Prevent outset Ws from going negative
Bug: skia:9028 Change-Id: I8e3d37050d3fce7602eee62ae911eae756e603a2 Reviewed-on: https://skia-review.googlesource.com/c/skia/+/211100 Commit-Queue: Michael Ludwig <michaelludwig@google.com> Reviewed-by: Brian Osman <brianosman@google.com>
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Michael Ludwig
Skia Commit-Bot
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784184ab93
159
gm/postercircle.cpp
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159
gm/postercircle.cpp
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/*
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* Copyright 2019 Google Inc.
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*
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* Use of this source code is governed by a BSD-style license that can be
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* found in the LICENSE file.
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*/
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#include "gm/gm.h"
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#include "include/core/SkCanvas.h"
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#include "include/core/SkFont.h"
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#include "include/core/SkImage.h"
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#include "include/core/SkRRect.h"
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#include "include/core/SkSurface.h"
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#include "tools/timer/AnimTimer.h"
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// Mimics https://output.jsbin.com/falefice/1/quiet?CC_POSTER_CIRCLE, which can't be captured as
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// an SKP due to many 3D layers being composited post-SKP capture.
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// See skbug.com/9028
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class PosterCircleGM : public skiagm::GM {
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public:
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PosterCircleGM() : fTime(0.f) {}
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protected:
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SkString onShortName() override {
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return SkString("poster_circle");
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}
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SkISize onISize() override {
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return SkISize::Make(kStageWidth, kStageHeight + 50);
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}
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bool onAnimate(const AnimTimer& timer) override {
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#if 0
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if (timer.isRunning()) {
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// Use a fixed timestep
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fTime += 5e-4f;
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}
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#else
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fTime = timer.scaled(0.5f);
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#endif
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return true;
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}
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void onOnceBeforeDraw() override {
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SkFont font;
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font.setEdging(SkFont::Edging::kAntiAlias);
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font.setEmbolden(true);
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font.setSize(24.f);
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sk_sp<SkSurface> surface = SkSurface::MakeRasterN32Premul(kPosterSize, kPosterSize);
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for (int i = 0; i < kNumAngles; ++i) {
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SkCanvas* canvas = surface->getCanvas();
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SkPaint fillPaint;
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fillPaint.setAntiAlias(true);
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fillPaint.setColor(i % 2 == 0 ? SkColorSetRGB(0x99, 0x5C, 0x7F)
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: SkColorSetRGB(0x83, 0x5A, 0x99));
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canvas->drawRRect(SkRRect::MakeRectXY(SkRect::MakeWH(kPosterSize, kPosterSize),
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10.f, 10.f), fillPaint);
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SkString label;
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label.printf("%d", i);
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SkRect labelBounds;
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font.measureText(label.c_str(), label.size(), kUTF8_SkTextEncoding, &labelBounds);
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SkScalar labelX = 0.5f * kPosterSize - 0.5f * labelBounds.width();
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SkScalar labelY = 0.5f * kPosterSize + 0.5f * labelBounds.height();
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SkPaint labelPaint;
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labelPaint.setAntiAlias(true);
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canvas->drawString(label, labelX, labelY, font, labelPaint);
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fPosterImages[i] = surface->makeImageSnapshot();
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}
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}
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void onDraw(SkCanvas* canvas) override {
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// See https://developer.mozilla.org/en-US/docs/Web/CSS/transform-function/perspective
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// for projection matrix when --webkit-perspective: 800px is used.
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SkMatrix44 proj(SkMatrix44::kIdentity_Constructor);
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proj.set(3, 2, -1.f / 800.f);
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for (int pass = 0; pass < 2; ++pass) {
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// Want to draw 90 to 270 first (the back), then 270 to 90 (the front), but do all 3
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// rings backsides, then their frontsides since the front projections overlap across
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// rings. Note: we skip the poster circle's x axis rotation because that complicates the
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// back-to-front drawing order and it isn't necessary to trigger draws aligned with Z.
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bool drawFront = pass > 0;
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for (int y = 0; y < 3; ++y) {
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float ringY = (y - 1) * (kPosterSize + 10.f);
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for (int i = 0; i < kNumAngles; ++i) {
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// Add an extra 45 degree rotation, which triggers the bug by aligning some of
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// the posters with the z axis.
