viewport-lib 0.14.0

3D viewport rendering library
Documentation 
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// skybox.wgsl : fullscreen equirectangular environment map background.
// Renders a fullscreen triangle, reconstructs world-space ray from inverse VP,
// and samples the equirect skybox texture.

struct Camera {
    view_proj: mat4x4<f32>,
    eye_pos: vec3<f32>,
    _pad: f32,
    forward: vec3<f32>,
    _pad1: f32,
    inv_view_proj: mat4x4<f32>,
};

struct Lights {
    count: u32,
    shadow_bias: f32,
    shadows_enabled: u32,
    _pad: u32,
    sky_colour: vec3<f32>,
    hemisphere_intensity: f32,
    ground_colour: vec3<f32>,
    _pad2: f32,
    // We only need the IBL fields at the end, but must declare the full
    // struct so offsets are correct. Use a flat array for the lights block.
    _lights_block: array<vec4<f32>, 72>,  // 8 lights * 144 bytes / 16 = 72 vec4s
    ibl_enabled: u32,
    ibl_intensity: f32,
    ibl_rotation: f32,
    show_skybox: u32,
};

@group(0) @binding(0) var<uniform> camera: Camera;
@group(0) @binding(3) var<uniform> lights_uniform: Lights;
@group(0) @binding(10) var ibl_sampler: sampler;
@group(0) @binding(11) var skybox_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 {
    // Fullscreen triangle: 3 vertices cover the entire screen.
    let positions = array<vec2<f32>, 3>(
        vec2<f32>(-1.0, -1.0),
        vec2<f32>( 3.0, -1.0),
        vec2<f32>(-1.0,  3.0),
    );
    var out: VertexOutput;
    out.pos = vec4<f32>(positions[vi], 1.0, 1.0);  // depth = 1.0 (far plane)
    out.uv = positions[vi] * 0.5 + 0.5;
    out.uv.y = 1.0 - out.uv.y;  // flip Y for UV
    return out;
}

const PI: f32 = 3.14159265;

@fragment
fn fs_main(in: VertexOutput) -> @location(0) vec4<f32> {
    // Reconstruct clip-space position.
    let ndc = vec4<f32>(in.uv.x * 2.0 - 1.0, (1.0 - in.uv.y) * 2.0 - 1.0, 1.0, 1.0);

    // Unproject to world space.
    let world_pos = camera.inv_view_proj * ndc;
    let dir = normalize(world_pos.xyz / world_pos.w - camera.eye_pos);

    // Apply Y-axis rotation.
    let rotation = lights_uniform.ibl_rotation;
    let s = sin(rotation);
    let c = cos(rotation);
    let d = vec3<f32>(c * dir.x + s * dir.z, dir.y, -s * dir.x + c * dir.z);

    // Convert direction to equirectangular UV.
    let phi = atan2(d.z, d.x);
    let theta = asin(clamp(d.y, -1.0, 1.0));
    let uv = vec2<f32>(0.5 + phi / (2.0 * PI), 0.5 - theta / PI);

    let colour = textureSampleLevel(skybox_texture, ibl_sampler, uv, 0.0).rgb;
    return vec4<f32>(colour * lights_uniform.ibl_intensity, 1.0);
}