feat: add Example effect

.storybook/stories/Example.stories.tsx

@@ -0,0 +1,48 @@
+import React, { memo } from 'react'
+import * as THREE from 'three'
+import type { Meta, StoryObj } from '@storybook/react'
+import { Box, useTexture } from '@react-three/drei'
+
+import { Setup } from '../Setup'
+import { EffectComposer, Example } from '../../src'
+import { BlendFunction } from 'postprocessing'
+
+// More on how to set up stories at: https://storybook.js.org/docs/react/writing-stories/introduction
+const meta = {
+  title: 'Effect/Example',
+  component: Example,
+  decorators: [(Story) => <Setup>{Story()}</Setup>],
+  tags: ['autodocs'],
+  argTypes: {
+    blendFunction: {
+      control: 'select',
+      options: Object.keys(BlendFunction),
+      mapping: Object.keys(BlendFunction).reduce((acc, k) => {
+        acc[k] = BlendFunction[k]
+        return acc
+      }, {}),
+    },
+    opacity: { control: { type: 'range', min: 0, max: 1, step: 0.001 } },
+    color: { control: { type: 'color' } },
+  },
+} satisfies Meta<typeof Example>
+
+export default meta
+type Story = StoryObj<typeof meta>
+
+// More on writing stories with args: https://storybook.js.org/docs/react/writing-stories/args
+export const Primary: Story = {
+  render: ({ color, ...args }) => (
+    <>
+      <Box />
+
+      <EffectComposer>
+        <Example color={color && new THREE.Color(color)} {...args} />
+      </EffectComposer>
+    </>
+  ),
+  args: {
+    blendFunction: BlendFunction.ADD,
+    color: 'red' as unknown as THREE.Color,
+  },
+}

src/effects/Example.tsx

@@ -0,0 +1,77 @@
+import * as THREE from 'three'
+import { useRef } from 'react'
+import { useFrame, useThree } from '@react-three/fiber'
+import { BlendFunction, Effect } from 'postprocessing'
+
+import { wrapEffect } from '../util'
+
+//
+// Effect
+//
+
+const ExampleShader = {
+  fragment: `
+  uniform vec3 color;
+  uniform float time;
+  
+  void mainImage(const in vec4 inputColor, const in vec2 uv, out vec4 outputColor) {
+    outputColor = vec4(color, 0.5 + (cos(time) / 2.0 + 0.5));
+  }
+  `,
+}
+
+type ExampleEffectOptions = {
+  /** The color for this effect */
+  color: THREE.Color
+  /** The blend function of this effect */
+  blendFunction?: BlendFunction
+}
+
+export class ExampleEffect extends Effect {
+  constructor({ color, blendFunction }: ExampleEffectOptions) {
+    super('LensFlareEffect', ExampleShader.fragment, {
+      blendFunction,
+      uniforms: new Map<string, THREE.Uniform>([
+        ['color', new THREE.Uniform(color)],
+        ['time', new THREE.Uniform(0)],
+      ]),
+    })
+  }
+
+  update(_renderer: any, _inputBuffer: any, deltaTime: number) {
+    const time = this.uniforms.get('time')
+    if (time) {
+      time.value += deltaTime
+    }
+  }
+}
+
+//
+// Component
+//
+
+const ExampleWrapped = wrapEffect(ExampleEffect)
+
+type ExampleProps = React.ComponentPropsWithoutRef<typeof ExampleWrapped> & {
+  /** mouse */
+  mouse?: boolean
+}
+
+export const Example = ({ mouse = false, ...props }: ExampleProps) => {
+  const pointer = useThree(({ pointer }) => pointer)
+
+  const ref = useRef<ExampleEffect>(null)
+
+  useFrame(() => {
+    if (!mouse) return
+    if (!ref?.current) return
+
+    const uColor = ref.current.uniforms.get('color')
+    if (!uColor) return
+
+    uColor.value.r = pointer.x / 2.0 + 0.5
+    uColor.value.g = pointer.y / 2.0 + 0.5
+  })
+
+  return <ExampleWrapped ref={ref} {...props} />
+}

src/index.tsx

@@ -12,6 +12,7 @@ export * from './effects/ColorDepth'
 export * from './effects/Depth'
 export * from './effects/DepthOfField'
 export * from './effects/DotScreen'
+export * from './effects/Example'
 export * from './effects/Glitch'
 export * from './effects/GodRays'
 export * from './effects/Grid'