// Glyph (instanced vector field) shader for the 3D viewport.
//
// Group 0: Camera uniform (view-projection, eye position) — same layout as mesh.wgsl.
// + shadow/light uniforms (present in layout, not all used here)
// + ClipPlanes uniform (binding 4).
// Group 1: Glyph uniform (global_scale, scale_by_magnitude, scalar mapping params, ...)
// + LUT texture + sampler.
// Group 2: Per-instance storage buffer
// (GlyphInstance: position vec3, pad, direction vec3, scalar f32).
//
// Vertex input: the glyph base mesh (position vec3, normal vec3 — using Vertex layout
// locations 0 and 1 from the full Vertex struct).
//
// Each instance is oriented so the glyph local +Y axis aligns with the direction vector.
// Scale = global_scale * (optional magnitude scaling).
// Color = LUT(scalar) or LUT(magnitude) depending on has_scalars.
struct Camera {
view_proj: mat4x4<f32>,
eye_pos: vec3<f32>,
_pad: f32,
};
struct ClipPlanes {
planes: array<vec4<f32>, 6>,
count: u32,
_pad0: u32,
viewport_width: f32,
viewport_height: f32,
};
// Glyph uniform — 64 bytes.
struct GlyphUniform {
global_scale: f32, // 4 bytes
scale_by_magnitude: u32, // 4 bytes (1 = scale with magnitude)
has_scalars: u32, // 4 bytes (1 = use per-instance scalar field)
scalar_min: f32, // 4 bytes
scalar_max: f32, // 4 bytes
mag_clamp_min: f32, // 4 bytes
mag_clamp_max: f32, // 4 bytes
has_mag_clamp: u32, // 4 bytes (1 = clamp magnitude to [min, max])
_pad: array<vec4<f32>, 3>, // 48 bytes padding — total 80 bytes
};
// Per-instance data — 32 bytes.
struct GlyphInstance {
position: vec3<f32>, // 12 bytes
_pad0: f32, // 4 bytes
direction: vec3<f32>, // 12 bytes
scalar: f32, // 4 bytes
};
struct ClipVolumeUB {
volume_type: u32,
_pad0: u32, _pad1: u32, _pad2: u32,
plane_normal: vec3<f32>,
plane_dist: f32,
box_center: vec3<f32>,
_padB0: f32,
box_half_extents: vec3<f32>,
_padB1: f32,
box_col0: vec3<f32>,
_padB2: f32,
box_col1: vec3<f32>,
_padB3: f32,
box_col2: vec3<f32>,
_padB4: f32,
sphere_center: vec3<f32>,
sphere_radius: f32,
};
@group(0) @binding(0) var<uniform> camera: Camera;
@group(0) @binding(4) var<uniform> clip_planes: ClipPlanes;
@group(0) @binding(6) var<uniform> clip_volume: ClipVolumeUB;
fn clip_volume_test(p: vec3<f32>) -> bool {
if clip_volume.volume_type == 0u { return true; }
if clip_volume.volume_type == 1u {
return dot(p, clip_volume.plane_normal) + clip_volume.plane_dist >= 0.0;
}
if clip_volume.volume_type == 2u {
let d = p - clip_volume.box_center;
let local = vec3<f32>(
dot(d, clip_volume.box_col0),
dot(d, clip_volume.box_col1),
dot(d, clip_volume.box_col2),
);
return abs(local.x) <= clip_volume.box_half_extents.x
&& abs(local.y) <= clip_volume.box_half_extents.y
&& abs(local.z) <= clip_volume.box_half_extents.z;
}
let ds = p - clip_volume.sphere_center;
return dot(ds, ds) <= clip_volume.sphere_radius * clip_volume.sphere_radius;
}
@group(1) @binding(0) var<uniform> glyph_uniform: GlyphUniform;
@group(1) @binding(1) var lut_texture: texture_2d<f32>;
@group(1) @binding(2) var lut_sampler: sampler;
@group(2) @binding(0) var<storage, read> instances: array<GlyphInstance>;
struct VertexIn {
// Glyph base mesh uses the full Vertex layout (64 bytes stride).
// We only use position (location 0) and normal (location 1).
