diff --git a/crates/project/src/props.rs b/crates/project/src/props.rs index 6212a4b59..be2468c37 100644 --- a/crates/project/src/props.rs +++ b/crates/project/src/props.rs @@ -205,7 +205,8 @@ pub enum MaskMotionBlur { Off, } -/// How a mask's feather ramps: Smooth (Gaussian) or Linear. +/// How a mask's feather ramps: Smooth (three box passes, an S-shaped ramp of finite reach, as +/// measured in After Effects) or Linear (one box pass: a straight ramp). #[derive(Clone, Copy, Debug, Default, PartialEq, Eq, Hash, Serialize, Deserialize)] pub enum FeatherFalloff { #[default] diff --git a/crates/render/src/masks.rs b/crates/render/src/masks.rs index 04a6e63e9..f0e0eeee0 100644 --- a/crates/render/src/masks.rs +++ b/crates/render/src/masks.rs @@ -5,7 +5,7 @@ use effectcraft_geom::{Mat3, vec2}; use effectcraft_keyframe::Value; use effectcraft_path::{FillRule, Join}; use effectcraft_project::{FeatherFalloff, GroupKind, Layer, MaskMode, MaskMotionBlur}; -use effectcraft_raster::{Mask, box_blur, gaussian_blur}; +use effectcraft_raster::{Mask, box_blur}; use rayon::prelude::*; use crate::eval::EvalCtx; @@ -62,12 +62,20 @@ fn coverage(ctx: &EvalCtx, layer: &Layer, g: &effectcraft_project::PropGroup, bu /// The largest feather taken, in buffer pixels (larger and non-finite values are clamped). const MAX_FEATHER_PX: f64 = 1.0e6; -/// Up to this Gaussian sigma (box radius for a linear falloff: twice it) a feather is blurred at -/// the buffer's resolution. A wider one is blurred on a grid coarser per axis by the factor that -/// leaves it about `COARSE_SIGMA` grid pixels (2x for the box radius): a wide blur is smooth, so -/// the coarse grid loses nothing visible, and the padding stays about 50 grid pixels. -const FULL_RES_SIGMA: f64 = 32.0; -const COARSE_SIGMA: f64 = 16.0; +/// Smooth falloff (After Effects' default), measured on After Effects 2026 renders (feather 100, +/// 300 and 1000; red value along rows, columns and the corner diagonal of a feathered rect mask): +/// the edge is blurred separably by three box passes, each `2r + 1` pixels wide with +/// `r = round(SMOOTH_BOX_RADIUS * feather)`. That is a quadratic B-spline reaching about +/// 1.11 x feather either side of the path (finite support; a Gaussian of any width misses the +/// measured profile by 3/255 or more, this kernel by less than 1/255). +const SMOOTH_BOX_RADIUS: f64 = 0.37; +/// Up to this box radius (buffer pixels) a feather is blurred at the buffer's resolution. A wider +/// one is blurred on a grid coarser per axis, about `COARSE_RADIUS` grid pixels per box: a wide +/// blur is smooth, so the coarse grid loses nothing visible, and the padding stays about +/// 3 x `COARSE_RADIUS` grid pixels. (Box passes cost the same at any radius; the coarse grid +/// bounds the padded area, i.e. memory.) +const FULL_RES_RADIUS: usize = 48; +const COARSE_RADIUS: usize = 32; /// The largest padded grid (pixels); a bigger one (only reachable with a huge buffer) falls back /// to blurring within the buffer. const MAX_GRID_PX: usize = 1 << 26; @@ -75,13 +83,13 @@ const MAX_GRID_PX: usize = 1 << 