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Issue
1124423007:
Improve NVPR stroke accuracy to fix thick strokes (Closed)
DescriptionImprove NVPR stroke accuracy to fix thick strokes
Set the "path stroke error bound" path parameter to 0.02 for all paths.
This means that the stroked path area will be within 98% of the stroke
width in path space.
This should fix many cases where NVPR stroked paths were visibly different to
Skia stroked paths. One such path is in dashcubics gm.
This increases the amount of subdivisions the path object creation will
make for paths that need it. This in turn will increase gpu object space
requirements sligthly. Both of these effects should be unnoticeable.
GL_NV_path_rendering.txt:
"""
Every path object has a stroke approximation bound parameter
(PATH_STROKE_BOUND_NV) that is a floating-point value /sab/ clamped
between 0.0 and 1.0 and set and queried with the PATH_STROKE_BOUND_NV
path parameter. Exact determination of samples swept an orthogonal
centered line segment along cubic Bezier segments and rational
quadratic Bezier curves (so non-circular partial elliptical arcs) is
intractable for real-time rendering so an approximation is required;
/sab/ intuitively bounds the approximation error as a percentage of
the path object's stroke width. Specifically, this path parameter
requests the implementation to stencil any samples within /sweep/
object space units of the exact sweep of the path's cubic Bezier
segments or partial elliptical arcs to be sampled by the stroke where
sweep = ((1-sab)*sw)/2
where /sw/ is the path object's stroke width. The initial value
of /sab/ when a path is created is 0.2. In practical terms, this
initial value means the stencil sample positions coverage within 80%
(100%-20%) of the stroke width of cubic and rational quadratic stroke
segments should be sampled.
"""
BUG=skia:2049
Committed: https://skia.googlesource.com/skia/+/55e4783b5175fe43103c871ad8ad5cdcad208af4
Patch Set 1 #
Messages
Total messages: 6 (2 generated)
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