Rearranges the algebra to use "precision". This makes it consistent
with the other formulas and removes the need for the caller to think
about inverting its precision value.
Bug: skia:10419
Change-Id: I186d03393952983e86b0bef69e1f89f86cdbb423
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/414616
Commit-Queue: Chris Dalton <csmartdalton@google.com>
Reviewed-by: Tyler Denniston <tdenniston@google.com>
- most of the small diffs are because I moved GrWangsFormula.h out
of the tessellate/ directory and into the geometry/ directory since
it's more general than HW tessellation.
The previous implementation was based on the heuristic that the distance
from the true curve to the line segment would be divided by 4 every time
the curve was recursively subdivided. This was a reasonable
approximation if the curve had balanced curvature on both sides of the
split. However, in the case of the new GM's curve, the left half was
already very linear and the right half had much higher curves.
This lead to the approximation reporting fewer points than required.
Theoretically, those few points that weren't utilized by the left half
of the curve could have been made available to the right half, but the
implementation of that would be tricky.
Instead, it now uses Wang's formula to compute the number of points.
Since recursive subdivision leads to linearly spaced samples assuming it
can't stop early, this point count represents a valid upper bound on
what's needed. It also then ensures both left and right halves of a
curve have the point counts they might need w/o updating the
generation implementations. However, since the recursive point
generation exits once each section has reached the error tolerance, in
scenarios where the prior approximation was reasonable, we'll end up
using fewer points than reported by Wang's. Hopefully that means there
is negligible performance regression since we won't be increasing
vertex counts by that much (except where needed for correctness).
Bug: skia:11886
Change-Id: Iba39dbe4de82011775524583efd461b10c9259fe
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/405197
Reviewed-by: Chris Dalton <csmartdalton@google.com>
Reviewed-by: Brian Salomon <bsalomon@google.com>
Commit-Queue: Michael Ludwig <michaelludwig@google.com>
- Treat randomly generated control points as pre-projected
- Use double-precision conic evaluation for "within tolerance" test.
This allows us to test with larger magnitude control points (the
SkConic/SkGeometry single-precision functions lose too much accuracy).
Bug: skia:10419
Change-Id: Iba0915dccb50131e1a1b28a7d556863497f636e9
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/367057
Commit-Queue: Tyler Denniston <tdenniston@google.com>
Reviewed-by: Chris Dalton <csmartdalton@google.com>
Also add a unit test that the vectorized version equals the reference
implementation.
Bug: skia:10419
Change-Id: I4d165fd45532e9ec468565d0637fb769b51f5fcd
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/345122
Commit-Queue: Tyler Denniston <tdenniston@google.com>
Reviewed-by: Chris Dalton <csmartdalton@google.com>
Initial data suggests that the non-rational Wang's formula does not
form an upper bound for the rational case, so additional work is needed
to handle them. Note this new formula is not actually due to Wang,
but is an analogue.
The version added in this CL is for cubic rationals because the current
tessellation code promotes all curve segments to cubic rationals for
ease. If we end up using this approach, it would be likely simpler and
faster to implement the degree-2 version and handle conics separately
during tessellation.
From:
J. Zheng, T. Sederberg. "Estimating Tessellation Parameter Intervals for
Rational Curves and Surfaces." ACM Transactions on Graphics 19(1). 2000.
Bug: skia:10419
Change-Id: Ie02e229c089541ece05c7502217b1ef5d4799b52
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/337720
Commit-Queue: Tyler Denniston <tdenniston@google.com>
Reviewed-by: Chris Dalton <csmartdalton@google.com>
Just verify that the max error on any of the intervals after splitting
is less than the specified tolerance. Looks like we're running into
some FP precision issues with large coord values, so I'm limiting the
max multiplier to 2^15 in this test.
Bug: skia:10419
Change-Id: I39e76dca5f77389833ba3c94930e6b67c2b1bc97
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/340116
Reviewed-by: Chris Dalton <csmartdalton@google.com>
Commit-Queue: Tyler Denniston <tdenniston@google.com>
We finally have a reference and derivation of Wang's formula, thanks to
tdenniston@. And it turns out that the formula we had been using for
cubics wasn't quite right. It was overly conservative for certain types
of curves.
This CL fixes the incorrect cubic formulas and adds a citation to the
"Pyramid Algorithms" book. We should now be getting by with fewer linear
segments.
