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BLEND_NORMAL,
CULLFACE_NONE,
CameraComponent,
Color,
Entity,
LAYERID_IMMEDIATE,
Mesh,
MeshInstance,
SEMANTIC_POSITION,
SEMANTIC_TEXCOORD0,
Script,
ShaderMaterial,
Vec3,
} from 'playcanvas';
import { computeGroundPlane, yOnPlane } from './groundPlane';
import { distanceToCircleEdge } from './xr-scene-bounds';
export type BoundaryWallGeometryParams = {
center: Vec3;
radius: number;
/** Three world-space points defining the ground the wall stands on. Empty or degenerate falls back to baseY. */
groundPlane: Vec3[];
/** Flat base height used when no usable ground plane is supplied. */
baseY: number;
/** Absolute world Y of the wall's top edge, giving a flat top ring however the ground below tilts. */
topY: number;
/** Target grid cell size in world units. Rounded so cells divide the circumference and height evenly. */
gridSpacing: number;
segments?: number;
};
/**
* Flat-array geometry ready for `Mesh.setPositions` / `Mesh.setUvs` / `Mesh.setIndices`, plus the
* grid cell counts the shader needs to know how far the UVs run.
*/
export type BoundaryWallGeometry = {
positions: number[];
uvs: number[];
indices: number[];
columns: number;
rows: number;
};
/**
* Triangle geometry for an upright cylinder standing on the boundary circle. Each segment is a quad
* (two triangles) spanning from the ground up to `topY`; the base is sampled on the ground plane so
* the wall meets the dashed BoundaryRing exactly, while the top is a flat ring at `topY` — the user
* stands on the rig floor, not on the splat's ground plane, so the top is positioned relative to the
* former and only the base follows the latter.
*
* UVs are emitted in **grid cell units** rather than metres — u runs 0..columns around the
* circumference and v runs 0..rows up the wall — so the shader can draw a line at every whole number
* and have the seam at u = columns line up perfectly with u = 0.
*/
export const boundaryWallMesh = ({
center,
radius,
groundPlane,
baseY,
topY,
gridSpacing,
segments = 96,
}: BoundaryWallGeometryParams): BoundaryWallGeometry => {
if (radius <= 0 || segments <= 0 || gridSpacing <= 0) {
return { positions: [], uvs: [], indices: [], columns: 0, rows: 0 };
}
const plane = computeGroundPlane(groundPlane);
const step = (Math.PI * 2) / segments;
// First pass: the bottom of every column, which the row count and the extent guard both need
// before any vertex can be emitted.
const bottoms = Array.from({ length: segments }, (_, index) => {
const angle = index * step;
const x = center.x + radius * Math.cos(angle);
const z = center.z + radius * Math.sin(angle);
return { x, z, y: plane ? yOnPlane(x, z, plane.normal, plane.point, baseY) : baseY };
});
if (bottoms.some((bottom) => bottom.y >= topY)) {
return { positions: [], uvs: [], indices: [], columns: 0, rows: 0 };
}
// Every column has its own world height once the ground tilts, but v still runs 0..rows uniformly
// for all of them, so a single row count has to stand for the whole wall. Deriving it from the
// average bottom is exact for a flat ground plane (the common case) and keeps the cells square on
// average when the plane is tilted.
const averageBottomY = bottoms.reduce((total, bottom) => total + bottom.y, 0) / bottoms.length;
const columns = Math.max(1, Math.round((Math.PI * 2 * radius) / gridSpacing));
const rows = Math.max(1, Math.round((topY - averageBottomY) / gridSpacing));
const positions: number[] = [];
const uvs: number[] = [];
const indices: number[] = [];
const pushColumn = (index: number) => {
// The closing column (index === segments) reuses column 0's position so the loop shuts exactly,
// while u keeps counting up to `columns` to place the seam.
const { x, z, y } = bottoms[index % segments];
const u = (index / segments) * columns;
positions.push(x, y, z, x, topY, z);
uvs.push(u, 0, u, rows);
};
for (let i = 0; i < segments; i++) {
const base = i * 4;
// Per segment: v0 bottom@a0, v1 top@a0, v2 bottom@a1, v3 top@a1.
pushColumn(i);
pushColumn(i + 1);
indices.push(base, base + 1, base + 3, base, base + 3, base + 2);
}
return { positions, uvs, indices, columns, rows };
};
// GLSL only: @playcanvas/react's Application defaults to deviceTypes [DEVICETYPE_WEBGL2], so the
// WGSL variants the engine's own shaders carry would never be compiled here.
