vtk-pure-rs 0.2.0

Pure Rust visualization toolkit — data structures, filters, I/O, rendering
Documentation 
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143

struct SsaoUniforms {
    projection: mat4x4<f32>,
    inv_projection: mat4x4<f32>,
    radius: f32,
    bias: f32,
    intensity: f32,
    num_samples: f32,
    texel_size: vec2<f32>,
    near: f32,
    far: f32,
    samples: array<vec4<f32>, 32>,
};

@group(0) @binding(0)
var<uniform> uniforms: SsaoUniforms;
@group(0) @binding(1)
var depth_tex: texture_depth_2d;
@group(0) @binding(2)
var depth_sampler: sampler;
@group(0) @binding(3)
var ao_tex: texture_2d<f32>;

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

@vertex
fn vs_fullscreen(@builtin(vertex_index) idx: u32) -> VertexOutput {
    var out: VertexOutput;
    let x = f32(i32(idx & 1u)) * 4.0 - 1.0;
    let y = f32(i32(idx >> 1u)) * 4.0 - 1.0;
    out.position = vec4<f32>(x, y, 0.0, 1.0);
    out.uv = vec2<f32>((x + 1.0) * 0.5, (1.0 - y) * 0.5);
    return out;
}

// Reconstruct view-space position from depth and UV
fn view_pos_from_depth(uv: vec2<f32>, depth: f32) -> vec3<f32> {
    let ndc = vec4<f32>(uv * 2.0 - 1.0, depth, 1.0);
    let view = uniforms.inv_projection * ndc;
    return view.xyz / view.w;
}

// Pseudo-random hash for noise (avoid banding)
fn hash(p: vec2<f32>) -> f32 {
    let h = dot(p, vec2<f32>(127.1, 311.7));
    return fract(sin(h) * 43758.5453);
}

// SSAO computation
@fragment
fn fs_ssao(in: VertexOutput) -> @location(0) f32 {
    let depth = textureSample(depth_tex, depth_sampler, in.uv);
    if depth >= 1.0 {
        return 1.0; // background, no occlusion
    }

    let view_pos = view_pos_from_depth(in.uv, depth);

    // Approximate normal from depth derivatives
    let px = view_pos_from_depth(in.uv + vec2<f32>(uniforms.texel_size.x, 0.0),
        textureSample(depth_tex, depth_sampler, in.uv + vec2<f32>(uniforms.texel_size.x, 0.0)));
    let py = view_pos_from_depth(in.uv + vec2<f32>(0.0, uniforms.texel_size.y),
        textureSample(depth_tex, depth_sampler, in.uv + vec2<f32>(0.0, uniforms.texel_size.y)));
    let normal = normalize(cross(px - view_pos, py - view_pos));

    // Random rotation per pixel
    let noise_angle = hash(in.uv * 1000.0) * 6.2831853;
    let cs = cos(noise_angle);
    let sn = sin(noise_angle);

    var occlusion = 0.0;
    let ns = u32(uniforms.num_samples);

    for (var i = 0u; i < ns && i < 32u; i = i + 1u) {
        var s = uniforms.samples[i].xyz;
        // Random rotation around normal
        let rotated = vec3<f32>(
            s.x * cs - s.y * sn,
            s.x * sn + s.y * cs,
            s.z,
        );
        // Align sample to surface normal (hemisphere)
        var sample_vec = rotated;
        if dot(sample_vec, normal) < 0.0 {
            sample_vec = -sample_vec;
        }

        let sample_pos = view_pos + sample_vec * uniforms.radius;

        // Project sample to screen space
        let projected = uniforms.projection * vec4<f32>(sample_pos, 1.0);
        let sample_uv = vec2<f32>(
            projected.x / projected.w * 0.5 + 0.5,
            -projected.y / projected.w * 0.5 + 0.5,
        );

        // Sample depth at projected position
        let sample_depth = textureSample(depth_tex, depth_sampler, sample_uv);
        let sample_view = view_pos_from_depth(sample_uv, sample_depth);

        // Range check + occlusion test
        let range_check = smoothstep(0.0, 1.0, uniforms.radius / abs(view_pos.z - sample_view.z));
        if sample_view.z >= sample_pos.z + uniforms.bias {
            occlusion += range_check;
        }
    }

    occlusion = 1.0 - (occlusion / f32(ns)) * uniforms.intensity;
    return clamp(occlusion, 0.0, 1.0);
}

// Bilateral blur (4x4, depth-aware)
@fragment
fn fs_blur(in: VertexOutput) -> @location(0) f32 {
    let center_depth = textureSample(depth_tex, depth_sampler, in.uv);
    var result = 0.0;
    var total_weight = 0.0;

    for (var y = -2; y <= 2; y = y + 1) {
        for (var x = -2; x <= 2; x = x + 1) {
            let offset = vec2<f32>(f32(x), f32(y)) * uniforms.texel_size;
            let sample_uv = in.uv + offset;
            let ao = textureSample(ao_tex, depth_sampler, sample_uv).r;
            let d = textureSample(depth_tex, depth_sampler, sample_uv);
            // Depth-aware weight: reject samples at different depths
            let depth_diff = abs(d - center_depth);
            let weight = exp(-depth_diff * 1000.0);
            result += ao * weight;
            total_weight += weight;
        }
    }

    return result / max(total_weight, 0.001);
}

// Multiply AO onto color (blend state handles multiplication)
@fragment
fn fs_composite(in: VertexOutput) -> @location(0) vec4<f32> {
    let ao = textureSample(ao_tex, depth_sampler, in.uv).r;
    return vec4<f32>(ao, ao, ao, 1.0);
}