feat: added task4 in r3f

Week-2/Task-4/r3f/src/App.jsx

@@ -1,6 +1,172 @@
 
-export default function App() {
+import { useEffect, useMemo, useRef, useState } from 'react'
+import { Canvas, useFrame, useThree } from '@react-three/fiber'
+import * as THREE from 'three'
+
+const STEPS = [
+    {
+        label: 'Step 1: Group at rest',
+        detail: 'Parent group is centered and children keep their offsets.',
+        cameraPosition: [0, 1.7, 6],
+        lookAt: [0, 0, 0],
+        groupPosition: [0, 0, 0],
+        groupRotation: [0, 0, 0],
+        spinSpeed: 0,
+    },
+    {
+        label: 'Step 2: Parent rotation',
+        detail: 'Only parent rotates; children move together without changing local layout.',
+        cameraPosition: [1.7, 1.8, 5.6],
+        lookAt: [0, 0, 0],
+        groupPosition: [0, 0, 0],
+        groupRotation: [0.15, 0.55, 0],
+        spinSpeed: 0.015,
+    },
+    {
+        label: 'Step 3: Parent move + rotate',
+        detail: 'Parent shifts and rotates as one unit while child spacing stays intact.',
+        cameraPosition: [0.6, 2.4, 7],
+        lookAt: [0.4, 0.35, 0],
+        groupPosition: [0.7, 0.4, -0.4],
+        groupRotation: [0.35, 1.2, 0.2],
+        spinSpeed: 0.03,
+    },
+]
+
+function GuidedGroupScene({ stepIndex }) {
+    const { camera } = useThree()
+    const groupRef = useRef()
+
+    const targets = useMemo(
+        () => ({
+            cameraPosition: new THREE.Vector3(),
+            cameraLookAt: new THREE.Vector3(),
+            lookCurrent: new THREE.Vector3(),
+            groupPosition: new THREE.Vector3(),
+            groupRotation: new THREE.Euler(),
+            spinSpeed: 0,
+            initialized: false,
+        }),
+        []
+    )
+
+    useEffect(() => {
+        const step = STEPS[stepIndex]
+
+        targets.cameraPosition.set(...step.cameraPosition)
+        targets.cameraLookAt.set(...step.lookAt)
+        targets.groupPosition.set(...step.groupPosition)
+        targets.groupRotation.set(...step.groupRotation)
+        targets.spinSpeed = step.spinSpeed
+
+        if (groupRef.current && !targets.initialized) {
+            camera.position.copy(targets.cameraPosition)
+            targets.lookCurrent.copy(targets.cameraLookAt)
+            groupRef.current.position.copy(targets.groupPosition)
+            groupRef.current.rotation.copy(targets.groupRotation)
+            targets.initialized = true
+        }
+    }, [camera, stepIndex, targets])
+
+    useFrame(() => {
+        if (!groupRef.current) return
+
+        groupRef.current.position.lerp(targets.groupPosition, 0.1)
+
+        groupRef.current.rotation.x += (targets.groupRotation.x - groupRef.current.rotation.x) * 0.1
+        groupRef.current.rotation.y += (targets.groupRotation.y - groupRef.current.rotation.y) * 0.1
+        groupRef.current.rotation.z += (targets.groupRotation.z - groupRef.current.rotation.z) * 0.1
+
+        groupRef.current.rotation.y += targets.spinSpeed * 0.2
+
+        camera.position.lerp(targets.cameraPosition, 0.08)
+        targets.lookCurrent.lerp(targets.cameraLookAt, 0.08)
+        camera.lookAt(targets.lookCurrent)
+    })
+
     return (
-        <></>
+        <>
+            <ambientLight intensity={0.8} />
+            <directionalLight intensity={1} position={[4, 5, 4]} />
+
+            <mesh rotation={[-Math.PI / 2, 0, 0]} position={[0, -1.2, 0]}>
+                <planeGeometry args={[12, 12]} />
+                <meshStandardMaterial color="#dde7f3" roughness={0.95} />
+            </mesh>
+
+            <group ref={groupRef}>
+                <mesh position={[-1.1, 0, 0]}>
+                    <boxGeometry args={[0.9, 0.9, 0.9]} />
+                    <meshStandardMaterial color="#2a9d8f" />
+                </mesh>
+
+                <mesh position={[1.1, 0, 0]}>
+                    <sphereGeometry args={[0.55, 24, 24]} />
+                    <meshStandardMaterial color="#e76f51" />
+                </mesh>
+
+                <mesh position={[0, 0.95, 0]}>
+                    <coneGeometry args={[0.42, 0.85, 24]} />
+                    <meshStandardMaterial color="#457b9d" />
+                </mesh>
+            </group>
+        </>
+    )
+}
+
+export default function App() {
+    const [stepIndex, setStepIndex] = useState(0)
+    const step = STEPS[stepIndex]
+
+    useEffect(() => {
+        function onKeyDown(event) {
+            if (event.key === '1') setStepIndex(0)
+            if (event.key === '2') setStepIndex(1)
+            if (event.key === '3') setStepIndex(2)
+        }
+
+        window.addEventListener('keydown', onKeyDown)
+        return () => window.removeEventListener('keydown', onKeyDown)
+    }, [])
+
+    return (
+        <div className="app-shell">
+            <div id="guide">
+                <h2>Task 4: Group Motion</h2>
+                <p id="step-label">{step.label}</p>
+                <p id="step-detail">{step.detail}</p>
+
+                <div className="row">
+                    {STEPS.map((_, index) => (
+                        <button
+                            key={index}
+                            className={`step-btn ${stepIndex === index ? 'active' : ''}`}
+                            onClick={() => setStepIndex(index)}
+                        >
+                            Step {index + 1}
+                        </button>
+                    ))}
+                </div>
+
+                <div className="row">
+                    <button onClick={() => setStepIndex((value) => Math.max(value - 1, 0))} disabled={stepIndex === 0}>
+                        Previous
+                    </button>
+                    <button
+                        onClick={() => setStepIndex((value) => Math.min(value + 1, STEPS.length - 1))}
+                        disabled={stepIndex === STEPS.length - 1}
+                    >
+                        Next
+                    </button>
+                </div>
+
+                <p id="hint">Simple parent group animation. Keys: 1, 2, 3.</p>
+            </div>
+
+            <Canvas camera={{ fov: 55, near: 0.1, far: 100, position: [0, 1.7, 6] }}>
+                <color attach="background" args={['#edf3fa']} />
+                <GuidedGroupScene stepIndex={stepIndex} />
+            </Canvas>
+        </div>
     )
 }

