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some cleanups for halfplanes

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Plan is to next move the clipper into utils / SkCanvas itself

Change-Id: Ia79c5bc2750a3a2719f901d255890a8c43ef1b42
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/257916
Reviewed-by: Mike Reed <reed@google.com>
Commit-Queue: Mike Reed <reed@google.com>
This commit is contained in:
Mike Reed 2019-12-04 12:45:39 -05:00 committed by Skia Commit-Bot
parent 67c0dcd894
commit 6344c29379
1 changed files with 95 additions and 85 deletions
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180
samplecode/SampleClip.cpp
View File

@ -141,9 +141,10 @@ DEF_SAMPLE( return new ClipView(); )
struct SkHalfPlane {
SkScalar fA, fB, fC;
SkScalar operator()(SkScalar x, SkScalar y) const {
SkScalar eval(SkScalar x, SkScalar y) const {
return fA * x + fB * y + fC;
}
SkScalar operator()(SkScalar x, SkScalar y) const { return this->eval(x, y); }
bool twoPts(SkPoint pts[2]) const {
// normalize plane to help with the perpendicular step, below
@ -172,11 +173,45 @@ struct SkHalfPlane {
SkASSERT(SkScalarNearlyZero(this->operator()(pts[1].fX, pts[1].fY)));
return true;
}
enum Result {
kAllNegative,
kAllPositive,
kMixed
};
Result test(const SkRect& bounds) const {
SkPoint diagMin, diagMax;
if (fA >= 0) {
diagMin.fX = bounds.fLeft;
diagMax.fX = bounds.fRight;
} else {
diagMin.fX = bounds.fRight;
diagMax.fX = bounds.fLeft;
}
if (fB >= 0) {
diagMin.fY = bounds.fTop;
diagMax.fY = bounds.fBottom;
} else {
diagMin.fY = bounds.fBottom;
diagMax.fY = bounds.fTop;
}
SkScalar test = this->eval(diagMin.fX, diagMin.fY);
SkScalar sign = test*this->eval(diagMax.fX, diagMin.fY);
if (sign > 0) {
// the path is either all on one side of the half-plane or the other
if (test < 0) {
return kAllNegative;
} else {
return kAllPositive;
}
}
return kMixed;
}
};
#include "src/core/SkEdgeClipper.h"
static SkPath clip(const SkPath& path, SkPoint p0, SkPoint p1) {
static void clip(const SkPath& path, SkPoint p0, SkPoint p1, SkPath* clippedPath) {
SkMatrix mx, inv;
SkVector v = p1 - p0;
mx.setAll(v.fX, -v.fY, p0.fX,
@ -191,9 +226,9 @@ static SkPath clip(const SkPath& path, SkPoint p0, SkPoint p1) {
SkRect clip = {-big, 0, big, big };
struct Rec {
SkPath fResult;
SkPath* fResult;
SkPoint fPrev;
} rec;
} rec = { clippedPath, {0, 0} };
SkEdgeClipper::ClipPath(rotated, clip, false,
[](SkEdgeClipper* clipper, bool newCtr, void* ctx) {
@ -204,26 +239,26 @@ static SkPath clip(const SkPath& path, SkPoint p0, SkPoint p1) {
SkPath::Verb verb;
while ((verb = clipper->next(pts)) != SkPath::kDone_Verb) {
if (newCtr) {
rec->fResult.moveTo(pts[0]);
rec->fResult->moveTo(pts[0]);
rec->fPrev = pts[0];
newCtr = false;
}
if (addLineTo || pts[0] != rec->fPrev) {
rec->fResult.lineTo(pts[0]);
rec->fResult->lineTo(pts[0]);
}
switch (verb) {
case SkPath::kLine_Verb:
rec->fResult.lineTo (pts[1]);
