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author | commit-bot@chromium.org <commit-bot@chromium.org@2bbb7eff-a529-9590-31e7-b0007b416f81> | 2013-12-04 21:33:08 +0000 |
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committer | commit-bot@chromium.org <commit-bot@chromium.org@2bbb7eff-a529-9590-31e7-b0007b416f81> | 2013-12-04 21:33:08 +0000 |
commit | f543fd9e8c162b65fd04d1d9439b60911f8eb4c0 (patch) | |
tree | e76205b585fdd2a767e7a4eb0454c9511c984f93 /src/gpu/GrPathUtils.cpp | |
parent | c53f15c3bcc3e3f79ecdb3af8c8134a33d0b1c11 (diff) |
Simplify matrix generation for convex path renderer
Addresses precision issues which were leading to asserts in Debug
R=bsalomon@google.com, mtklein@google.com
Author: jvanverth@google.com
Review URL: https://codereview.chromium.org/102683002
git-svn-id: http://skia.googlecode.com/svn/trunk@12494 2bbb7eff-a529-9590-31e7-b0007b416f81
Diffstat (limited to 'src/gpu/GrPathUtils.cpp')
-rw-r--r-- | src/gpu/GrPathUtils.cpp | 59 |
1 files changed, 45 insertions, 14 deletions
diff --git a/src/gpu/GrPathUtils.cpp b/src/gpu/GrPathUtils.cpp index 81348ec239..824360285d 100644 --- a/src/gpu/GrPathUtils.cpp +++ b/src/gpu/GrPathUtils.cpp @@ -187,8 +187,6 @@ int GrPathUtils::worstCasePointCount(const SkPath& path, int* subpaths, } void GrPathUtils::QuadUVMatrix::set(const GrPoint qPts[3]) { - // can't make this static, no cons :( - SkMatrix UVpts; #ifndef SK_SCALAR_IS_FLOAT GrCrash("Expected scalar is float."); #endif @@ -197,18 +195,23 @@ void GrPathUtils::QuadUVMatrix::set(const GrPoint qPts[3]) { // We know M * control_pts = [0 1/2 1] // [0 0 1] // [1 1 1] + // And control_pts = [x0 x1 x2] + // [y0 y1 y2] + // [1 1 1 ] // We invert the control pt matrix and post concat to both sides to get M. - UVpts.setAll(0, SK_ScalarHalf, SK_Scalar1, - 0, 0, SK_Scalar1, - SkScalarToPersp(SK_Scalar1), - SkScalarToPersp(SK_Scalar1), - SkScalarToPersp(SK_Scalar1)); - m.setAll(qPts[0].fX, qPts[1].fX, qPts[2].fX, - qPts[0].fY, qPts[1].fY, qPts[2].fY, - SkScalarToPersp(SK_Scalar1), - SkScalarToPersp(SK_Scalar1), - SkScalarToPersp(SK_Scalar1)); - if (!m.invert(&m)) { + // Using the known form of the control point matrix and the result, we can + // optimize and improve precision. + + double x0 = qPts[0].fX; + double y0 = qPts[0].fY; + double x1 = qPts[1].fX; + double y1 = qPts[1].fY; + double x2 = qPts[2].fX; + double y2 = qPts[2].fY; + double det = x0*y1 - y0*x1 + x2*y0 - y2*x0 + x1*y2 - y1*x2; + + if (!sk_float_isfinite(det) + || SkScalarNearlyZero((float)det, SK_ScalarNearlyZero * SK_ScalarNearlyZero)) { // The quad is degenerate. Hopefully this is rare. Find the pts that are // farthest apart to compute a line (unless it is really a pt). SkScalar maxD = qPts[0].distanceToSqd(qPts[1]); @@ -247,7 +250,35 @@ void GrPathUtils::QuadUVMatrix::set(const GrPoint qPts[3]) { fM[3] = 0; fM[4] = 0; fM[5] = 100.f; } } else { - m.postConcat(UVpts); + double scale = 1.0/det; + + // compute adjugate matrix + double a0, a1, a2, a3, a4, a5, a6, a7, a8; + a0 = y1-y2; + a1 = x2-x1; + a2 = x1*y2-x2*y1; + + a3 = y2-y0; + a4 = x0-x2; + a5 = x2*y0-x0*y2; + + a6 = y0-y1; + a7 = x1-x0; + a8 = x0*y1-x1*y0; + + // this performs the uv_pts*adjugate(control_pts) multiply, + // then does the scale by 1/det afterwards to improve precision + m[SkMatrix::kMScaleX] = (float)((0.5*a3 + a6)*scale); + m[SkMatrix::kMSkewX] = (float)((0.5*a4 + a7)*scale); + m[SkMatrix::kMTransX] = (float)((0.5*a5 + a8)*scale); + + m[SkMatrix::kMSkewY] = (float)(a6*scale); + m[SkMatrix::kMScaleY] = (float)(a7*scale); + m[SkMatrix::kMTransY] = (float)(a8*scale); + + m[SkMatrix::kMPersp0] = (float)((a0 + a3 + a6)*scale); + m[SkMatrix::kMPersp1] = (float)((a1 + a4 + a7)*scale); + m[SkMatrix::kMPersp2] = (float)((a2 + a5 + a8)*scale); // The matrix should not have perspective. SkDEBUGCODE(static const SkScalar gTOL = 1.f / 100.f); |