const wallVertexGLSL = /* glsl */ `
attribute vec3 vertex_position;
attribute vec2 aUv0;
uniform mat4 matrix_model;
uniform mat4 matrix_viewProjection;
varying vec2 uv0;
varying vec3 vWorld;
void main(void) {
vec4 world = matrix_model * vec4(vertex_position, 1.0);
vWorld = world.xyz;
uv0 = aUv0;
gl_Position = matrix_viewProjection * world;
}
`;
const wallFragmentGLSL = /* glsl */ `
uniform vec3 uHeadPos;
uniform float uFadeDistance;
uniform float uBlockedFadeScale;
uniform float uBlocked;
uniform float uRows;
uniform vec3 uCalmColor;
uniform vec3 uWarnColor;
uniform float uLineHalfWidth;
varying vec2 uv0;
varying vec3 vWorld;
// Antialiased line mask: 1 at whole-number coordinates, 0 between them.
//
// The line has a solid core uLineHalfWidth cells wide either side of the coordinate, so its
// thickness is fixed in world space and holds up close to the wall. The smoothstep then feathers
// it over exactly one pixel (fwidth), which both antialiases the edge and keeps distant lines
// from aliasing into moire: once a cell shrinks below a pixel the feather swallows the core and
// the grid fades out instead of shimmering.
float gridLine(float coord) {
float w = fwidth(coord);
float d = abs(fract(coord + 0.5) - 0.5);
return 1.0 - smoothstep(uLineHalfWidth, uLineHalfWidth + w, d);
}
void main(void) {
// gridLine takes derivatives, which are undefined in non-uniform control flow, so it has to
// run before any discard.
float grid = max(gridLine(uv0.x), gridLine(uv0.y));
// Distance from this fragment to the head, so only the arc of wall near the user lights up.
float fade = uFadeDistance * mix(1.0, uBlockedFadeScale, uBlocked);
float proximity = 1.0 - clamp(distance(vWorld.xz, uHeadPos.xz) / fade, 0.0, 1.0);
if (proximity <= 0.0) discard;
// Soften the open top edge so the wall does not end in a hard rim.
float topFade = 1.0 - smoothstep(0.6, 1.0, uv0.y / uRows);
float alpha = proximity * topFade * grid;
if (alpha <= 0.0) discard;
gl_FragColor = vec4(mix(uCalmColor, uWarnColor, max(proximity, uBlocked)), alpha);
}
`;
/**
* Structural shape of TfXrNavigation this script depends on, kept local so it does not have to
* import the navigation script. `enabled` is optional because a disabled script (e.g. while edit
* mode is on) stops receiving postUpdate and would otherwise latch a stale clampDistance.
*/
type BoundaryWallNavigation = { clampDistance: number; enabled?: boolean };
/**
* Draws a Quest-guardian-style boundary wall: an upright cylinder on the bounds circle whose grid
* fades in and shifts toward a warning colour as the head approaches, and goes to full intensity
* while XR navigation is actively holding the user back.
*
* center / radius / groundPlane / baseY are set imperatively by the BoundaryWall component (see
* BoundaryWall.tsx for why they are not reactive Script props), which calls `rebuild()` afterwards.
*/
export class BoundaryWallScript extends Script {
static scriptName = 'boundaryWall';
center = new Vec3();
radius = 0;
groundPlane: Vec3[] = [];
/** Flat bottom height used when no usable ground plane is supplied. */
baseY = 0;
/**
* Absolute world Y of the wall's top edge. The default puts it 2.5 m above a rig floor at y = 0,
* which is where the user actually stands - the splat's ground plane can be well below that.
*/
topY = 2.5;
segments = 96;
gridSpacing = 0.5;
/** Grid line thickness in world metres. */
lineWidth = 0.025;
/** Head distance, in world metres, at which the wall starts to appear. */
fadeDistance = 1.5;
/** Multiplier applied to fadeDistance while movement is being clamped. */
blockedFadeScale = 2.5;
calmColor = new Color(0.35, 0.7, 1);
warnColor = new Color(1, 0.45, 0.2);
private _material?: ShaderMaterial;
private _mesh?: Mesh;
private _camera: Entity | null = null;
private _navigation: BoundaryWallNavigation | null = null;
private _headParam = new Float32Array(3);
initialize() {
this._material = new ShaderMaterial({
uniqueName: 'boundary-wall',
vertexGLSL: wallVertexGLSL,
fragmentGLSL: wallFragmentGLSL,
attributes: { vertex_position: SEMANTIC_POSITION, aUv0: SEMANTIC_TEXCOORD0 },
});
this._material.blendType = BLEND_NORMAL;
this._material.cull = CULLFACE_NONE;
this._material.depthWrite = false;
this._material.update();
this._resolveDependencies();
this.rebuild();
this.once('destroy', () => {
this._clearMesh();
this._material?.destroy();
this._material = undefined;
this._camera = null;
this._navigation = null;
});
}
/**
* The camera and the navigation script both live on entities this one does not own. They are
* resolved lazily rather than once, because script initialize order across sibling entities is not
* guaranteed and this entity mounts when an XR session starts.
