (coverage < 0.5f) {
- // Check distances to domain
- SkScalar l = SkScalarPin(point.fX - geomDomain.fLeft, 0.f, 1.f);
- SkScalar t = SkScalarPin(point.fY - geomDomain.fTop, 0.f, 1.f);
- SkScalar r = SkScalarPin(geomDomain.fRight - point.fX, 0.f, 1.f);
- SkScalar b = SkScalarPin(geomDomain.fBottom - point.fY, 0.f, 1.f);
- coverage = SkMinScalar(coverage, l * t * r * b);
- }
- return coverage;
- }
- }
- // Not inside any triangle
- return 0.f;
- }
- static constexpr SkScalar kViewScale = 100.f;
- static constexpr SkScalar kViewOffset = 200.f;
- class DegenerateQuadSample : public Sample {
- public:
- DegenerateQuadSample(const SkRect& rect)
- : fOuterRect(rect)
- , fCoverageMode(CoverageMode::kArea) {
- fOuterRect.toQuad(fCorners);
- for (int i = 0; i < 4; ++i) {
- fEdgeAA[i] = true;
- }
- }
- void onDrawContent(SkCanvas* canvas) override {
- static const SkScalar kDotParams[2] = {1.f / kViewScale, 12.f / kViewScale};
- sk_sp<SkPathEffect> dots = SkDashPathEffect::Make(kDotParams, 2, 0.f);
- static const SkScalar kDashParams[2] = {8.f / kViewScale, 12.f / kViewScale};
- sk_sp<SkPathEffect> dashes = SkDashPathEffect::Make(kDashParams, 2, 0.f);
- SkPaint circlePaint;
- circlePaint.setAntiAlias(true);
- SkPaint linePaint;
- linePaint.setAntiAlias(true);
- linePaint.setStyle(SkPaint::kStroke_Style);
- linePaint.setStrokeWidth(4.f / kViewScale);
- linePaint.setStrokeJoin(SkPaint::kRound_Join);
- linePaint.setStrokeCap(SkPaint::kRound_Cap);
- canvas->translate(kViewOffset, kViewOffset);
- canvas->scale(kViewScale, kViewScale);
- // Draw the outer rectangle as a dotted line
- linePaint.setPathEffect(dots);
- canvas->drawRect(fOuterRect, linePaint);
- bool valid = this->isValid();
- if (valid) {
- SkPoint outsets[8];
- SkPoint insets[8];
- // Calculate inset and outset lines for edge-distance visualization
- for (int i = 0; i < 4; ++i) {
- make_aa_line(fCorners[i], fCorners[(i + 1) % 4], fEdgeAA[i], true, outsets + i * 2);
- make_aa_line(fCorners[i], fCorners[(i + 1) % 4], fEdgeAA[i], false, insets + i * 2);
- }
- // Calculate inner and outer meshes for GPU visualization
- SkPoint gpuOutset[4];
- SkScalar gpuOutsetCoverage[4];
- SkPoint gpuInset[4];
- SkScalar gpuInsetCoverage[4];
- SkRect gpuDomain;
- this->getTessellatedPoints(gpuInset, gpuInsetCoverage, gpuOutset, gpuOutsetCoverage,
- &gpuDomain);
- // Visualize the coverage values across the clamping rectangle, but test pixels outside
- // of the "outer" rect since some quad edges can be outset extra far.
- SkPaint pixelPaint;
- pixelPaint.setAntiAlias(true);
- SkRect covRect = fOuterRect.makeOutset(2.f, 2.f);
- for (SkScalar py = covRect.fTop; py < covRect.fBottom; py += 1.f) {
- for (SkScalar px = covRect.fLeft; px < covRect.fRight; px += 1.f) {
- // px and py are the top-left corner of the current pixel, so get center's
- // coordinate
- SkPoint pixelCenter = {px + 0.5f, py + 0.5f};
- SkScalar coverage;
- if (fCoverageMode == CoverageMode::kArea) {
- coverage = get_area_coverage(fEdgeAA, fCorners, pixelCenter);
- } else if (fCoverageMode == CoverageMode::kEdgeDistance) {
- coverage = get_edge_dist_coverage(fEdgeAA, fCorners, outsets, insets,
- pixelCenter);
- } else {
- SkASSERT(fCoverageMode == CoverageMode::kGPUMesh);
- coverage = get_framed_coverage(gpuOutset, gpuOutsetCoverage,
- gpuInset, gpuInsetCoverage, gpuDomain,
- pixelCenter);
- }
- SkRect pixelRect = SkRect::MakeXYWH(px, py, 1.f, 1.f);
- pixelRect.inset(0.1f, 0.1f);
- SkScalar a = 1.f - 0.5f * coverage;
- pixelPaint.setColor4f({a, a, a, 1.f}, nullptr);
- canvas->drawRect(pixelRect, pixelPaint);
- pixelPaint.setColor(coverage > 0.f ? SK_ColorGREEN : SK_ColorRED);
- pixelRect.inset(0.38f, 0.38f);
- canvas->drawRect(pixelRect, pixelPaint);
- }
- }
- linePaint.setPathEffect(dashes);
- // Draw the inset/outset "infinite" lines
- if (fCoverageMode == CoverageMode::kEdgeDistance) {
- for (int i = 0; i < 4; ++i) {
- if (fEdgeAA[i]) {
- linePaint.setColor(SK_ColorBLUE);
- draw_extended_line(canvas, linePaint, outsets[i * 2], outsets[i * 2 + 1]);
- linePaint.setColor(SK_ColorGREEN);
- draw_extended_line(canvas, linePaint, insets[i * 2], insets[i * 2 + 1]);
- } else {
- // Both outset and inset are the same line, so only draw one in cyan
- linePaint.setColor(SK_ColorCYAN);
- draw_extended_line(canvas, linePaint, outsets[i * 2], outsets[i * 2 + 1]);
- }
- }
- }
- linePaint.setPathEffect(nullptr);
- // What is tessellated using GrQuadPerEdgeAA
- if (fCoverageMode == CoverageMode::kGPUMesh) {
- SkPath outsetPath;
- outsetPath.addPoly(gpuOutset, 4, true);
- linePaint.setColor(SK_ColorBLUE);
- canvas->drawPath(outsetPath, linePaint);
- SkPath insetPath;
- insetPath.addPoly(gpuInset, 4, true);
- linePaint.setColor(SK_ColorGREEN);
- canvas->drawPath(insetPath, linePaint);
- SkPaint domainPaint = linePaint;
- domainPaint.setStrokeWidth(2.f / kViewScale);
- domainPaint.setPathEffect(dashes);
- domainPaint.setColor(SK_ColorMAGENTA);
- canvas->drawRect(gpuDomain, domainPaint);
- }
- // Draw the edges of the true quad as a solid line
- SkPath path;
- path.addPoly(fCorners, 4, true);
- linePaint.setColor(SK_ColorBLACK);
- canvas->drawPath(path, linePaint);
- } else {
- // Draw the edges of the true quad as a solid *red* line
- SkPath path;
- path.addPoly(fCorners, 4, true);
- linePaint.setColor(SK_ColorRED);
- linePaint.setPathEffect(nullptr);
- canvas->drawPath(path, linePaint);
- }
- // Draw the four clickable corners as circles
- circlePaint.setColor(valid ? SK_ColorBLACK : SK_ColorRED);
- for (int i = 0; i < 4; ++i) {
- canvas->drawCircle(fCorners[i], 5.f / kViewScale, circlePaint);
- }
- }
- Sample::Click* onFindClickHandler(SkScalar x, SkScalar y, ModifierKey) override;
- bool onClick(Sample::Click*) override;
- bool onChar(SkUnichar) override;
- SkString name() override { return SkString("DegenerateQuad"); }
- private:
- class Click;
- enum class CoverageMode {
- kArea, kEdgeDistance, kGPUMesh
- };
- const SkRect fOuterRect;
- SkPoint fCorners[4]; // TL, TR, BR, BL
- bool fEdgeAA[4]; // T, R, B, L
- CoverageMode fCoverageMode;
- bool isValid() const {
- SkPath path;
- path.addPoly(fCorners, 4, true);
- return path.isConvex();
- }
- void getTessellatedPoints(SkPoint inset[4], SkScalar insetCoverage[4], SkPoint outset[4],
- SkScalar outsetCoverage[4], SkRect* domain) const {
- // Fixed vertex spec for extracting the picture frame geometry
- static const GrQuadPerEdgeAA::VertexSpec kSpec =
- {GrQuad::Type::kGeneral, GrQuadPerEdgeAA::ColorType::kNone,
- GrQuad::Type::kAxisAligned, false, GrQuadPerEdgeAA::Domain::kNo,
- GrAAType::kCoverage, false};
- static const GrQuad kIgnored(SkRect::MakeEmpty());
- GrQuadAAFlags flags = GrQuadAAFlags::kNone;
- flags |= fEdgeAA[0] ? GrQuadAAFlags::kTop : GrQuadAAFlags::kNone;
- flags |= fEdgeAA[1] ? GrQuadAAFlags::kRight : GrQuadAAFlags::kNone;
- flags |= fEdgeAA[2] ? GrQuadAAFlags::kBottom : GrQuadAAFlags::kNone;
- flags |= fEdgeAA[3] ? GrQuadAAFlags::kLeft : GrQuadAAFlags::kNone;
- GrQuad quad = GrQuad::MakeFromSkQuad(fCorners, SkMatrix::I());
- float vertices[56]; // 2 quads, with x, y, coverage, and geometry domain (7 floats x 8 vert)
- GrQuadPerEdgeAA::Tessellate(vertices, kSpec, quad, {1.f, 1.f, 1.f, 1.f},
- GrQuad(SkRect::MakeEmpty()), SkRect::MakeEmpty(), flags);
- // The first quad in vertices is the inset, then the outset, but they
- // are ordered TL, BL, TR, BR so un-interleave coverage and re-arrange
- inset[0] = {vertices[0], vertices[1]}; // TL
- insetCoverage[0] = vertices[2];
- inset[3] = {vertices[7], vertices[8]}; // BL
- insetCoverage[3] = vertices[9];
- inset[1] = {vertices[14], vertices[15]}; // TR
- insetCoverage[1] = vertices[16];
- inset[2] = {vertices[21], vertices[22]}; // BR
- insetCoverage[2] = vertices[23];
- outset[0] = {vertices[28], vertices[29]}; // TL
- outsetCoverage[0] = vertices[30];
- outset[3] = {vertices[35], vertices[36]}; // BL
- outsetCoverage[3] = vertices[37];
- outset[1] = {vertices[42], vertices[43]}; // TR
- outsetCoverage[1] = vertices[44];
- outset[2] = {vertices[49], vertices[50]}; // BR
- outsetCoverage[2] = vertices[51];
- *domain = {vertices[52], vertices[53], vertices[54], vertices[55]};
- }
- typedef Sample INHERITED;
- };
- class DegenerateQuadSample::Click : public Sample::Click {
- public:
- Click(const SkRect& clamp, int index)
- : fOuterRect(clamp)
- , fIndex(index) {}
- void doClick(SkPoint points[4]) {
- if (fIndex >= 0) {
- this->drag(&points[fIndex]);
- } else {
- for (int i = 0; i < 4; ++i) {
- this->drag(&points[i]);
- }
- }
- }
- private:
- SkRect fOuterRect;
- int fIndex;
- void drag(SkPoint* point) {
- SkPoint delta = fCurr - fPrev;
- *point += SkPoint::Make(delta.x() / kViewScale, delta.y() / kViewScale);
- point->fX = SkMinScalar(fOuterRect.fRight, SkMaxScalar(point->fX, fOuterRect.fLeft));
- point->fY = SkMinScalar(fOuterRect.fBottom, SkMaxScalar(point->fY, fOuterRect.fTop));
- }
- };
- Sample::Click* DegenerateQuadSample::onFindClickHandler(SkScalar x, SkScalar y, ModifierKey) {
- SkPoint inCTM = SkPoint::Make((x - kViewOffset) / kViewScale, (y - kViewOffset) / kViewScale);
- for (int i = 0; i < 4; ++i) {
- if ((fCorners[i] - inCTM).length() < 10.f / kViewScale) {
- return new Click(fOuterRect, i);
- }
- }
- return new Click(fOuterRect, -1);
- }
- bool DegenerateQuadSample::onClick(Sample::Click* click) {
- Click* myClick = (Click*) click;
- myClick->doClick(fCorners);
- return true;
- }
- bool DegenerateQuadSample::onChar(SkUnichar code) {
- switch(code) {
- case '1':
- fEdgeAA[0] = !fEdgeAA[0];
- return true;
- case '2':
- fEdgeAA[1] = !fEdgeAA[1];
- return true;
- case '3':
- fEdgeAA[2] = !fEdgeAA[2];
- return true;
- case '4':
- fEdgeAA[3] = !fEdgeAA[3];
- return true;
- case 'q':
- fCoverageMode = CoverageMode::kArea;
- return true;
- case 'w':
- fCoverageMode = CoverageMode::kEdgeDistance;
- return true;
- case 'e':
- fCoverageMode = CoverageMode::kGPUMesh;
- return true;
- }
- return false;
- }
- DEF_SAMPLE(return new DegenerateQuadSample(SkRect::MakeWH(4.f, 4.f));)
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