viewport-lib 0.14.0

3D viewport rendering library
Documentation 
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// tone_map.wgsl : fullscreen post-process composite: tone mapping, bloom, SSAO, contact shadows.
// Renders a fullscreen triangle (no vertex buffer) using vertex_index.

struct ToneMapUniform {
    exposure:                f32,
    mode:                    u32,  // 0=Reinhard, 1=ACES, 2=KhronosNeutral
    bloom_enabled:           u32,
    ssao_enabled:            u32,
    contact_shadows_enabled: u32,
    edl_enabled:             u32,
    edl_radius:              f32,
    edl_strength:            f32,
    background_colour:        vec4<f32>,
    near_plane:              f32,
    far_plane:               f32,
    lic_enabled:             u32,
    lic_strength:            f32,
}

@group(0) @binding(0) var hdr_texture:  texture_2d<f32>;
@group(0) @binding(1) var hdr_sampler:  sampler;
@group(0) @binding(2) var<uniform> params: ToneMapUniform;
@group(0) @binding(3) var bloom_texture: texture_2d<f32>;
@group(0) @binding(4) var ao_texture:    texture_2d<f32>;
@group(0) @binding(5) var cs_texture:    texture_2d<f32>;
@group(0) @binding(6) var depth_texture: texture_depth_2d;
@group(0) @binding(7) var lic_texture:   texture_2d<f32>;

struct VertexOutput {
    @builtin(position) pos: vec4<f32>,
    @location(0)       uv:  vec2<f32>,
}

@vertex
fn vs_main(@builtin(vertex_index) vi: u32) -> VertexOutput {
    let positions = array<vec2<f32>, 3>(
        vec2<f32>(-1.0, -1.0),
        vec2<f32>( 3.0, -1.0),
        vec2<f32>(-1.0,  3.0),
    );
    let p = positions[vi];
    let uv = vec2<f32>((p.x + 1.0) * 0.5, (1.0 - p.y) * 0.5);
    return VertexOutput(vec4<f32>(p, 0.0, 1.0), uv);
}

fn reinhard(x: vec3<f32>) -> vec3<f32> {
    return x / (x + vec3<f32>(1.0));
}

fn aces(x: vec3<f32>) -> vec3<f32> {
    return clamp(
        (x * (2.51 * x + 0.03)) / (x * (2.43 * x + 0.59) + 0.14),
        vec3<f32>(0.0),
        vec3<f32>(1.0),
    );
}

// Khronos PBR Neutral tone mapper (https://github.com/KhronosGroup/ToneMapping).
// Passes values below ~0.76 through with only a small black-point offset,
// then compresses highlights. Designed to preserve hand-authored SDR colours.
fn khronos_neutral(colour: vec3<f32>) -> vec3<f32> {
    let start_compression: f32 = 0.8 - 0.04;
    let desaturation: f32 = 0.15;

    let x = min(colour.r, min(colour.g, colour.b));
    let offset = select(x - 6.25 * x * x, 0.04, x < 0.08);
    let c = colour - offset;

    let peak = max(c.r, max(c.g, c.b));
    if peak < start_compression {
        return c;
    }

    let d = 1.0 - start_compression;
    let new_peak = 1.0 - d * d / (peak + d - start_compression);
    let scaled = c * (new_peak / peak);
    let g = 1.0 - 1.0 / (desaturation * (peak - new_peak) + 1.0);
    return mix(scaled, vec3<f32>(new_peak), g);
}

@fragment
fn fs_main(in: VertexOutput) -> @location(0) vec4<f32> {
    let depth_dims = textureDimensions(depth_texture);
    let depth_uv = clamp(in.uv, vec2<f32>(0.0), vec2<f32>(0.99999994));
    let depth_coord = vec2<i32>(vec2<u32>(depth_uv * vec2<f32>(depth_dims)));
    let depth = textureLoad(depth_texture, depth_coord, 0);
    if depth >= 0.999999 {
        // Check whether OIT has contributed to this pixel. The HDR buffer is
        // cleared with alpha=0; OIT composite writes alpha=(1-reveal) > 0 via
        // premul blend. If alpha is still ~0, this is a pure background pixel.
        let hdr_a = textureSample(hdr_texture, hdr_sampler, in.uv).a;
        if hdr_a < 0.001 {
            return params.background_colour;
        }
        // OIT contributed here; fall through to tone-map the composite result.
    }

    var colour = textureSample(hdr_texture, hdr_sampler, in.uv).rgb;

    // Add bloom additively before tone mapping.
    if params.bloom_enabled != 0u {
        let bloom = textureSample(bloom_texture, hdr_sampler, in.uv).rgb;
        colour = colour + bloom;
    }