26; const MAX_VARIABLE_PAD: usize = 256; /// One axis of the grid a feathered mask is rasterised and blurred on: `step` buffer pixels per -/// grid pixel, `pad` grid pixels on each side of the buffer, and the blur in grid pixels. +/// grid pixel, `pad` grid pixels on each side of the buffer, and the box radii in grid pixels. #[derive(Clone, Copy, Debug, PartialEq)] struct Axis { step: usize, pad: usize, - /// Gaussian sigma, or the box radius of a linear falloff. - blur: f64, + /// Radii of the box passes (Smooth: three; Linear: one, the others 0). + radii: [usize; 3], } impl Axis { @@ -89,24 +97,43 @@ impl Axis { /// the path outside the buffer reaches into it as on an unbounded plane. fn new(feather: f64, linear: bool, full_res_only: bool) -> Axis { let f = if feather.is_finite() { feather.clamp(0.0, MAX_FEATHER_PX) } else { 0.0 }; + let none = Axis { step: 1, pad: 0, radii: [0; 3] }; if f <= 0.0 { - return Axis { step: 1, pad: 0, blur: 0.0 }; + return none; } + let cap = |pad: usize| if full_res_only { pad.min(MAX_VARIABLE_PAD) } else { pad }; if linear { - // One box pass: a straight ramp `feather` pixels wide across the edge. - let r = (f / 2.0).round().max(1.0); - let step = if full_res_only || r <= 2.0 * FULL_RES_SIGMA { 1 } else { (r / (2.0 * COARSE_SIGMA)).ceil() as usize }; - let rg = (r / step as f64).round().max(1.0); - let pad = rg as usize; - Axis { step, pad: if full_res_only { pad.min(MAX_VARIABLE_PAD) } else { pad }, blur: rg } - } else { - let sigma = f / 2.0; - let step = if full_res_only || sigma <= FULL_RES_SIGMA { 1 } else { (sigma / COARSE_SIGMA).ceil() as usize }; - let sg = sigma / step as f64; - // Three box passes of radii summing to at most 1.5 * (sqrt(4 sigma^2 + 1) + 1) <= 3 sigma + 3. - let pad = (3.0 * sg).ceil() as usize + 3; - Axis { step, pad: if full_res_only { pad.min(MAX_VARIABLE_PAD) } else { pad }, blur: sg } + // Linear falloff (not measured against After Effects; kept as it was): one box pass, + // a straight ramp `feather` pixels wide across the edge. + let r = (f / 2.0).round().max(1.0) as usize; + let step = if full_res_only || r <= 2 * FULL_RES_RADIUS { 1 } else { r.div_ceil(2 * COARSE_RADIUS) }; + let rg = ((r as f64 / step as f64).round() as usize).max(1); + return Axis { step, pad: cap(rg), radii: [rg, 0, 0] }; } + let r = (SMOOTH_BOX_RADIUS * f).round() as usize; + if r == 0 { + return none; + } + if full_res_only || r <= FULL_RES_RADIUS { + return Axis { step: 1, pad: cap(3 * r + 1), radii: [r; 3] }; + } + // On a coarse grid the three windows (2 rg + 1 grid pixels each) should still add up to + // 3 (2r + 1) buffer pixels: of a few steps take the one that comes closest, and spread + // the radii over the passes. + let want = 3 * (2 * r + 1); + let s0 = r.div_ceil(COARSE_RADIUS); + let fit = |s: usize| -> (usize, usize) { + let sum = ((want as f64 / s as f64 - 3.0) / 2.0).round().max(0.0) as usize; + let got = (2 * sum + 3).saturating_mul(s); + (sum, got.abs_diff(want)) + }; + let (step, sum) = (s0..