Function apply_transmission_hack

native/shared/src/models.rs:1790–1804

Fake KHR_materials_transmission as a near-mirror dielectric. We don't implement real refractive transmission (no back-buffer refraction pass, no thin-walled/volume distinction), so a transmission=0.9 glass pane loads as a plain diffuse white surface that drowns the 4% Fresnel specular in a bright diffuse term — the classic "painted white window" look. As a stand-in we force heavy transmission ma

(
    transmission: f32,
    base_color: &mut [f32; 4],
    metallic: &mut f32,
    roughness: &mut f32,
)

/// normal incidence — but it matches how windows *read* in photos
/// (reflecting sky/buildings) far better than a flat diffuse surface.
fn apply_transmission_hack(
    transmission: f32,
    base_color: &mut [f32; 4],
    metallic: &mut f32,
    roughness: &mut f32,
) {
    if transmission > 0.5 {
        *metallic = 1.0;
        *roughness = roughness.min(0.05);
        base_color[0] *= 0.85;
        base_color[1] *= 0.85;
        base_color[2] *= 0.85;
        base_color[3] = 1.0;
    }
}

/// Reference: Khronos glTF sample specGloss→metallicRoughness
/// converter (https://github.com/KhronosGroup/glTF/pull/1355).