@@ -379,7 +379,7 @@ export material gltf_material(
379379 // KHR_materials_ior
380380 uniform float ior = 1.5
381381 [[
382- anno::hard_range (1.00 , 5.0),
382+ anno::soft_range (1.0 , 5.0),
383383 anno::in_group("Metallic Roughness"),
384384 anno::display_name("IOR"),
385385 anno::description("The index of refraction.")
@@ -474,6 +474,50 @@ export material gltf_material(
474474 anno::enable_if("clearcoat_factor>0.0")
475475 ]],
476476
477+ // KHR_materials_iridescence
478+ uniform float iridescence_factor = 0.0
479+ [[
480+ anno::hard_range(0.0, 1.0),
481+ anno::in_group("Iridescence"),
482+ anno::display_name("Iridescence Factor"),
483+ anno::description("Strength of the iridescence. Multiplied to the 'Iridescence Texture' if available.")
484+ ]],
485+ gltf_texture_lookup_value iridescence_texture = gltf_texture_lookup()
486+ [[
487+ anno::in_group("Iridescence"),
488+ anno::display_name("Iridescence Texture"),
489+ anno::description("Strength of the iridescence. Uses only the red channel, assuming linear space. Influenced by the 'Iridescence Factor'."),
490+ anno::enable_if("iridescence_factor>0")
491+ ]],
492+ uniform float iridescence_ior = 1.3
493+ [[
494+ anno::soft_range(1.0, 5.0),
495+ anno::in_group("Iridescence"),
496+ anno::display_name("Iridescence IOR"),
497+ anno::description("The index of refraction of the dielectric thin-film layer.")
498+ ]],
499+ uniform float iridescence_thickness_minimum = 100
500+ [[
501+ anno::soft_range(0.0, 600.0),
502+ anno::in_group("Iridescence"),
503+ anno::display_name("Iridescence Thickness Minimum"),
504+ anno::description("The minimum thickness of the thin-film layer given in nanometers.")
505+ ]],
506+ uniform float iridescence_thickness_maximum = 400
507+ [[
508+ anno::soft_range(0.0, 1000.0),
509+ anno::in_group("Iridescence"),
510+ anno::display_name("Iridescence Thickness Maximum"),
511+ anno::description("The maximum thickness of the thin-film layer given in nanometers. Used as thickness if no 'Iridescence Thickness Texture' if available.")
512+ ]],
513+ gltf_texture_lookup_value iridescence_thickness_texture = gltf_texture_lookup()
514+ [[
515+ anno::in_group("Iridescence"),
516+ anno::display_name("Iridescence Thickness Texture"),
517+ anno::description("The thickness texture of the thin-film layer. Uses only the red channel, assuming linear space. Used to blend between 'Iridescence Thickness Minimum' and 'Iridescence Thickness Maximum'."),
518+ anno::enable_if("iridescence_factor>0")
519+ ]],
520+
477521 // emission
478522 uniform color emissive_factor = color(0.0)
479523 [[
@@ -568,7 +612,7 @@ export material gltf_material(
568612 // ------------------------------------------------------------------------
569613 float4 base_float4 = gltf_prepare_tex_float4(base_color_texture) * scene::data_lookup_float4("COLOR_0", float4(1.0)); // apply vertex color
570614 color base_color = base_color_factor * color(base_float4.x, base_float4.y, base_float4.z);
571- float alpha = base_alpha * base_float4.w;
615+ float alpha = base_alpha * math::pow( base_float4.w, 1.0/2.2) ;
572616
573617 float3 metallic_roughness = gltf_prepare_tex_float3(metallic_roughness_texture);
574618 float metallic = metallic_factor * metallic_roughness.z;
@@ -600,6 +644,11 @@ export material gltf_material(
600644 float3 clearcoat_normal = gltf_prepare_normal(clearcoat_normal_texture);
601645 float grazing_refl_coat = math::max((1.0 - clearcoat_roughness), 0.0);
602646
647+ // KHR_materials_iridescence
648+ // ------------------------------------------------------------------------
649+ float iridescence_strength = gltf_prepare_tex_float3(iridescence_texture).x * iridescence_factor;
650+ float iridescence_thickness = math::lerp(iridescence_thickness_minimum, iridescence_thickness_maximum, gltf_prepare_tex_float3(iridescence_thickness_texture).x);
651+
603652 // metallic roughness model