=s0 + (s0 / 2).min(8)).map(|s| (s, fit(s))).min_by_key(|&(s, (_, e))| (e, s)).map_or((s0, fit(s0).0), |(s, (sum, _))| (s, sum)); + let radii = [0, 1, 2].map(|i| sum / 3 + usize::from(i < sum % 3)); + Axis { step, pad: sum + 1, radii } + } + + fn blurs(&self) -> bool { + self.radii.iter().any(|&r| r > 0) } /// Grid pixels for `n` buffer pixels. @@ -156,7 +183,7 @@ fn coverage_at(ctx: &EvalCtx, layer: &Layer, g: &effectcraft_project::PropGroup, // rasterised on a grid padded by the blur's reach, blurred there and cropped to the buffer. // A variable feather scales its point radii by the mean scale: it stays at full resolution. let (ax, ay) = (Axis::new(feather[0] * buf.scale, linear, variable), Axis::new(feather[1] * buf.scale, linear, variable)); - let blurred = ax.blur > 0.0 || ay.blur > 0.0; + let blurred = ax.blurs() || ay.blurs(); let grid = match (ax.len(w), ay.len(h)) { (Some(gw), Some(gh)) if blurred && gw.checked_mul(gh).is_some_and(|n| n <= MAX_GRID_PX) => { let (Ok(gw), Ok(gh)) = (u32::try_from(gw), u32::try_from(gh)) else { return None }; @@ -182,9 +209,14 @@ fn coverage_at(ctx: &EvalCtx, layer: &Layer, g: &effectcraft_project::PropGroup, effectcraft_path::fill_coverage(std::slice::from_ref(&path), &mg, gw, gh, FillRule::NonZero) }; if blurred { - let img = cov.to_image(); - let b = if linear { box_blur(&img, gx.blur as usize, gy.blur as usize, 1, false) } else { gaussian_blur(&img, gx.blur, gy.blur, false) }; - cov = Mask::from_alpha(&b); + // Separable box passes (the corner of a feathered rect is the product of its edges). + let mut img = cov.to_image(); + for (rx, ry) in gx.radii.into_iter().zip(gy.radii) { + if rx > 0 || ry > 0 { + img = box_blur(&img, rx, ry, 1, false); + } + } + cov = Mask::from_alpha(&img); } if grid.is_some() { cov = crop(&cov, gx, gy, w, h); diff --git a/crates/render/src/tests_mask_feather.rs b/crates/render/src/tests_mask_feather.rs index 52ad60c61..db04b1f9f 100644 --- a/crates/render/src/tests_mask_feather.rs +++ b/crates/render/src/tests_mask_feather.rs @@ -26,18 +26,28 @@ fn add_mask(p: &mut Project, l: &mut Layer, rect: ShapePath, feather: [f64; 2], l.props.sub_mut("masks").unwrap().children.push(Node::Group(m)); } -/// The standard normal distribution function (Abramowitz and Stegun 7.1.26, error < 2e-7). -fn phi(x: f64) -> f64 { - let z = x.abs() / std::f64::consts::SQRT_2; - let t = 1.0 / (1.0 + 0.327_591_1 * z); - let poly = t * (0.254_829_592 + t * (-0.284_496_736 + t * (1.421_413_741 + t * (-1.453_152_027 + t * 1.061_405_429)))); - let erf = 1.0 - poly * (-z * z).exp(); - if x >= 0.0 { 0.5 * (1.0 + erf) } else { 0.5 * (1.0 - erf) } +/// Coverage at signed distance `d` inside an edge blurred by three box passes `w` pixels wide +/// (the Smooth falloff: an Irwin-Hall n = 3 distribution function, support +-1.5 w). +fn edge(d: f64, w: f64) -> f64 { + let t = (d / w + 1.5).clamp(0.0, 3.0); + if t < 1.0 { + t * t * t / 6.0 + } else if t < 2.0 { + (-2.0 * t * t * t + 9.0 * t * t - 9.0 * t + 3.0) / 6.0 + } else { + 1.0 - (3.0 - t).powi(3) / 6.0 + } } -/// Coverage at pixel centre `x` of the span `a..b` blurred by a Gaussian of `sigma` (one axis). -fn span(x: f64, a: f64, b: f64, sigma: