Struct SdfAtlas 

pub struct SdfAtlas {
    pub pixels: Vec<u8>,
    pub width: u32,
    pub height: u32,
    pub channels: u32,
    pub glyph_metrics: HashMap<char, SdfGlyphMetric>,
    pub sdf_spread: f32,
    pub font_size_px: f32,
}

A font atlas using Signed Distance Fields for resolution-independent rendering.

Each pixel in the atlas stores the signed distance to the nearest glyph edge:

• 128 (0.5 normalized) = exactly on the edge
• 255 (1.0 normalized) = deep inside the glyph
• 0 (0.0 normalized) = far outside the glyph

The fragment shader thresholds this distance to produce a crisp edge at any resolution, rotation, or scale.

Fields

pixels: Vec<u8>

R8 pixel data (each pixel = distance value).

width: u32

Atlas dimensions.

height: u32

channels: u32

Number of channels: 1 for SDF, 3 for MSDF.

glyph_metrics: HashMap<char, SdfGlyphMetric>

Per-glyph metrics and UV coordinates.

sdf_spread: f32

How many output pixels the distance field extends (typically 8.0).

font_size_px: f32

The font size at which the SDF was generated (typically 64px).

Implementations

impl SdfAtlas

pub fn build() -> Self

Build an SDF atlas with default configuration.

pub fn build_with_config(config: &SdfConfig) -> Self

Build an SDF atlas with custom configuration.

pub fn from_atlas_data(data: SdfAtlasData) -> Self

Build from pre-computed atlas data.

pub fn metric_for(&self, ch: char) -> SdfGlyphMetric

Get the metric for a character, falling back to ‘?’ then a default.

pub fn uv_for(&self, ch: char) -> [f32; 4]

Get the UV rect as [u_min, v_min, u_max, v_max].

pub fn uv_offset(&self, ch: char) -> [f32; 2]

Get the UV offset (top-left corner) as [u, v].

pub fn uv_size(&self, ch: char) -> [f32; 2]

Get the UV size as [u_width, v_height].

pub fn compute_smoothing( &self, screen_px_per_unit: f32, glyph_scale: f32, ) -> f32

Compute the smoothing factor for SDF rendering based on the glyph’s screen-space size.

At large scales, the smoothing is very small → razor-sharp edges. At small scales, the smoothing is larger → anti-aliased edges.

screen_px_per_unit is how many screen pixels one world unit occupies. glyph_scale is the scale multiplier on the glyph.

pub fn threshold(&self) -> f32

Compute the threshold for SDF rendering.

Default is 0.5 (on the edge). Lower values make glyphs bolder, higher values make them thinner.

pub fn bold_threshold(&self) -> f32

Compute the threshold for a bold variant.

pub fn outline_range(&self, outline_width: f32) -> (f32, f32)

Compute the outline range for a given outline width (in SDF-space units).

Returns (inner_threshold, outer_threshold) for the outline smoothstep.

pub fn shadow_uv_offset(&self, shadow_offset: Vec2, glyph_scale: f32) -> Vec2

Compute the shadow UV offset for a drop shadow effect.

shadow_offset is in screen pixels, glyph_scale is the current scale.

pub fn glyph_count(&self) -> usize

Total number of glyphs in the atlas.

pub fn has_char(&self, ch: char) -> bool

Check if a character is available in the atlas.

pub fn measure_string_width(&self, text: &str, scale: f32) -> f32

Measure the width of a string in world units at a given scale.

pub fn line_height(&self, scale: f32) -> f32

Measure the height of a single line of text in world units at a given scale.