@location(0) position: vec3<f32>,
@location(1) normal: vec3<f32>,
@location(2) color: vec4<f32>, // unused — here to match buffer stride
@location(3) uv: vec2<f32>, // unused
@location(4) tangent: vec4<f32>, // unused
@builtin(instance_index) instance_index: u32,
};
struct VertexOut {
@builtin(position) clip_pos: vec4<f32>,
@location(0) color: vec4<f32>,
@location(1) world_pos: vec3<f32>,
@location(2) world_nrm: vec3<f32>,
};
// Build a rotation matrix that rotates local +Y to align with `dir`.
// Returns a mat3x3<f32>.
fn rotation_to_align_y(dir: vec3<f32>) -> mat3x3<f32> {
let up = normalize(dir);
// Choose a reference vector not parallel to up.
var ref_v: vec3<f32>;
if abs(up.y) < 0.99 {
ref_v = vec3<f32>(0.0, 1.0, 0.0);
} else {
ref_v = vec3<f32>(1.0, 0.0, 0.0);
}
let right = normalize(cross(ref_v, up));
let fwd = cross(up, right);
return mat3x3<f32>(right, up, fwd);
}
@vertex
fn vs_main(in: VertexIn) -> VertexOut {
var out: VertexOut;
let inst = instances[in.instance_index];
let dir = inst.direction;
let mag = length(dir);
// Compute scale from magnitude.
// When scale_by_magnitude is enabled, normalize magnitude to [0, 1] range
// using the clamp bounds so arrows scale proportionally rather than by raw
// magnitude (which can produce enormous arrows for large velocity fields).
var eff_mag = mag;
if glyph_uniform.has_mag_clamp != 0u {
eff_mag = clamp(eff_mag, glyph_uniform.mag_clamp_min, glyph_uniform.mag_clamp_max);
}
var scale = glyph_uniform.global_scale;
if glyph_uniform.scale_by_magnitude != 0u && mag > 0.0 {
let range = glyph_uniform.mag_clamp_max - glyph_uniform.mag_clamp_min;
if range > 0.0 {
// Normalize to [0, 1] so largest arrow = global_scale, smallest ≈ 0.
let t = (eff_mag - glyph_uniform.mag_clamp_min) / range;
scale = scale * clamp(t, 0.05, 1.0);
}
// If range == 0 (all same magnitude), just use global_scale unchanged.
}
// Build instance transform.
var rot = mat3x3<f32>(
vec3<f32>(1.0, 0.0, 0.0),
vec3<f32>(0.0, 1.0, 0.0),
vec3<f32>(0.0, 0.0, 1.0),
);
if mag > 0.0001 {
rot = rotation_to_align_y(dir / mag);
}
let local_pos = rot * (in.position * scale);
let world_pos = local_pos + inst.position;
let world_nrm = normalize(rot * in.normal);
out.clip_pos = camera.view_proj * vec4<f32>(world_pos, 1.0);
out.world_pos = world_pos;
out.world_nrm = world_nrm;
// Determine color.
if glyph_uniform.has_scalars != 0u {
let raw = inst.scalar;
let range = glyph_uniform.scalar_max - glyph_uniform.scalar_min;
let t = select(0.0, (raw - glyph_uniform.scalar_min) / range, range > 0.0);
let u = clamp(t, 0.0, 1.0);
out.color = textureSampleLevel(lut_texture, lut_sampler, vec2<f32>(u, 0.5), 0.0);
} else {
// Color by magnitude.
let range = glyph_uniform.scalar_max - glyph_uniform.scalar_min;
let t = select(0.0, (mag - glyph_uniform.scalar_min) / range, range > 0.0);
let u = clamp(t, 0.0, 1.0);
out.color = textureSampleLevel(lut_texture, lut_sampler, vec2<f32>(u, 0.5), 0.0);
}
return out;
}
@fragment
fn fs_main(in: VertexOut) -> @location(0) vec4<f32> {
// Clip-plane culling.
for (var i = 0u; i < clip_planes.count; i = i + 1u) {
let plane = clip_planes.planes[i];
if dot(vec4<f32>(in.world_pos, 1.0), plane) < 0.0 {
discard;
}
}
if !clip_volume_test(in.world_pos) { discard; }
// Simple diffuse lighting with a fixed directional light.
let light_dir = normalize(vec3<f32>(0.3, 1.0, 0.5));
let n_dot_l = max(dot(in.world_nrm, light_dir), 0.0);
let ambient = 0.2;
let diffuse = 0.8 * n_dot_l;
let shading = ambient + diffuse;
return vec4<f32>(in.color.rgb * shading, in.color.a);
}