实时文本模式引擎

Render your scene into an offscreen framebuffer at grid resolution (one texel per character cell). Bake a font atlas texture containing a brightness-sorted list of glyphs. In a fragment shader on the full-size canvas, find which cell the fragment belongs to, sample the low-res buffer for that cell's luminance and color, choose the glyph index from luminance, and sample the atlas at the fragment's position inside the cell. Expose a small immediate-mode API (rect, char, fill, rotate) that writes into the low-res buffer so users can draw directly in cell space.