Add webworkers to this code. Make sure they use a shared depth and image buffer, as the depth buffer allows for parallelization without regions.

class Renderer {
        constructor({ width = 256, height = 256, context = null } = {}) {
            this.width = width;
            this.height = height;
            this.context = context;
            if (context) {
                this.imageBuffer = context.createImageData(width, height);
            }
            this.depthBuffer = new Float32Array(width * height).fill(Infinity);
            this.lightDirection = normalize([0, 0, 1]);
        }

        render(scene, camera) {
            const { width, height, context, lightDirection, depthBuffer, imageBuffer } = this;

            if (context) {
                if (imageBuffer) imageBuffer.data.fill(0);
                else this.imageBuffer = context.createImageData(width, height);
                depthBuffer.fill(Infinity);
            }

            const cameraMatrix = camera.cameraMatrix;
            const cameraPosition = camera.position;
            const backfaceCulling = camera.backfaceCullingEnabled;


            const toScreen = (v) => [
                (v[0] / v[3] + 1) * 0.5 * width,
                (v[1] / v[3] + 1) * 0.5 * height,
                v[2] / v[3]
            ];

            for (const mesh of scene.meshes) {
                const {transformMatrix, geometry} = mesh;
                const {vertices, vertexNormals, indices} = geometry;
                const worldVertices = new Array(vertices.length);
                const worldNormals = new Array(vertexNormals.length);
                for (let i = 0; i < vertices.length; i++) {
                    const v = vertices[i];
                    const n = vertexNormals[i];
                    worldVertices[i] = fast4x1mul(transformMatrix, [v[0], v[1], v[2], 1]);
                    worldNormals[i] = normalize(fast4x1mul(transformMatrix, [n[0], n[1], n[2], 0]));
                }
                const viewVertices = new Array(worldVertices.length);
                for (let i = 0; i < worldVertices.length; i++) {
                    viewVertices[i] = fast4x1mul(cameraMatrix, worldVertices[i]);
                }

                for (const triangle of indices) {
                    if (backfaceCulling) {
                        const [wv0, wv1, wv2] = [
                            worldVertices[triangle[0]],
                            worldVertices[triangle[1]],
                            worldVertices[triangle[2]]
                        ];
                        const faceNormal = computeNormal(wv0, wv1, wv2);
                        const camToTri = [
                            wv0[0] - cameraPosition[0],
                            wv0[1] - cameraPosition[1],
                            wv0[2] - cameraPosition[2]
                        ];

                        if (dotProduct(faceNormal, camToTri) <= 0) {
                            continue;
                        }
                    }

                    const [vv0, vv1, vv2] = [
                        viewVertices[triangle[0]],
                        viewVertices[triangle[1]],
                        viewVertices[triangle[2]]
                    ];

                    const [n0, n1, n2] = [
                        worldNormals[triangle[0]],
                        worldNormals[triangle[1]],
                        worldNormals[triangle[2]]
                    ];


                    let triangles = [[vv0, vv1, vv2]];
                    let normalSets = [[n0, n1, n2]];

                    for (const [axis, min, max] of [[0, -1, 1], [1, -1, 1], [2, 0, 1]]) {
                        const newTriangles = [];
                        const newNormals = [];
                        for (let i = 0; i < triangles.length; i++) {
                            const clipped = clipTriangle(triangles[i], normalSets[i], axis, min, max);
                            for (const [clippedVertices, clippedNormals] of clipped) {
                                newTriangles.push(clippedVertices);
                                newNormals.push(clippedNormals);
                            }
                        }
                        triangles = newTriangles;
                        normalSets = newNormals;
                        if (triangles.length === 0) break;
                    }

                    for (let i = 0; i < triangles.length; i++) {
                        const [cV0, cV1, cV2] = triangles[i];
                        const [nV0, nV1, nV2] = normalSets[i];

                        const [vv0, vv1, vv2] = [toScreen(cV0), toScreen(cV1), toScreen(cV2)];

                        const colorV0 = Math.max(0, dotProduct(nV0, lightDirection)) * 255;
                        const colorV1 = Math.max(0, dotProduct(nV1, lightDirection)) * 255;
                        const colorV2 = Math.max(0, dotProduct(nV2, lightDirection)) * 255;

