materials/SimPBR_Translucent.mdl

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*     Copyright 1986-2020 NVIDIA Corporation. All rights reserved.
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 MDL MATERIALS ARE PROVIDED PURSUANT TO AN END USER LICENSE  AGREEMENT,
 WHICH WAS ACCEPTED IN ORDER TO GAIN ACCESS TO THIS FILE.  IN PARTICULAR,
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mdl 1.6;

import ::df::*;
import ::state::*;
import ::math::*;
import ::base::*;
import ::tex::*;
import ::anno::*;

import ::nvidia::core_definitions::file_texture;
import ::nvidia::core_definitions::normalmap_texture;

export material SimPBR_Translucent(
    // -------------------- SPECULAR REFLECTION/TRANSMISSION ----------------------
    uniform float ior_constant = 1.1f
    [[
        anno::display_name("Index of Refraction"),
        anno::hard_range(0.0,5.),
        anno::description("Index of Refraction of the material"),
        anno::in_group("Specular")
    ]],
    uniform float reflection_roughness_constant = 0.5f
    [[
        anno::display_name("Roughness Amount"),
        anno::hard_range(0.0,1.),
        anno::description("Higher roughness values lead to more blurry reflections"),
        anno::in_group("Specular")
    ]],
    uniform float reflection_roughness_texture_influence = 0.0f
    [[
        anno::display_name("Roughness Map Influence"),
        anno::hard_range(0.0, 1.),
        anno::description("Blends between the constant value and the lookup of the roughness texture"),
        anno::in_group("Specular")
    ]],
    uniform texture_2d reflectionroughness_texture = texture_2d()
    [[
        anno::display_name("Roughness Map"),
        anno::in_group("Specular")
    ]],

    // -------------------- VOLUME ----------------------
    color transmittance_color = color(1.0, 1.0f, 1.0f)
    [[
        anno::display_name("Transmittance Color"),
        anno::description("Expected transmittance after the specified transmittance distance through the volume."),
        anno::in_group("Volume")
    ]],
    float transmittance_measurement_distance = 1.0f
    [[
        anno::display_name("Transmittance Measurement Distance"),
        anno::description("Distance to match the transmittance through the volume at."),
        anno::in_group("Volume")
    ]],

    // -------------------- EMISSIVE ----------------------
    uniform bool enable_thin_walled = false
    [[
        anno::display_name("Enable Thin Walled"),
        anno::description("Enables thin walled logic"),
        anno::in_group("Geometry")
    ]],

    // -------------------- EMISSIVE ----------------------
    uniform bool enable_emission = false
    [[
        anno::display_name("Enable Emission"),
        anno::description("Enables the emission of light from the material"),
        anno::in_group("Emissive")
    ]],
    color emissive_color = color(1.0, 0.1, 0.1)
    [[
        anno::enable_if("enable_emission == true"),
        anno::display_name("Emissive Color"),
        anno::description("The emission color"),
        anno::in_group("Emissive")
    ]],
    uniform texture_2d emissive_mask_texture = texture_2d()
    [[
        anno::enable_if("enable_emission == true"),
        anno::display_name("Emissive Mask Map"),
        anno::description("The texture masking the emissive color"),
        anno::in_group("Emissive")
    ]],
    uniform float emissive_intensity = 40.f
    [[
        anno::enable_if("enable_emission == true"),
        anno::display_name("Emissive Intensity"),
        anno::description("Intensity of the emission"),
        anno::in_group("Emissive")
    ]],
    uniform bool enable_emissive_flipbook = false
    [[
        anno::display_name("Enable Flipbook for emission"),
        anno::description("Allows the use of animated emissive textures (e.g. video screens)"),
        anno::in_group("Emissive")
    ]],
    uniform int2 flipbook_dim = int2(1,1)
    [[
        anno::enable_if("enable_emissive_flipbook == true"),
        anno::display_name("Flipbook Rows/Columns"),
        anno::description("How many rows and columns are in the flipbook?"),
        anno::in_group("Emissive")
    ]],
    uniform int target_fps = 1
    [[
        anno::enable_if("enable_emissive_flipbook == true"),
        anno::display_name("Flipbook Target FPS"),
        anno::description("Playback speed in frames per second"),
        anno::in_group("Emissive")
    ]],

    // -------------------- NORMAL ----------------------
    uniform float bump_factor = 1.f
    [[
        anno::display_name("Normal Map Strength"),
        anno::description("Strength of normal map."),
        anno::in_group("Normal")
    ]],
    uniform texture_2d normalmap_texture = texture_2d()
    [[
        anno::display_name("Normal Map"),
        anno::in_group("Normal")
    ]],
    uniform bool flip_tangent_u = false
    [[
        anno::display_name("Normal Map Flip U Tangent"),
        anno::in_group("Normal")
    ]],
    uniform bool flip_tangent_v = true
    [[
        anno::display_name("Normal Map Flip V Tangent"),
        anno::in_group("Normal")
    ]],