Bug: skia:10419
Change-Id: Ib850c7b4d17b8d9f9abed800cc7cb5f074df6e17
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/331156
Reviewed-by: Tyler Denniston <tdenniston@google.com>
Commit-Queue: Chris Dalton <csmartdalton@google.com>
Bug: skia:10419
Change-Id: I1544113b6ea2327674a48a0430146a859a547723
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/322796
Commit-Queue: Chris Dalton <csmartdalton@google.com>
Reviewed-by: Michael Ludwig <michaelludwig@google.com>
Adds various optimizations to GrWangsFormula as well as "pow4" variants
of the formula that are quicker than the standard and/or log2 versions.
Uses the pow4 variants in GrStrokePatchBuilder.
Bug: skia:10419
Change-Id: I8478582df5296b088d25808bcaeb93107ff20797
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/318954
Reviewed-by: Michael Ludwig <michaelludwig@google.com>
Commit-Queue: Chris Dalton <csmartdalton@google.com>
Other code outside this namespace will want to use this method soon.
Bug: skia:10419
Change-Id: Ib155f224866fd333b8f9a4b78e6c9e51ac0600df
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/311936
Commit-Queue: Chris Dalton <csmartdalton@google.com>
Reviewed-by: Brian Salomon <bsalomon@google.com>
Adds a method to determine the worst-case number of tessellated line
segments that a path might require, and disables hardware tessellation
if it is more segments than are supported (falling back on indirect
draw shaders).
If the path requires even more segments than are supported by the
indirect draw shaders (1024), we crop the path to the viewport. The
required number of segments is proportional to the square root of the
bounding box's diagonal, so we won't start cropping paths until their
device-space bounding box diagonal is nearly 175,000 pixels long.
Change-Id: I8a9435e70bb93dda3464cc11a3e44fbe511744ae
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/293691
Reviewed-by: Greg Daniel <egdaniel@google.com>
Reviewed-by: Brian Salomon <bsalomon@google.com>
Commit-Queue: Chris Dalton <csmartdalton@google.com>
This is a reland of e278e1c1c7
Original change's description:
> Add an implementation and log2 variants for Wang's formula
>
> Wang's formulas for cubics and quadratics (1985) tell us how many line
> segments a curve must be chopped into when tessellating. This CL adds
> an implementation along with optimized log2 variants, as well as tests
> and a benchmark.
>
> Change-Id: I3f777b8d0312c57c3a1cc24307de5945c70be287
> Reviewed-on: https://skia-review.googlesource.com/c/skia/+/288321
> Reviewed-by: Brian Salomon <bsalomon@google.com>
> Commit-Queue: Chris Dalton <csmartdalton@google.com>
TBR=bsalomon@google.com
Change-Id: Ie3822c62439fc579a59ea8adb49583224de41aa5
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/289680
Reviewed-by: Chris Dalton <csmartdalton@google.com>
Commit-Queue: Chris Dalton <csmartdalton@google.com>
This reverts commit e278e1c1c7.
Reason for revert: i think we need to do that add with an unsigned, or test instead of always += (1<<23)-1.
Original change's description:
> Add an implementation and log2 variants for Wang's formula
>
> Wang's formulas for cubics and quadratics (1985) tell us how many line
> segments a curve must be chopped into when tessellating. This CL adds
> an implementation along with optimized log2 variants, as well as tests
> and a benchmark.
>
> Change-Id: I3f777b8d0312c57c3a1cc24307de5945c70be287
> Reviewed-on: https://skia-review.googlesource.com/c/skia/+/288321
> Reviewed-by: Brian Salomon <bsalomon@google.com>
> Commit-Queue: Chris Dalton <csmartdalton@google.com>
TBR=bsalomon@google.com,brianosman@google.com,csmartdalton@google.com
Change-Id: I24dfd8549054b632f38f7b05b4d857b640cf5cd1
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/289658
Reviewed-by: Mike Klein <mtklein@google.com>
Commit-Queue: Mike Klein <mtklein@google.com>
Wang's formulas for cubics and quadratics (1985) tell us how many line
segments a curve must be chopped into when tessellating. This CL adds
an implementation along with optimized log2 variants, as well as tests
and a benchmark.
Change-Id: I3f777b8d0312c57c3a1cc24307de5945c70be287
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/288321
Reviewed-by: Brian Salomon <bsalomon@google.com>
Commit-Queue: Chris Dalton <csmartdalton@google.com>
