This post has a short demo showing how a custom shader can be implemented in R3F.

Learning Shaders with Interactive Controls

I am finding shaders to be quite intimidating to learn about. Here's a quick demo and some notes about shaders.

import React, { useRef, useMemo } from 'react';
import { Canvas, useFrame } from '@react-three/fiber';
import { OrbitControls, Sky } from '@react-three/drei';
import { useControls } from 'leva';
import * as THREE from 'three';

function ShaderMesh() {
  const meshRef = useRef();

  const { thresholdX, thresholdY, displacement, baseColor, highlightColor, wireframe, transparent, autoRotate
  } = useControls({
    thresholdX: { value: 0.5, min: 0, max: 1, step: 0.01 },
    thresholdY: { value: 0.5, min: 0, max: 1, step: 0.01 },
    displacement: { value: 0.1, min: 0, max: 1, step: 0.01 },
    baseColor: '#d8d5d5',
    highlightColor: '#00ff00',
    wireframe: true,
    transparent: true,
    autoRotate: false
  });

  const material = useMemo(() => {
    return new THREE.ShaderMaterial({
      vertexShader: `
        uniform float uThresholdX;
        uniform float uThresholdY;
        uniform float uDisplacement;
        varying vec2 vUv; 
        
        void main() {
          vec3 newPosition = position;
          
          if (uv.x > uThresholdX && uv.y > uThresholdY) {
            newPosition.z += uDisplacement;
          }
        
          gl_Position = projectionMatrix * modelViewMatrix * vec4(newPosition, 1.0);
          vUv = uv;
        }
      `,
      fragmentShader: `
        uniform float uThresholdX;
        uniform float uThresholdY;
        uniform vec3 uBaseColor;
        uniform vec3 uHighlightColor;
        varying vec2 vUv; 
      
        void main() {
          vec3 color = uBaseColor;
          
          if (vUv.x > uThresholdX && vUv.y > uThresholdY) {
            color = uHighlightColor;
          }
        
          gl_FragColor = vec4(color, 1.0);
        }
      `,
      uniforms: {
        uThresholdX: { value: thresholdX },
        uThresholdY: { value: thresholdY },
        uDisplacement: { value: displacement },
        uBaseColor: { value: new THREE.Color(baseColor) },
        uHighlightColor: { value: new THREE.Color(highlightColor) }
      },
      side: THREE.DoubleSide,
      wireframe,
      transparent
    });
  }, [thresholdX, thresholdY, displacement, baseColor, highlightColor, wireframe, transparent]);

  useFrame((state) => {
    if (meshRef.current && autoRotate) {
      meshRef.current.rotation.x = state.clock.elapsedTime * 0.3;
      meshRef.current.rotation.y = state.clock.elapsedTime * 0.2;
    }

    // Update uniforms
    if (material.uniforms) {
      material.uniforms.uThresholdX.value = thresholdX;
      material.uniforms.uThresholdY.value = thresholdY;
      material.uniforms.uDisplacement.value = displacement;
      material.uniforms.uBaseColor.value.set(baseColor);
      material.uniforms.uHighlightColor.value.set(highlightColor);
    }
  });

  return (
    <mesh ref={meshRef} material={material}>
      <planeGeometry args={[3, 3, 32, 32]} />
    </mesh>
  );
}

function Scene() {
  return (
    <Canvas camera={{ position: [0, 0, 4], fov: 50 }} style={{ height: '90vh' }}>
      <ambientLight intensity={0.5} />
      <pointLight position={[10, 10, 10]} />
      <Sky sunPosition={[0, 1, 0]} />
      <OrbitControls enableDamping dampingFactor={0.05} />
      <ShaderMesh />
    </Canvas>
  );
}

export default function App() {
  return (
    <div className="w-full h-screen bg-gray-900 relative">
      <Scene />
      <div className="absolute top-4 left-4 text-white">
        <h1 className="text-xl font-bold mb-2">Interactive Shader Demo</h1>
      </div>
    </div>
  );
}

Open Sandbox

What It Shows

The shader demonstrates two core concepts:

Vertex displacement: Push vertices forward based on their UV coordinates. The uThresholdX and uThresholdY uniforms control where this happens.

Fragment coloring: Color pixels differently in the same UV region using the same threshold values.

Learning Through Interaction

Drag the displacement control to see .

The Leva controls expose the key parameters:

Threshold values (where effects trigger)
Displacement amount (how much vertices move)
Colors (base and highlight)
Material properties (wireframe, transparency)

Why This Helps

When you can immediately see how parameters affect the output, shader concepts click faster. You understand the relationship between UV coordinates and effects. You see how vertex and fragment shaders work together.

It's the difference between reading about shaders and actually playing with them.

Next Steps

Once you understand these basics, you can apply the same patterns to more complex effects. The interactive approach works for any shader - just expose the key parameters as uniforms and hook them up to controls.

Start simple, experiment freely, and build up your shader intuition.

Simple Shader Demo

Learning Shaders with Interactive Controls

What It Shows

Learning Through Interaction

Why This Helps

Next Steps

Jeremy Atkinson

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