Optimizing Bloom and Anamorphic Lens Flare Passes in WebGL
Implementing energy-conserving dual-kawase downsampling and bright-pass threshold filters for cinematic lighting effects in 3D web applications.
Cinematic bloom effects make high-intensity light sources pop against dark backgrounds. Standard Gaussian blurs require multiple texture lookups, whereas dual-kawase filtering achieves smooth wide-radius bloom efficiently.
1. Bright-Pass Luminance Threshold Extraction
Fragment shaders extract pixels exceeding specific HDR luminance thresholds, isolating bright specular reflections and emissive materials before applying downsampling blur chains.
2. Dual-Kawase Downsampling & Upsampling Pyramids
Iteratively downsampling framebuffers into half-resolution mipmaps and upsampling them back with tent-filter kernels generates wide, artifact-free bloom glows while minimizing GPU texture bandwidth.
3. Anamorphic Streak Lens Flares
Stretching bloom sampling kernels horizontally across specific color channels reproduces sci-fi anamorphic lens flare streaks common in automotive and architectural rendering packages.