                        this.fillTriangle(vv0, vv1, vv2, colorV0, colorV1, colorV2);
                    }
                }
            }

            context.putImageData(this.imageBuffer, 0, 0);
        }

        fillTriangle(v0, v1, v2, color0, color1, color2) {
            const { width, height, imageBuffer, depthBuffer } = this;
        
            // Combine vertices with their associated colors
            let vertices = [
                { pos: v0, color: color0 },
                { pos: v1, color: color1 },
                { pos: v2, color: color2 },
            ];
        
            // Sort the vertices by y-coordinate ascending (sv0.y <= sv1.y <= sv2.y)
            vertices.sort((a, b) => a.pos[1] - b.pos[1]);
        
            // Unpack the sorted vertices and colors
            const [sv0, sv1, sv2] = vertices.map(v => v.pos);
            const [sc0, sc1, sc2] = vertices.map(v => v.color);
        
            // Precompute the denominator for barycentric coordinates
            const denom = (sv1[1] - sv2[1]) * (sv0[0] - sv2[0]) + (sv2[0] - sv1[0]) * (sv0[1] - sv2[1]);
            if (denom === 0) return; // Degenerate triangle
        
            const invDenom = 1 / denom;
        
            // Determine the bounding box of the triangle
            const yStart = Math.max(0, Math.ceil(sv0[1]));
            const yEnd = Math.min(height - 1, Math.floor(sv2[1]));
        
            // Define the triangle edges for intersection tests
            const edges = [
                { v1: sv0, v2: sv1 },
                { v1: sv1, v2: sv2 },
                { v1: sv2, v2: sv0 }
            ];
        
            for (let y = yStart; y <= yEnd; y++) {
                let xMin = width, xMax = 0;
        
                // Find intersection points of the current scanline with the triangle edges
                for (const edge of edges) {
                    const { v1, v2 } = edge;
                    if (y < Math.min(v1[1], v2[1]) || y > Math.max(v1[1], v2[1])) continue;
        
                    const dy = v2[1] - v1[1];
                    if (dy === 0) continue; // Skip horizontal edges
        
                    const t = (y - v1[1]) / dy;
                    const x = v1[0] + t * (v2[0] - v1[0]);
        
                    xMin = Math.min(xMin, x);
                    xMax = Math.max(xMax, x);
                }
        
                // Clamp the x boundaries to the screen dimensions
                const xStart = Math.max(0, Math.ceil(xMin));
                const xEnd = Math.min(width - 1, Math.floor(xMax));
        
                // Precompute the base index for the current scanline in the buffer
                const baseIndex = y * width;
        
                for (let x = xStart; x <= xEnd; x++) {
                    // Compute barycentric coordinates
                    const w0 = ((sv1[1] - sv2[1]) * (x - sv2[0]) + (sv2[0] - sv1[0]) * (y - sv2[1])) * invDenom;
                    const w1 = ((sv2[1] - sv0[1]) * (x - sv2[0]) + (sv0[0] - sv2[0]) * (y - sv2[1])) * invDenom;
                    const w2 = 1 - w0 - w1;
        
                    // Early rejection if the point is outside the triangle
                    if (w0 < 0 || w1 < 0 || w2 < 0) continue;
        
                    // Depth interpolation (assuming z is at index 2)
                    const zInterpolated = 1 / (w0 / sv0[2] + w1 / sv1[2] + w2 / sv2[2]);
        
                    // Buffer index for depth and color
                    const index = baseIndex + x;
        
                    if (zInterpolated < depthBuffer[index]) {
                        depthBuffer[index] = zInterpolated;
        
                        // Perspective-correct color interpolation
                        const interpolatedColor = (w0 * sc0 + w1 * sc1 + w2 * sc2) / (w0 + w1 + w2);
        
                        const shadedColor = [
                            interpolatedColor,
                            interpolatedColor,
                            interpolatedColor,
                            255
                        ];
        
                        const bufferIndex = index * 4;
                        imageBuffer.data[bufferIndex] = shadedColor[0];
                        imageBuffer.data[bufferIndex + 1] = shadedColor[1];
                        imageBuffer.data[bufferIndex + 2] = shadedColor[2];
                        imageBuffer.data[bufferIndex + 3] = shadedColor[3];
                    }
                }
            }
        }

    }