react-three-flex
Placing content in threejs is hard.
react-three-flex
brings the web flexbox spec to react-three-fiber.
It is based on yoga, Facebook's open source layout engine for react-native.
Think of how you would normally go about making content responsive, stick to the sides, wrap around, grids, rows, columns, padding, margin. Especially if you are working on frontend-centric projects where the camera is pointing down, forming a 2-dimensional view.
npm install react-three-flex
These demos are real, you can click them! They contain the full code, too.
Table of contents
Usage
You simply create layouts by wrapping your 3D objects in different <Box />
instances inside a <Flex />
container. This way they will be automatically placed in the 3D space following the flexbox specification, just like in the DOM.
import Flex Box from 'react-three-flex' const Layout = <Flex ="center" ="center"> <Box > <mesh = /> </Box> <Box => <mesh = /> </Box> <Box > <mesh = /> </Box> </Flex>
You can tweak the container and the boxes using standard CSS flex properties, like flexDirection
or justifyContent
for the container and flexGrow
for the boxes. There are also shorthands, like align
and justify
. See props docs below for more info.
Anchors
When positioning items, react-three-flex
needs to know where the object anchor is: Yoga Layout expects the object position to be relative to the upper left corner, same as the DOM.
Most THREE.js geometries, though, are positioned relative to the object center. To tell react-three-flex
that your <Box />
positioning is relative to the center you need to set the centerAnchor
prop to true.
<Box > <mesh = /></Box>
If you nest <Box />
elements, though, you need to set it to false. See Nesting.
Stretching
By default react-three-flex
controls elements position only. In some cases you may want to control element sizing too. Since react-three-flex
has no information about how the inner content size works, you need to set your content size manually. To do so react-three-flex
provides you the container size in two ways:
- By using a children render function:
<Flex> <Box ="auto" ="auto" = > width height <Plane = /> </Box></Flex>
- By using an hook:
{ const width height = return <Plane = />} { return <Flex> <Box ="auto" ="auto" = > <Inner /> </Box> </Flex> }
Remember that the useFlexSize
hook works ONLY if your <Box/>
is outside the component.
Invalidation and Reflow
While DOM's Flexbox has full control over all the changes of the tree, react-three-flex
runs on React, hence it has no way to know if a children size or shape has changed. For performance reasons Flex layout calculation does not run every frame, and it has to be triggered manually in some cases.
What will trigger a reflow:
<Flexbox/>
props changes (alignItems, size, ...)<Box/>
props changes (flexGrow, margin, ...)<Flexbox/>
and<Box/>
rerenders with children differences
{ // Since <Box/> is inside the component, setting the state will rerender it, thus causing a reflow. // ⚠️ If <Box/> were outside this component, this would NOT cause a reflow! const state setState = return <Box > <mesh> <boxBufferGeometry ="geometry" = /> </mesh> </Box> }
This will NOT cause a reflow!
{ // ⚠️ Setting state does not rerender <Box/> since it's in the parent // ‼️ No Reflow!! const state setState = return <mesh> <boxBufferGeometry ="geometry" = /> </mesh> } { return <Flex> <Box > <AnimatedBox /> </Box> </Flex> }
For every other cases (setting size with an useFrame
, react-spring animations, <Box/>
not rerendered) you'll need to manually cause a reflow, using useReflow()
hook. Reflows requests are batched every frame, so you can call it from hundreds of components without performance issues.
Animation with useFrame():
{ const ref = const reflow = return <Box > <mesh => <boxBufferGeometry ="geometry" = /> </mesh> </Box> }
<Box/>
outside of component:
{ const state setState = const reflow = return <mesh => <boxBufferGeometry ="geometry" = /> </mesh> }
Sizing
react-three-flex
differs from DOM Flexbox in that it rely on a parent container for the root flex. It is required to specify its dimensions using size
prop for wrapping and to be responsive.
<Flex ="row" ="wrap" => <Box > <mesh = /> </Box> <Box > <mesh = /> </Box> <Box > <mesh = /> </Box></Flex>
⚠️ WATCH OUT! Yoga flexbox engine uses integer numbers to perform layout calculation, so to preserve precision react-three-flex
multiplies every element size and flex prop by the scaleFactor
of the root flex container. By default it's 100
, and works well for small scenes. If you use a different scene scale, make sure to tweak it accordingly.
Axis Orientation
Another important difference with DOM Flexbox is that you have to specify the plane of the container in 3D. The elements will be positioned in the 2D plane given by the two axes, using width and height calculated along the two axes.
The 2D flex container width and height will be calculated by looking at the size
prop with respect of the chosen axes (100 for xy and 200 for y in this example).
The default plane is xy
, the other possibilites are yz
and xz
.
<Flex ="xy" => /* ... */</Flex>
Margin and Padding
For every <Flex />
and <Box />
component you can specify the margin and padding like in DOM elements.
<Flex ="row" = = => <Box = = > <mesh = /> </Box> <Box = = > <mesh = /> </Box></Flex>
Nesting
Since a <Flex />
component works the same way as a DOM one, you can easily make complex layouts by nesting flex containers.
<Flex ="row" ="wrap" => <Box > <mesh = /> </Box> <Box ="column" ="no-wrap"> <Box > <mesh = /> </Box> <Box > <mesh = /> </Box> </Box></Flex>
Measuring the container
When building responsive layouts, you might need to syncronize the size of the 3D Flex container with the DOM, for example, to syncronize scroll position or the height of a scroll container.
To make it easier, you can use the onReflow
callback on the root <Flex>
component, that will be called every time the flex layout is recalculated - e.g. when any content changes.
<Flex => ...</Flex>
API
<Flex = // , = // - ="ltr" // - ="xy" // - , = // - , () = // // , > <Box>/* ... */</Box></Flex>
<Box // , () // , > <mesh = /></Box>
Or you can pass a function as children:
<Box>width height <Model = = /></Box>
Flexbox props
Both <Flex/>
and <Box />
components shares the same Flexbox props API from Yoga. The library also provides string and number inputs for convenience and shorthands.
Example:
// Flex with padding top set to 10, alignItems to 'center', justifyContent to 'space-around' and flexWrap to 'wrap'<Flex = ="center" ="space-around" ="wrap"> <Box /></Flex>
You can find a full list of props inside R3FlexProps
type.