React-three-fiber is a React renderer for Three.js. It allows us to express Three.js in JSX, and there are also many helper functions available in react-three/drei. However, neither react-three-fiber nor react-three/drei offer an easy-to-use way for gesture interaction in React Native. In this tutorial (probably the first tutorial on the internet) you will learn how to implement gesture control, especially the gesture control for cameras, in react-three-fiber in React Native.
So, the core question is: if react-three-fiber and react-three/drei don't have the ability for gesture control in React Native, then how can we implement it on our own? The answer is quite tricky: we can wrap the <Canvas> component with a <View>. Then we monitor the gestures on the <View> instead of any Three.js components, and lastly, we handle the gestures by changing the status of those Three.js components in response.
To achieve our goal, we will first need to use (react-native-gesture-handler)[https://docs.swmansion.com/react-native-gesture-handler/] which is a very popular touch system in React Native.
Installation command for react-native-gesture-handler:
npm install --save react-native-gesture-handlerHere is a quick start about how to use react-native-gesture-handler: https://docs.swmansion.com/react-native-gesture-handler/docs/quickstart/
To summarize, wrap your <Canvas> within the <GestureDetector>, and simply put your gesture handler as the parameter to the <GestureDetector>. Here is an example:
export default function App() {
const panGesture = Gesture.Pan()
.onUpdate((e) => {
// handle pan gesture when panning
})
.onEnd(() => {
// handle pan gesture when gesture is done
});
const pinchGesture = Gesture.Pinch()
.onUpdate((e) => {
// handle pinch gesture when pinching
})
.onEnd(() => {
// handle pinch gesture when gesture is done
});
// combine gestures together
const composed = Gesture.Race(panGesture, pinchGesture);
return (
<View style={styles.container}>
{/* put GestureDetector outside of Canvas with gesture handler */}
<GestureDetector gesture={composed}>
<Canvas>
{/* your three.js componets */}
</Canvas>
</GestureDetector>
</View>
);
}
You might wanna ask: What if we use other gesture handling package? Will that work? Well, you can try it, but please confirm that the package is built for React Native instead of React Web before you use it. For example, the (@use-gesture)[https://use-gesture.netlify.app/] is a package for React Web and it will not work in mobile apps. It's a very bewildering name, right?
As you might notice, in the official document of react-native-gesture-handler (as well as the quick start), they recommend using react-native-reanimated at the same time. However, it is not our case. React-native-reanimated doesn't NOT work for Three.js. In react-three-fiber's official document, the only animation package mentioned is (react-spring)[https://www.react-spring.dev/]. We are going to use it.
Installation command for react-spring:
npm install three @react-spring/threeA short tutorial about how to use react-spring in react-three-fiber: https://docs.pmnd.rs/react-three-fiber/tutorials/using-with-react-spring
Cool! The next issue we need to deal with is how to combine these two packages with react-three-fiber. Let's build a gestured perspective camera as an example.
To start with, we need to have a custom camera to be able to animate the camera. The animated.perspectiveCamera component is from @react-spring/three.
const Camera = (props) => {
const cameraRef = useRef();
const set = useThree(({ set }) => set);
const size = useThree(({ size }) => size);
useLayoutEffect(() => {
if (cameraRef.current) {
cameraRef.current.aspect = size.width / size.height;
cameraRef.current.updateProjectionMatrix();
}
}, [size, props]);
useLayoutEffect(() => {
set({ camera: cameraRef.current });
}, []);
return (
<animated.perspectiveCamera
ref={cameraRef}
fov={75}
near={0.1}
far={100}
position={props.position}
/>
);
};
Now, if we use this custom in <Canvas>, it will replace the default one.
<Canvas>
<Camera position={position} />
</Canvas>
Next, we need to bind the gesture handlers with the animation on the custom camera. The idea is straightforward: bind the pan gesture to move the camera in the XY plane, and pinch gesture for zoom in and out (changing position Z).