    // Multiply by AO before tone mapping.
    if params.ssao_enabled != 0u {
        let ao = textureSample(ao_texture, hdr_sampler, in.uv).r;
        colour = colour * ao;
    }

    // Multiply by contact shadow factor before tone mapping.
    if params.contact_shadows_enabled != 0u {
        let cs = textureSample(cs_texture, hdr_sampler, in.uv).r;
        colour = colour * cs;
    }

    // Eye-Dome Lighting: darken pixels at depth discontinuities.
    // Depth is linearized (z_eye / far) before the log comparison so that the
    // log differences are large enough to produce a visible effect regardless
    // of the near/far plane ratio.
    if params.edl_enabled != 0u {
        let n = params.near_plane;
        let f = params.far_plane;
        // Linear depth in [near/far, 1]: z_eye/far = n / (f - d*(f-n))
        let lin_dc  = n / (f - depth * (f - n));
        let log_ldc = log(lin_dc);
        let dims_i  = vec2<i32>(depth_dims);
        let edl_r   = i32(max(1.0, round(params.edl_radius)));
        var edl_nc: vec2<i32>;
        var edl_sum = 0.0;
        edl_nc = clamp(depth_coord + vec2<i32>( edl_r,      0), vec2<i32>(0), dims_i - vec2<i32>(1));
        edl_sum += max(0.0, log(n / (f - textureLoad(depth_texture, edl_nc, 0) * (f - n))) - log_ldc);
        edl_nc = clamp(depth_coord + vec2<i32>( edl_r,  edl_r), vec2<i32>(0), dims_i - vec2<i32>(1));
        edl_sum += max(0.0, log(n / (f - textureLoad(depth_texture, edl_nc, 0) * (f - n))) - log_ldc);
        edl_nc = clamp(depth_coord + vec2<i32>(      0,  edl_r), vec2<i32>(0), dims_i - vec2<i32>(1));
        edl_sum += max(0.0, log(n / (f - textureLoad(depth_texture, edl_nc, 0) * (f - n))) - log_ldc);
        edl_nc = clamp(depth_coord + vec2<i32>(-edl_r,  edl_r), vec2<i32>(0), dims_i - vec2<i32>(1));
        edl_sum += max(0.0, log(n / (f - textureLoad(depth_texture, edl_nc, 0) * (f - n))) - log_ldc);
        edl_nc = clamp(depth_coord + vec2<i32>(-edl_r,      0), vec2<i32>(0), dims_i - vec2<i32>(1));
        edl_sum += max(0.0, log(n / (f - textureLoad(depth_texture, edl_nc, 0) * (f - n))) - log_ldc);
        edl_nc = clamp(depth_coord + vec2<i32>(-edl_r, -edl_r), vec2<i32>(0), dims_i - vec2<i32>(1));
        edl_sum += max(0.0, log(n / (f - textureLoad(depth_texture, edl_nc, 0) * (f - n))) - log_ldc);
        edl_nc = clamp(depth_coord + vec2<i32>(      0, -edl_r), vec2<i32>(0), dims_i - vec2<i32>(1));
        edl_sum += max(0.0, log(n / (f - textureLoad(depth_texture, edl_nc, 0) * (f - n))) - log_ldc);
        edl_nc = clamp(depth_coord + vec2<i32>( edl_r, -edl_r), vec2<i32>(0), dims_i - vec2<i32>(1));
        edl_sum += max(0.0, log(n / (f - textureLoad(depth_texture, edl_nc, 0) * (f - n))) - log_ldc);
        // Normalize by sample count then apply exponential response so strength=1
        // gives moderate edge darkening and strength=5 gives near-complete darkening.
        let edl_factor = 1.0 - exp(-params.edl_strength * edl_sum / 8.0);
        colour = colour * (1.0 - edl_factor);
    }

    // Surface LIC: modulate colour by LIC intensity (0.5 = neutral, no change).
    if params.lic_enabled != 0u {
        let lic_val = textureSample(lic_texture, hdr_sampler, in.uv).r;
        let lic_factor = 1.0 + params.lic_strength * (lic_val * 2.0 - 1.0);
        colour = colour * max(0.0, lic_factor);
    }

    // Pre-tone-mapping exposure.
    colour = colour * params.exposure;

    // Tone mapping.
    if params.mode == 0u {
        colour = reinhard(colour);
    } else if params.mode == 1u {
        colour = aces(colour);
    } else {
        colour = khronos_neutral(colour);
    }

    return vec4<f32>(colour, 1.0);
}