    // -------------------- UV ADJUSTMENTS ----------------------
    uniform bool project_uvw = false
    [[
        anno::display_name("Enable Project UVW Coordinates"),
        anno::description("When enabled, UV coordinates will be generated by projecting them from a coordinate system"),
        anno::in_group("UV")
    ]],
    uniform bool world_or_object = false
    [[
        anno::enable_if("project_uvw == true"),
        anno::display_name("Enable World Space"),
        anno::description("When set to 'true' uses world space for projection, when 'false' object space is used"),
        anno::in_group("UV")
    ]],
    uniform float2 texture_translate =  float2(0.0f)
    [[
        anno::display_name("Texture Translate"),
        anno::description("Controls position of texture."),
        anno::in_group("UV")
    ]],
    uniform float2 texture_scale =  float2(1.0f)
    [[
        anno::display_name("Texture Tiling"),
        anno::description("Controls the repetition of the texture."),
        anno::in_group("UV")
    ]],
    uniform float2 texture_speed =  float2(0.0f)
    [[
        anno::display_name("Texture Speed"),
        anno::description("Scrolling texture animation speed in UVs per sec."),
        anno::in_group("UV")
    ]]
)
[[    anno::display_name("Sim PBR Translucent"),    anno::description("Supports the translucent material model of the Sim Renderer"),    anno::in_group("SimReady"),    anno::version( 1, 0, 0),    anno::author("NVIDIA CORPORATION"),    anno::key_words(string[]("Sim", "PBR", "translucent", "omniverse", "generic"))
]]
 = let {
    base::texture_coordinate_system the_system = world_or_object ? base::texture_coordinate_world : base::texture_coordinate_object;

    base::texture_coordinate_info uvw = project_uvw ?
        base::coordinate_projection(
            coordinate_system: the_system,
            texture_space: 0,
            projection_type: base::projection_cubic
        ) : base::coordinate_source(
            coordinate_system: base::texture_coordinate_uvw,
            texture_space: 0
        );

    // Need to use a small value so the compiler doesnt optimize out this var...
    float t = 0.00000001;//state::animation_time();
    base::texture_coordinate_info transformed_uvw =  base::transform_coordinate(
        transform: base::rotation_translation_scale(
        scaling: float3(texture_scale.x, texture_scale.y, 1.0),
        rotation: float3(0.0, 0.0, 0.0 ),
        translation: float3(texture_translate.x + t * texture_speed.x, texture_translate.y + t * texture_speed.y, 0.0)),
        coordinate: uvw
    );
    float2 uv = float2(transformed_uvw.position.x, transformed_uvw.position.y);

    color volume_absorption_coefficient = -math::log(transmittance_color) / (transmittance_measurement_distance*0.01);

    float roughness_lookup = tex::texture_isvalid(reflectionroughness_texture) ?
        tex::lookup_float4(tex: reflectionroughness_texture, coord: uv).x : reflection_roughness_constant;
    float reflection_roughness =  math::lerp(reflection_roughness_constant, roughness_lookup, reflection_roughness_texture_influence);

    float roughness_squared = reflection_roughness * reflection_roughness;
    bsdf final_bsdf(enable_thin_walled ?
        ::df::fresnel_layer(
            ior_constant,
            1.f,
            ::df::microfacet_ggx_smith_bsdf(
                roughness_squared,
                roughness_squared,
                color(1.f, 1.f, 1.f),
                color(0.f, 0.f, 0.f),
                ::state::texture_tangent_u(0),
                ::df::scatter_reflect,
                ""
            ),
            ::df::specular_bsdf(
                transmittance_color,
                ::df::scatter_transmit,
                ""
            ), ::state::normal())
    : ::df::microfacet_ggx_smith_bsdf(
        roughness_squared,
        roughness_squared,
        color(1.f, 1.f, 1.f),
        color(0.f, 0.f, 0.f),
        ::state::texture_tangent_u(0),
        ::df::scatter_reflect_transmit,
        ""
    ));

    int rows = flipbook_dim.x;
    int columns = flipbook_dim.y;
    int numFrames = rows * columns;
    varying int frameIdx = int(state::animation_time() * target_fps) % numFrames;
    varying float2 baseUV = float2(transformed_uvw.position.x, transformed_uvw.position.y);
    varying float2 emissiveUV = enable_emissive_flipbook ?
        ((baseUV + float2(frameIdx % rows, frameIdx / rows)) / float2(rows, columns)) : baseUV;

    color emissive_mask = tex::texture_isvalid(emissive_mask_texture) ?
        tex::lookup_color(emissive_mask_texture, emissiveUV, tex::wrap_repeat, tex::wrap_repeat) : color(1.0);

    // Normal calculations
    float3 normal_lookup =  tex::texture_isvalid(normalmap_texture) ?
        base::tangent_space_normal_texture(
            texture: normalmap_texture,
            factor: bump_factor,
            uvw: transformed_uvw,
            flip_tangent_u: flip_tangent_u,
            flip_tangent_v: flip_tangent_v
        ) : state::normal();
} in material(
    thin_walled: enable_thin_walled,
    surface: material_surface(
        scattering: final_bsdf,
        emission: material_emission (
            df::diffuse_edf(),
            intensity: enable_emission ? emissive_color * emissive_mask * color(emissive_intensity) : color(0)
        )
    ),
    ior: color(ior_constant),
    volume: material_volume(
        scattering: df::anisotropic_vdf(),
        absorption_coefficient: volume_absorption_coefficient,
        scattering_coefficient: color(0.0f, 0.0f, 0.0f)
    ),
    geometry: material_geometry(
        normal: normal_lookup
    )
);