UI Enhancement: SDF Font Rendering for Smooth Scaling

[MichaelFisher1997]

Summary

Currently, the engine uses a 5x7 pixel bitmap font rendered as individual rectangles. While this provides a retro aesthetic, it becomes pixelated when scaled up on high-resolution displays.

This issue tracks the investigation and potential implementation of Signed Distance Field (SDF) fonts for smooth, resolution-independent text rendering.

Background

This was identified during the UI readability investigation in Issue #113. The manual UI scaling feature addresses immediate usability concerns, but SDF fonts would provide a more polished visual experience.

Current State

• Font system: src/engine/ui/font.zig - 5x7 bitmap glyphs stored as bit patterns
• Rendering: Each "pixel" of text is a solid rectangle drawn via RHI
• Scaling: Text scales linearly but remains blocky (intentional retro style)

Proposed Investigation

Option 1: SDF Font Rendering

• Pre-generate SDF textures from a TTF font (e.g., using msdfgen)
• Render text as textured quads with SDF shader
• Provides smooth edges at any scale with minimal texture memory

Option 2: stb_truetype Integration

• Runtime TTF parsing and rasterization
• More flexible but higher runtime cost
• Would require glyph caching system

Option 3: Hybrid Approach

• Keep bitmap font for small/retro UI elements
• Add SDF font option for larger text (titles, HUD)
• User setting to choose style

Implementation Considerations

1. Shader changes: Need fragment shader for SDF rendering
2. Texture atlas: Generate SDF atlas at build time or runtime
3. Glyph metrics: Need proper kerning/advance data from TTF
4. Memory: SDF atlas is typically 512x512 or 1024x1024

Acceptance Criteria

• Research complete: chosen approach documented
• SDF font renders smoothly at 0.5x to 4x scale
• No visual regression for existing bitmap font users
• Performance impact < 1ms per frame for typical text rendering

Related

• Issue UI Readability Investigation: Bitmap Font and HiDPI Improvements #113 (UI Readability Investigation)
• Issue Vulkan Optimization: Fix Resolution, Add MSAA & Anisotropic Filtering #112 (Vulkan Optimization)

[MichaelFisher1997]

we moved to imGUI and its gone well, closing this