Method sample_metallic_roughness

tools/bloom-reference/src/main.rs:245–259

Sample metallic-roughness texture. The glTF convention packs occlusion in R, roughness in G, metallic in B; values are LINEAR (no sRGB decode). When no texture is present, falls back to the material's scalar factors alone.

(&self, material: &Material, uv: Vec2)

    /// LINEAR (no sRGB decode). When no texture is present, falls back
    /// to the material's scalar factors alone.
    fn sample_metallic_roughness(&self, material: &Material, uv: Vec2) -> (f32, f32) {
        let (metallic_factor, roughness_factor) = (material.metallic, material.roughness);
        let tex_idx = match material.metallic_roughness_texture {
            Some(i) => i as usize,
            None => return (metallic_factor, roughness_factor),
        };
        let (r, g, b) = match self.sample_texture_linear(tex_idx, uv) {
            Some(c) => c,
            None => return (metallic_factor, roughness_factor),
        };
        let _ = r; // occlusion — ignored here, sampled separately if needed
        let roughness = g * roughness_factor;
        let metallic = b * metallic_factor;
        (metallic, roughness)
    }

    /// Sample emissive texture × factor. Emissive textures are sRGB-
    /// encoded per the glTF spec.