604653 // ------------------------------------------------------------------------
605654
@@ -630,13 +679,41 @@ export material gltf_material(
630679 normal: normal
631680 );
632681
633- // the metallic component doesn't have a diffuse component,
682+ // apply iridescence and make the strength adjustable using a weighted layer
683+ bsdf dielectric_component_with_thin_film = df::weighted_layer(
684+ weight: iridescence_strength,
685+ base: dielectric_component,
686+ layer: df::thin_film(
687+ thickness: iridescence_thickness,
688+ ior: color(iridescence_ior),
689+ base: dielectric_component
690+ )
691+ );
692+
693+ // the metallic component doesn't have a diffuse component,
634694 // its only glossy base_color is applied to tint it
635695 bsdf metallic_component = df::microfacet_ggx_vcavities_bsdf(
636- tint: base_color * occlusion,
696+ tint: base_color * occlusion,
637697 roughness_u: roughness2);
638698
639- // apply sheen to the dielectic component
699+ // apply iridescence and make the strength adjustable using a weighted layer
700+ // according to KHR_materials_iridescence spec: using dielectric thin film fresnel for metals, too
701+ color base_color_sqrt = math::min(math::sqrt(math::saturate(base_color * occlusion)), color(0.99f));
702+ color dielectric_ior = (color(1.0f) + base_color_sqrt) / (color(1.0f) - base_color_sqrt);
703+ bsdf metallic_component_with_thin_film = df::weighted_layer(
704+ weight: iridescence_strength,
705+ base: metallic_component,
706+ layer: df::thin_film(
707+ thickness: iridescence_thickness,
708+ ior: color(iridescence_ior),
709+ base: df::fresnel_factor(
710+ ior: dielectric_ior,
711+ extinction_coefficient: color(0.0f),
712+ base: df::microfacet_ggx_vcavities_bsdf(roughness_u: roughness2))
713+ )
714+ );
715+
716+ // apply sheen to the dielectric component
640717 // add the sheen_color as weight in an outer layer to be able to blend and disable on default
641718 // otherwise, sheen would be applied and tinted black
642719 bsdf dielectric_sheen_component = df::color_weighted_layer(
@@ -645,15 +722,15 @@ export material gltf_material(
645722 roughness: sheen_roughness * sheen_roughness,
646723 tint: color(1.0),
647724 multiscatter_tint: color(1.0),
648- multiscatter: dielectric_component
725+ multiscatter: dielectric_component // don't apply thin_film
649726 ),
650- base: dielectric_component );
727+ base: dielectric_component_with_thin_film );
651728
652729 // final BSDF is a linear blend between dielectric and metallic component
653730 bsdf dielectric_metal_mix = df::weighted_layer(
654731 weight: metallic,
655732 base: dielectric_sheen_component,
656- layer: metallic_component ,
733+ layer: metallic_component_with_thin_film ,
657734 normal: normal);
658735
659736 bsdf clearcoated = df::custom_curve_layer(
@@ -806,11 +883,11 @@ export material gltf_material_khr_specular_glossiness(
806883 // ------------------------------------------------------------------------
807884 float4 diffuse_float4 = gltf_prepare_tex_float4(diffuse_texture) * scene::data_lookup_float4("COLOR_0", float4(1.0)); // apply vertex color
808885 color diffuse = diffuse_factor * color(diffuse_float4.x, diffuse_float4.y, diffuse_float4.z);
809- float alpha = base_alpha * diffuse_float4.w;
886+ float alpha = base_alpha * math::pow( diffuse_float4.w, 1.0/2.2) ;
810887
811888 float4 specular_glossiness = gltf_prepare_tex_float4(specular_glossiness_texture);
812889 color specular = specular_factor * color(specular_glossiness.x, specular_glossiness.y, specular_glossiness.z);
813- float glossiness = glossiness_factor * specular_glossiness.w;
890+ float glossiness = glossiness_factor * math::pow( specular_glossiness.w, 1.0/2.2) ;
814891
815892 float3 normal = gltf_prepare_normal(normal_texture);
816893 float occlusion = gltf_prepare_occlusion(occlusion_texture, occlusion_strength);
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