Before having the gestures, we need to have our animation springs first.
const [{ position }, api] = useSpring(() => ({
from: { position: [0, 0, 5] },
to: { position: [0, 0, 10] },
}));
The starting position of the camera is (0, 0, 10). Then let's set the pan gesture. When users are panning, the event can monitor the position translation information as translationX and translationY. What we need to do is just call the spring api to set a new position in terms of the original position (savedPos) and the translation information we knew. We need to set the immediate parameter to true so that the animation will be shown immediately.
let savedPos = [0, 0, 10];
const panGesture = Gesture.Pan()
.onUpdate((e) => {
// console.log(e.translationX, e.translationY);
api.start({
from: { position: savedPos },
to: {
position: [
savedPos[0] - e.translationX / 100,
savedPos[1] + e.translationY / 100,
savedPos[2],
],
},
immediate: true,
});
})
.onEnd(() => {
savedPos = position.goal;
});
As for the pinch gesture, the scale is monitored. When scale is between 0 and 1 we should zoom out, and when scale is greater than 1 we should zoom in.
const pinchGesture = Gesture.Pinch()
.onUpdate((e) => {
console.log(e.scale);
api.start({
from: { position: savedPos },
to: {
position: [
savedPos[0],
savedPos[1],
savedPos[2] - (e.scale - 1) * 5,
],
},
immediate: true,
});
})
.onEnd(() => {
savedPos = position.goal;
});
Combine the two gestures together.
const composed = Gesture.Race(panGesture, pinchGesture);
Lastly, we can pass the composed gesture in our <GestureDetector>.
return (
<GestureDetector gesture={composed}>
<View style={styles.canvasContainer}>
<Canvas>
<Camera position={position} />
</Canvas>
</View>
</GestureDetector>
);
The complete code:
import React, { useRef, useState, useLayoutEffect } from "react";
import { StyleSheet, View } from "react-native";
import { Canvas, useFrame, useThree } from "@react-three/fiber/native";
import {
GestureDetector,
Gesture,
} from "react-native-gesture-handler";
import { animated, useSpring } from "@react-spring/three";
function Box(props) {
const mesh = useRef(null);
const [hovered, setHover] = useState(false);
const [active, setActive] = useState(false);
useFrame((state, delta) => (mesh.current.rotation.x += 0.01));
return (
<mesh
{...props}
ref={mesh}
scale={active ? 1.5 : 1}
onClick={(event) => setActive(!active)}
onPointerOver={(event) => setHover(true)}
onPointerOut={(event) => setHover(false)}
>
<boxGeometry args={[1, 1, 1]} />
<meshStandardMaterial color={hovered ? "hotpink" : "orange"} />
</mesh>
);
}
const Camera = (props) => {
const cameraRef = useRef();
const set = useThree(({ set }) => set);
const size = useThree(({ size }) => size);
useLayoutEffect(() => {
if (cameraRef.current) {
cameraRef.current.aspect = size.width / size.height;
cameraRef.current.updateProjectionMatrix();
}
}, [size, props]);
useLayoutEffect(() => {
set({ camera: cameraRef.current });
}, []);
return (
<animated.perspectiveCamera
ref={cameraRef}
fov={75}
near={0.1}
far={100}
position={props.position}
/>
);
};
export default function App() {
const [{ position }, api] = useSpring(() => ({
from: { position: [0, 0, 5] },
to: { position: [0, 0, 10] },
}));
let savedPos = [0, 0, 10];
const panGesture = Gesture.Pan()
.onUpdate((e) => {
// console.log(e.translationX, e.translationY);
api.start({
from: { position: savedPos },
to: {
position: [
savedPos[0] - e.translationX / 100,
savedPos[1] + e.translationY / 100,
savedPos[2],
],
},
immediate: true,
});
})
.onEnd(() => {
savedPos = position.goal;
});
const pinchGesture = Gesture.Pinch()
.onUpdate((e) => {
console.log(e.scale);
api.start({
from: { position: savedPos },
to: {
position: [
savedPos[0],
savedPos[1],
savedPos[2] - (e.scale - 1) * 5,
],
},
immediate: true,
});
})
.onEnd(() => {
savedPos = position.goal;
});
const composed = Gesture.Race(panGesture, pinchGesture);
return (
<View style={styles.container}>
<GestureDetector gesture={composed}>
<View style={styles.canvasContainer}>
<Canvas>
<Camera position={position} />
<ambientLight />
<pointLight position={[10, 10, 10]} />
<Box position={[-1.2, 0, 0]} />
<Box position={[1.2, 0, 0]} />
</Canvas>
</View>
</GestureDetector>
</View>
);
}
const styles = StyleSheet.create({
container: {
flex: 1,
backgroundColor: "#000",
alignItems: "center",
justifyContent: "center",
},
canvasContainer: {
width: "95%",
height: "85%",
backgroundColor: "#fff",
},
});
The final work is not perfect, because we didn't offer a way to rotate the camera or change the camera's facing direction. However, it is very simple to implement it - just pick another gesture and follow the same way. Try it yourself!
Here is the link of the demo project: