| /* |
| * 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, skui::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, skui::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));) |
