manual_slop/conductor/tracks/frosted_glass_20260313/spec.md

Specification: Frosted Glass Background Effect (REPAIR - TRUE GPU)

Overview

Implement a high-fidelity "frosted glass" (acrylic) background effect using a dedicated OpenGL pipeline. This implementation follows professional rendering patterns (downsampling, multi-pass blurring, and screen-space sampling) to ensure a smooth, milky look that remains performant on high-DPI displays.

Functional Requirements

• Dedicated Background Pipeline:
  • Render the animated "Deep Sea" background shader to an off-screen SceneFBO once per frame.
• Multi-Scale Downsampled Blur:
  • Downsample the SceneFBO texture to 1/4 or 1/8 resolution.
  • Perform 2-pass Gaussian blurring on the downsampled texture to achieve a creamy "milky" aesthetic.
• ImGui Panel Integration:
  • Each ImGui panel must sample its background from the blurred texture using screen-space UV coordinates.
  • Automatically force window transparency (alpha 0.0) when the effect is active.
• Real-Time Shader Tuning:
  • Control blur radius, tint intensity, and opacity via the Live Shader Editor.
• Stability:
  • Balanced style-stack management to prevent ImGui assertion crashes.
  • Strict 1-space indentation and class scope protection.

Technical Implementation

• FBO Management: Persistent FBOs for scene, temp, and blur textures.
• UV Math: (window_pos / screen_res) mapping to handle high-DPI scaling and vertical flipping.
• DrawList Callbacks: (If necessary) use callbacks to ensure the background is ready before panels draw.

Acceptance Criteria

• Toggling the effect does not crash the app.
• Windows show a deep, high-quality blur of the background shader.
• Blur follows windows perfectly during drag/resize.
• The "Milky" look is highly visible even at low radii.