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SkScalar yDuration = 5.f - y;
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SkScalar yRotation = SkScalarMod(kAngleStep * i +
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360.f * SkScalarMod(fTime / yDuration, yDuration), 360.f);
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// These rotation limits were chosen manually to line up with current projection
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static constexpr SkScalar kBackMinAngle = 70.f;
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static constexpr SkScalar kBackMaxAngle = 290.f;
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if (drawFront) {
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if (yRotation >= kBackMinAngle && yRotation <= kBackMaxAngle) {
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// Back portion during a front draw
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continue;
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}
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} else {
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if (yRotation < kBackMinAngle || yRotation > kBackMaxAngle) {
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// Front portion during a back draw
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continue;
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}
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}
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canvas->save();
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// Matrix matches transform: rotateY(<angle>deg) translateZ(200px); nested in an
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// element with the perspective projection matrix above.
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SkMatrix44 model;
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// No post/preRotate, so start with rotation matrix and adjust from there
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model.setRotateAboutUnit(0.f, 1.f, 0.f, SkDegreesToRadians(yRotation));
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model.preTranslate(0.f, 0.f, kRingRadius); // *before* rotation
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model.postTranslate(0.f, ringY, 0.f); // *after* rotation
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model.postConcat(proj);
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model.postTranslate(0.5f * kStageWidth, 0.5f * kStageHeight + 25, 0.f);
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// Flatten the 4x4 matrix by discarding the 3rd row and column
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canvas->concat(SkMatrix::MakeAll(
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model.get(0, 0), model.get(0, 1), model.get(0, 3),
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model.get(1, 0), model.get(1, 1), model.get(1, 3),
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model.get(3, 0), model.get(3, 1), model.get(3, 3)));
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SkRect poster = SkRect::MakeLTRB(-0.5f * kPosterSize, -0.5f * kPosterSize,
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0.5f * kPosterSize, 0.5f * kPosterSize);
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SkPaint fillPaint;
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fillPaint.setAntiAlias(true);
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fillPaint.setAlphaf(0.7f);
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fillPaint.setFilterQuality(kLow_SkFilterQuality);
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canvas->drawImageRect(fPosterImages[i], poster, &fillPaint);
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canvas->restore();
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}
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}
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}
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}
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private:
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static const int kAngleStep = 30;
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static const int kNumAngles = 12; // 0 through 330 degrees
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static const int kStageWidth = 600;
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static const int kStageHeight = 400;
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static const int kRingRadius = 200;
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static const int kPosterSize = 100;
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sk_sp<SkImage> fPosterImages[kNumAngles];
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SkScalar fTime;
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};
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DEF_GM(return new PosterCircleGM();)
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@ -275,6 +275,7 @@ gm_sources = [
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"$_gm/poly2poly.cpp",
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"$_gm/polygons.cpp",
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"$_gm/polygonoffset.cpp",
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"$_gm/postercircle.cpp",
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"$_gm/quadpaths.cpp",
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"$_gm/radial_gradient_precision.cpp",
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"$_gm/readpixels.cpp",
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@ -258,6 +258,19 @@ static void outset_projected_vertices(const V4f& x2d, const V4f& y2d,
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V4f(0.f)) / denom; /* !B */
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}
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V4f newW = quad->fW + a * e1w + b * e2w;
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// If newW < 0, scale a and b such that the point reaches the infinity plane instead of crossing
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// This breaks orthogonality of inset/outsets, but GPUs don't handle negative Ws well so this
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// is far less visually disturbing (likely not noticeable since it's at extreme perspective).
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// The alternative correction (multiply xyw by -1) has the disadvantage of changing how local
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// coordinates would be interpolated.
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static const float kMinW = 1e-6f;
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if (any(newW < 0.f)) {
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V4f scale = if_then_else(newW < kMinW, (kMinW - quad->fW) / (newW - quad->fW), V4f(1.f));
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a *= scale;
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b *= scale;
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}
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quad->fX += a * e1x + b * e2x;
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quad->fY += a * e1y + b * e2y;
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quad->fW += a * e1w + b * e2w;
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