Fonts

Fonts are rasterized to atlas textures and rendered by TextPass. They are registered with ResourceManager as FontDescriptors and loaded asynchronously like other resource types.

Registration

auto res = ResourceManager::get();

res->register_font(FontDescriptor::create(
    "roboto",
    "fonts/Roboto-Regular.ttf"_engine,
    /* atlas_size */ 512,
    /* base_size */  48
));

Descriptor Fields

Field	Type	Description
id	std::string	Unique identifier
path	Path	Engine-relative path to the .ttf / .otf file
atlas_size	uint32_t	Width and height of the generated texture atlas in pixels
base_size	uint32_t	Point size used when rasterizing glyphs into the atlas

Larger base_size values produce sharper text at large display sizes but consume more atlas space. A 512×512 atlas at 48pt covers the full printable ASCII range.

Uploading

res->load_from_descriptors<FontDescriptor>(RendererBackend::OpenGL);

During upload, the font file is parsed, glyphs are rasterized to a CPU-side bitmap, and the result is uploaded to GPU as a Texture2D atlas. Per-glyph metrics (advance, bearing, UV rect) are stored alongside the atlas handle.

Rendering Text

Text is rendered by adding a text entity to the scene:

// In Scene::start()
auto* label = add_entity<Text>("FPSLabel");
label->content  = "Hello, Astra!";
label->font_id  = "roboto";
label->position = glm::vec2(16.0f, 16.0f);
label->scale    = 1.0f;
label->color    = glm::vec4(1.0f);

TextPass collects all text entities each frame, batches their quads per font atlas, and issues a single draw call per atlas.

Atlas Layout

Multi-Font Scenes

Each unique font_id maps to a separate atlas. TextPass sorts entities by font before batching, so switching fonts mid-scene does not break instancing within a single font.

Supported Formats

Format	Support
TrueType (.ttf)	Supported
OpenType (.otf)	Supported
Bitmap fonts	Not supported