*/
private _resolveDependencies() {
if (!this._camera) {
this._camera = (this.app.root.findComponent('camera') as CameraComponent | null)?.entity ?? null;
}
if (!this._navigation) {
const rig = this.app.root.findByName('camera-root');
// @ts-expect-error - scripts are added dynamically to the entity
this._navigation = (rig?.script?.tfXrNavigation as BoundaryWallNavigation | undefined) ?? null;
}
}
rebuild() {
this._clearMesh();
const geometry = boundaryWallMesh({
center: this.center,
radius: this.radius,
groundPlane: this.groundPlane,
baseY: this.baseY,
topY: this.topY,
gridSpacing: this.gridSpacing,
segments: this.segments,
});
if (geometry.positions.length === 0 || !this._material) {
return;
}
// The shader measures distance in grid cells, so convert. A cell is gridSpacing across only
// approximately - columns and rows are rounded to whole numbers - but that error is well under
// a line width, so it is not worth carrying the exact cell size through as a second uniform.
this._material.setParameter('uLineHalfWidth', (this.lineWidth / this.gridSpacing) * 0.5);
this._material.setParameter('uFadeDistance', this.fadeDistance);
this._material.setParameter('uBlockedFadeScale', this.blockedFadeScale);
this._material.setParameter('uRows', geometry.rows);
this._material.setParameter('uCalmColor', [this.calmColor.r, this.calmColor.g, this.calmColor.b]);
this._material.setParameter('uWarnColor', [this.warnColor.r, this.warnColor.g, this.warnColor.b]);
this._material.setParameter('uBlocked', 0);
this._material.setParameter('uHeadPos', [0, 0, 0]);
const mesh = new Mesh(this.app.graphicsDevice);
mesh.setPositions(geometry.positions);
mesh.setUvs(0, geometry.uvs);
mesh.setIndices(geometry.indices);
mesh.update();
this._mesh = mesh;
const meshInstance = new MeshInstance(mesh, this._material);
if (this.entity.render) {
this.entity.render.meshInstances = [meshInstance];
} else {
// Immediate layer, drawn after the World layer where the splats render, so the wall is not
// composited behind them - same reason BoundaryRingScript uses it.
this.entity.addComponent('render', { meshInstances: [meshInstance], layers: [LAYERID_IMMEDIATE] });
}
}
update() {
this._resolveDependencies();
const material = this._material;
const camera = this._camera;
if (!material || !camera || !this.entity.render) {
return;
}
const navigation = this._navigation;
// A disabled navigation script (e.g. edit mode) stops receiving postUpdate, so its
// clampDistance would otherwise latch whatever value it last held.
const blocked = navigation?.enabled !== false && (navigation?.clampDistance ?? 0) > 0 ? 1 : 0;
const reveal = this.fadeDistance * (blocked ? this.blockedFadeScale : 1);
const head = camera.getPosition();
// Skip the transparent draw entirely while the head is deeper inside than the widest reveal
// radius - every fragment would discard anyway. Toggling render.enabled rather than
// entity.enabled keeps this update running so the wall can come back.
const edgeDistance = distanceToCircleEdge(head.x, head.z, this.center.x, this.center.z, this.radius);
this.entity.render.enabled = this.radius > 0 && edgeDistance > -reveal;
if (!this.entity.render.enabled) {
return;
}
this._headParam[0] = head.x;
this._headParam[1] = head.y;
this._headParam[2] = head.z;
material.setParameter('uHeadPos', this._headParam);
material.setParameter('uBlocked', blocked);
}
private _clearMesh() {
if (this.entity.render) {
this.entity.render.meshInstances = [];
}
if (this._mesh) {
this._mesh.destroy();
this._mesh = undefined;
}
}
}
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