f64) -> f64 { - phi((b - x) / sigma) - phi((a - x) / sigma) +/// The box window of the Smooth falloff for `feather` pixels: `2 round(0.37 feather) + 1`. +fn window(feather: f64) -> f64 { + 2.0 * (0.37 * feather).round() + 1.0 +} + +/// Coverage at pixel centre `x` of the span `a..b` feathered by `feather` (one axis). +fn span(x: f64, a: f64, b: f64, feather: f64) -> f64 { + let w = window(feather); + edge(x - a, w) + edge(b - x, w) - 1.0 } /// A white 200×100 solid (32 bpc) with one Add mask. @@ -54,15 +64,16 @@ fn white_with_mask(rect: ShapePath, feather: [f64; 2], linear: bool, scale: f64) #[test] fn a_feathered_mask_outside_a_solid_reaches_into_it() { - // The mask spans x 210..260, right of the layer (x 0..200); feather 40 = Gaussian sigma 20. + // The mask spans x 210..260, right of the layer (x 0..200); feather 40 = three 31 px boxes. let img = white_with_mask(ShapePath::rect([235.0, 50.0], 50.0, 200.0), [40.0, 40.0], false, 1.0); - for x in [150i64, 180, 199] { - let want = span(x as f64 + 0.5, 210.0, 260.0, 20.0) * span(50.5, -50.0, 150.0, 20.0); + for x in [150i64, 170, 180, 199] { + let want = span(x as f64 + 0.5, 210.0, 260.0, 40.0) * span(50.5, -50.0, 150.0, 40.0); let got = img.get(x, 50)[3] as f64; - assert!((got - want).abs() < 0.01, "x {x}: alpha {got}, the Gaussian gives {want}"); + assert!((got - want).abs() < 0.01, "x {x}: alpha {got}, the box kernel gives {want}"); } assert!(img.get(199, 50)[3] > 0.25, "the feather reaches the layer edge"); - assert!(img.get(100, 50)[3] < 1e-3); + // Finite support: nothing beyond 1.5 windows (46.5 px) from the edge. + assert!(img.get(160, 50)[3] == 0.0 && img.get(100, 50)[3] == 0.0); // Without feather the mask hides the layer. let hard = white_with_mask(ShapePath::rect([235.0, 50.0], 50.0, 200.0), [0.0, 0.0], false, 1.0); assert!(hard.data.iter().all(|p| p[3] == 0.0)); @@ -151,23 +162,21 @@ fn case_398_a_feathered_mask_below_an_adjustment_layer_reaches_into_it() { let mut report = Vec::new(); for ((x, y), want_ae) in ae { let got = rgb8(&img, x, y); - // 1. The fix: the coverage is the mask's Gaussian (sigma = feather / 2 = 500), blurred from - // the mask edge outside the layer; the result is the red mixed toward the ramp by it. - let c = span(x as f64 + 0.5, 0.0, 1920.0, 500.0) * span(y as f64 + 0.5, 1150.0, 1350.0, 500.0); + // 1. The coverage is the mask's Smooth falloff (three 741 px boxes for feather 1000), + // blurred from the mask edge outside the layer (on the coarse grid); the result is the + // red mixed toward the ramp by it. + let c = span(x as f64 + 0.5, 0.0, 1920.0, 1000.0) * span(y as f64 + 0.5, 1150.0, 1350.0, 1000.0); let r = ramp.get(x, y); let want = [0, 1, 2].map(|k| { let red = if k == 0 { 1.0 } else { 0.0 }; ((red + (r[k] as f64 - red) * c) * 255.0).round() as i32 }); for k in 0..3 { - assert!((got[k] - want[k]).abs() <= 3, "({x}, {y}): {got:?}, the Gaussian coverage {c:.4} gives {want:?}"); + assert!((got[k] - want[k]).abs() <= 2, "({x}, {y}): {got:?}, the box coverage {c:.4} gives {want:?