rec->fResult->lineTo(pts[1]);
rec->fPrev = pts[1];
break;
case SkPath::kQuad_Verb:
rec->fResult.quadTo(pts[1], pts[2]);
rec->fResult->quadTo(pts[1], pts[2]);
rec->fPrev = pts[2];
break;
case SkPath::kCubic_Verb:
rec->fResult.cubicTo(pts[1], pts[2], pts[3]);
rec->fResult->cubicTo(pts[1], pts[2], pts[3]);
rec->fPrev = pts[3];
break;
default: break;
@ -232,50 +267,27 @@ static SkPath clip(const SkPath& path, SkPoint p0, SkPoint p1) {
}
}, &rec);
rec.fResult.transform(mx);
return rec.fResult;
rec.fResult->transform(mx);
}
static SkPath clip(const SkPath& path, const SkHalfPlane& plane) {
// do a quick bounds check to see if we need to clip at all
const SkRect& bounds = path.getBounds();
// check whether the diagonal aligned with the normal crosses the plane
SkPoint diagMin, diagMax;
if (plane.fA >= 0) {
diagMin.fX = bounds.fLeft;
diagMax.fX = bounds.fRight;
} else {
diagMin.fX = bounds.fRight;
diagMax.fX = bounds.fLeft;
}
if (plane.fB >= 0) {
diagMin.fY = bounds.fTop;
diagMax.fY = bounds.fBottom;
} else {
diagMin.fY = bounds.fBottom;
diagMax.fY = bounds.fTop;
}
SkScalar test = plane(diagMin.fX, diagMin.fY);
SkScalar sign = test*plane(diagMax.fX, diagMin.fY);
if (sign > 0) {
// the path is either all on one side of the half-plane or the other
if (test < 0) {
// completely culled
return SkPath();
} else {
// no clipping necessary
return path;
}
}
// quick check failed, we have to clip
SkPoint pts[2];
if (plane.twoPts(pts)) {
return clip(path, pts[0], pts[1]);
} else {
return SkPath();
// true means use clippedPath.
// false means there was no clipping -- use the original path
static bool clip(const SkPath& path, const SkHalfPlane& plane, SkPath* clippedPath) {
switch (plane.test(path.getBounds())) {
case SkHalfPlane::kAllPositive:
return false;
case SkHalfPlane::kMixed: {
SkPoint pts[2];
if (plane.twoPts(pts)) {
clip(path, pts[0], pts[1], clippedPath);
return true;
}
} break;
default: break; // handled outside of the switch
}
// clipped out (or failed)
clippedPath->reset();
return true;
}
static void draw_halfplane(SkCanvas* canvas, SkPoint p0, SkPoint p1, SkColor c) {
@ -319,7 +331,10 @@ class HalfPlaneView : public Sample {
canvas->drawPath(fPath, paint);
paint.setColor({0, 0, 0, 1}, nullptr);
canvas->drawPath(clip(fPath, fPts[0], fPts[1]), paint);
SkPath clippedPath;
clip(fPath, fPts[0], fPts[1], &clippedPath);
canvas->drawPath(clippedPath, paint);
draw_halfplane(canvas, fPts[0], fPts[1], SK_ColorRED);
}
@ -430,6 +445,7 @@ static SkMatrix44 inv(const SkMatrix44& m) {
return inverse;
}
#if 0 // Jim's general half-planes math
static void half_planes(const SkMatrix44& m44, SkScalar W, SkScalar H, SkHalfPlane planes[6]) {
float mx[16];
m44.asColMajorf(mx);
@ -450,18 +466,10 @@ static void half_planes(const SkMatrix44& m44, SkScalar W, SkScalar H, SkHalfPla
planes[4] = { m - i, n - j, p - l }; // w - z
planes[5] = { m + i, n + j, p + l }; // w + z
}
#endif
