SkDPoint SkDConic::ptAtT(double t) const { if (t == 0) { return fPts[0]; } if (t == 1) { return fPts[2]; } double denominator = conic_eval_denominator(fWeight, t); SkDPoint result = { conic_eval_numerator(&fPts[0].fX, fWeight, t) / denominator, conic_eval_numerator(&fPts[0].fY, fWeight, t) / denominator }; return result; }
/* see quad subdivide for rationale */ SkDConic SkDConic::subDivide(double t1, double t2) const { double ax, ay, az; if (t1 == 0) { ax = fPts[0].fX; ay = fPts[0].fY; az = 1; } else if (t1 != 1) { ax = conic_eval_numerator(&fPts[0].fX, fWeight, t1); ay = conic_eval_numerator(&fPts[0].fY, fWeight, t1); az = conic_eval_denominator(fWeight, t1); } else { ax = fPts[2].fX; ay = fPts[2].fY; az = 1; } double midT = (t1 + t2) / 2; double dx = conic_eval_numerator(&fPts[0].fX, fWeight, midT); double dy = conic_eval_numerator(&fPts[0].fY, fWeight, midT); double dz = conic_eval_denominator(fWeight, midT); double cx, cy, cz; if (t2 == 1) { cx = fPts[2].fX; cy = fPts[2].fY; cz = 1; } else if (t2 != 0) { cx = conic_eval_numerator(&fPts[0].fX, fWeight, t2); cy = conic_eval_numerator(&fPts[0].fY, fWeight, t2); cz = conic_eval_denominator(fWeight, t2); } else { cx = fPts[0].fX; cy = fPts[0].fY; cz = 1; } double bx = 2 * dx - (ax + cx) / 2; double by = 2 * dy - (ay + cy) / 2; double bz = 2 * dz - (az + cz) / 2; double dt = t2 - t1; double dt_1 = 1 - dt; SkScalar w = SkDoubleToScalar((1 + dt * (fWeight - 1)) / sqrt(dt * dt + 2 * dt * dt_1 * fWeight + dt_1 * dt_1)); SkDConic dst = {{{{ax / az, ay / az}, {bx / bz, by / bz}, {cx / cz, cy / cz}}}, w }; return dst; }