}"); } - // 2. After Effects: the same shape of falloff, the feather reaching ~500 px into the layer. - // Its kernel is narrower than sigma = feather / 2 (the AE values fit sigma ~ 350), so - // near the mask EffectCraft is lower and far from it higher: 12 levels apart at most - // (green at the bottom edge), allowed 14. + // 2. After Effects: within 2 levels per channel. for k in 0..3 { - assert!((got[k] - want_ae[k]).abs() <= 14, "({x}, {y}): EffectCraft {got:?}, After Effects {want_ae:?}"); + assert!((got[k] - want_ae[k]).abs() <= 2, "({x}, {y}): EffectCraft {got:?}, After Effects {want_ae:?}"); } report.push(format!("({x},{y}) ec {got:?} ae {want_ae:?}")); } @@ -176,3 +185,67 @@ fn case_398_a_feathered_mask_below_an_adjustment_layer_reaches_into_it() { assert!(rgb8(&img, 960, 0)[0] >= 253 && rgb8(&img, 960, 0)[1] == 0); assert!(rgb8(&img, 960, 1079)[1] > 25, "the feather reaches the bottom edge"); } + +/// After Effects 2026 (sRGB, 32 bpc): a red 1920x1080 solid with a 1000x600 Add mask centred at +/// [960, 540] (left edge at x 460), feather `f` on both axes; coverage along the row y 540 from +/// x 160 to 760 in steps of 20 (8-bit values / 255). +const AE_FEATHER_100: [(i64, f64); 11] = + [(360, 0.0), (380, 0.016), (400, 0.059), (420, 0.153), (440, 0.31), (460, 0.506), (480, 0.698), (500, 0.855), (520, 0.945), (540, 0.988), (560, 1.0)]; +const AE_FEATHER_300: [(i64, f64); 31] = [ + (160, 0.0), + (180, 0.004), + (200, 0.008), + (220, 0.012), + (240, 0.024), + (260, 0.035), + (280, 0.055), + (300, 0.078), + (320, 0.11), + (340, 0.149), + (360, 0.192), + (380, 0.247), + (400, 0.306), + (420, 0.369), + (440, 0.435), + (460, 0.502), + (480, 0.569), + (500, 0.635), + (520, 0.698), + (540, 0.757), + (560, 0.808), + (580, 0.851), + (600, 0.89), + (620, 0.922), + (640, 0.945), + (660, 0.965), + (680, 0.976), + (700, 0.988), + (720, 0.992), + (740, 0.996), + (760, 1.0), +]; + +#[test] +fn the_smooth_feather_falloff_matches_after_effects() { + for (f, ae) in [(100.0, &AE_FEATHER_100[..]), (300.0, &AE_FEATHER_300[..])] { + let mut p = Project::default(); + p.settings.bit_depth = BitDepth::Bpc32; + let comp = Comp::new(1920, 1080, FrameRate::FPS_30, Tick::from_seconds_f64(1.0)); + let cid = p.add_item("Comp", Label::Sandstone, None, ItemKind::Comp(comp.clone().into())); + let mut l = solid(&mut p, &comp, [1.0, 0.0, 0.0], 1920, 1080); + add_mask(&mut p, &mut l, ShapePath::rect([960.0, 540.0], 1000.0, 600.0), [f, f], false); + p.comp_mut(cid).unwrap().layers.push(l); + let img = render_frame(&p, cid, Tick::ZERO, 1.0); + let mut worst = 0.0f64; + for &(x, want) in ae { + let got = img.get(x, 540)[3] as f64; + // Tolerance 2/255 on the 8-bit After Effects values. + assert!((got - want).abs() <= 2.0 / 255.0, "feather {f}, x {x}: {got:.4}, After Effects {want}"); + worst = worst.max((got - want).abs()); + } + // The corner is the product of its two edges (a separable blur): 0.25 for both feathers. + let corner = img.get(460, 240)[3] as f64; + assert!((corner - 0.251).abs() <= 2.0 / 255.0, "feather {f}: corner {corner}"); + println!("feather {f}: largest deviation from After Effects {:.2}/255", worst * 255.0); + } +}