Week-2/Task-4/r3f/src/index.css

@@ -4,5 +4,98 @@ body,
     width: 100%;
     height: 100%;
     margin: 0;
-    background-color: black;
+}
+
+body {
+    overflow: hidden;
+    background: #edf3fa;
+    font-family: "Avenir Next", "Segoe UI", sans-serif;
+}
+
+canvas {
+    display: block;
+    width: 100%;
+    height: 100%;
+}
+
+.app-shell {
+    position: relative;
+    width: 100%;
+    height: 100%;
+}
+
+#guide {
+    position: fixed;
+    top: 14px;
+    left: 14px;
+    z-index: 10;
+    max-width: 300px;
+    background: rgba(255, 255, 255, 0.88);
+    border: 1px solid rgba(0, 0, 0, 0.1);
+    border-radius: 10px;
+    padding: 10px;
+    box-shadow: 0 8px 20px rgba(0, 0, 0, 0.12);
+    display: flex;
+    flex-direction: column;
+    gap: 8px;
+}
+
+#guide h2 {
+    margin: 0;
+    font-size: 14px;
+    color: #203448;
+}
+
+#step-label {
+    margin: 0;
+    font-size: 13px;
+    font-weight: 700;
+    color: #1b2530;
+}
+
+#step-detail {
+    margin: 0;
+    font-size: 12px;
+    color: #4f647a;
+    line-height: 1.35;
+}
+
+.row {
+    display: flex;
+    gap: 6px;
+    flex-wrap: wrap;
+}
+
+button {
+    border: 1px solid #cfd8e3;
+    background: #fff;
+    color: #203448;
+    border-radius: 8px;
+    padding: 7px 9px;
+    font-size: 12px;
+    cursor: pointer;
+    transition: all 0.2s ease;
+}
+
+button:hover {
+    border-color: #8ea2b8;
+    transform: translateY(-1px);
+}
+
+button.step-btn.active {
+    background: #203448;
+    border-color: #203448;
+    color: #f4f8fb;
+}
+
+button:disabled {
+    opacity: 0.5;
+    cursor: not-allowed;
+    transform: none;
+}
+
+#hint {
+    margin: 0;
+    font-size: 11px;
+    color: #566f86;
 }