static SkHalfPlane half_plane_w0(const SkMatrix44& m44, SkScalar W, SkScalar H) {
float mx[16];
m44.asColMajorf(mx);
SkScalar
// a = mx[0], b = mx[4], /* c = mx[ 8], */ d = mx[12],
// e = mx[1], f = mx[5], /* g = mx[ 9], */ h = mx[13],
// i = mx[2], j = mx[6], /* k = mx[10], */ l = mx[14],
m = mx[3], n = mx[7], /* o = mx[11], */ p = mx[15];
return { m, n, p - 0.05f }; // w = 0.05f
static SkHalfPlane half_plane_w0(const SkMatrix& m) {
return { m[SkMatrix::kMPersp0], m[SkMatrix::kMPersp1], m[SkMatrix::kMPersp2] - 0.05f };
}
class HalfPlaneView3 : public Sample {
@ -478,6 +486,7 @@ class HalfPlaneView3 : public Sample {
SkPath fPath;
sk_sp<SkShader> fShader;
bool fShowUnclipped = false;
SkString name() override { return SkString("halfplane3"); }
@ -514,8 +523,7 @@ class HalfPlaneView3 : public Sample {
}
void onDrawContent(SkCanvas* canvas) override {
SkMatrix44 mx44 = this->get44();
SkMatrix mx = mx44;
SkMatrix mx = this->get44();
SkPaint paint;
paint.setColor({0.75, 0.75, 0.75, 1});
@ -523,29 +531,29 @@ class HalfPlaneView3 : public Sample {
paint.setShader(fShader);
if (fShowUnclipped) {
canvas->save();
canvas->concat(mx);
paint.setAlphaf(0.33f);
canvas->drawPath(fPath, paint);
paint.setAlphaf(1.f);
canvas->restore();
}
SkHalfPlane hpw = half_plane_w0(mx);
SkColor planeColor = SK_ColorBLUE;
SkPath clippedPath, *path = &fPath;
if (clip(fPath, hpw, &clippedPath)) {
path = &clippedPath;
planeColor = SK_ColorRED;
}
canvas->save();
canvas->concat(mx);
paint.setAlphaf(0.33f);
canvas->drawPath(fPath, paint);
paint.setAlphaf(1.f);
canvas->drawPath(*path, paint);
canvas->restore();
SkHalfPlane planes[6];
half_planes(mx44, 400, 400, planes);
SkHalfPlane hpw = half_plane_w0(mx44, 400, 400);
SkPath path = clip(fPath, hpw);//planes[4]);
canvas->save();
canvas->concat(mx);
canvas->drawPath(path, paint);
canvas->restore();
// for (auto& p : planes) {
// draw_halfplane(canvas, p, SK_ColorRED);
// }
draw_halfplane(canvas, planes[4], SK_ColorBLUE);
// draw_halfplane(canvas, planes[5], SK_ColorGREEN);
draw_halfplane(canvas, hpw, SK_ColorRED);
draw_halfplane(canvas, hpw, planeColor);
}
bool onChar(SkUnichar uni) override {
@ -558,13 +566,15 @@ class HalfPlaneView3 : public Sample {
case '-': this->rotate(0, 0, delta); return true;
case '+': this->rotate(0, 0, -delta); return true;
case 'i': fTrans.fZ += 0.1f; SkDebugf("ez %g\n", fTrans.fZ); return true;
case 'k': fTrans.fZ -= 0.1f; SkDebugf("ez %g\n", fTrans.fZ); return true;
case 'i': fTrans.fZ += 0.1f; SkDebugf("z %g\n", fTrans.fZ); return true;
case 'k': fTrans.fZ -= 0.1f; SkDebugf("z %g\n", fTrans.fZ); return true;
case 'n': fNear += 0.1f; SkDebugf("near %g\n", fNear); return true;
case 'N': fNear -= 0.1f; SkDebugf("near %g\n", fNear); return true;
case 'f': fFar += 0.1f; SkDebugf("far %g\n", fFar); return true;
case 'F': fFar -= 0.1f; SkDebugf("far %g\n", fFar); return true;
case 'u': fShowUnclipped = !fShowUnclipped; return true;
default: break;
}
return false;