Currently, I have successfully loaded an STL file into my scene with a single color applied to a phong material.
However, I am eager to find a way to apply two colors to this mesh's material and create a gradient effect along the Z-axis similar to the beautiful example shown here.
I suspect that I may need to work with shaders to achieve this, but my experience with three.js is not advanced enough to tackle this challenge yet.
A straightforward method to create a gradient shader using UV coordinates:
const scene = new THREE.Scene();
const camera = new THREE.PerspectiveCamera(60, 1, 1, 1000);
camera.position.set(13, 25, 38);
camera.lookAt(scene.position);
const renderer = new THREE.WebGLRenderer({
antialias: true
});
const canvas = renderer.domElement;
document.body.appendChild(canvas);
const controls = new THREE.OrbitControls(camera, renderer.domElement);
const geometry = new THREE.CylinderBufferGeometry(2, 5, 20, 32, 1, true);
const material = new THREE.ShaderMaterial({
uniforms: {
color1: {
value: new THREE.Color("red")
},
color2: {
value: new THREE.Color("purple")
}
},
vertexShader: `
varying vec2 vUv;
void main() {
vUv = uv;
gl_Position = projectionMatrix * modelViewMatrix * vec4(position, 1.0);
}
`,
fragmentShader: `
uniform vec3 color1;
uniform vec3 color2;
varying vec2 vUv;
void main() {
gl_FragColor = vec4(mix(color1, color2, vUv.y), 1.0);
}
`,
wireframe: true
});
const mesh = new THREE.Mesh(geometry, material);
scene.add(mesh);
render();
function resize(renderer) {
const canvas = renderer.domElement;
const width = canvas.clientWidth;
const height = canvas.clientHeight;
const needResize = canvas.width !== width || canvas.height !== height;
if (needResize) {
renderer.setSize(width, height, false);
}
return needResize;
}
function render() {
if (resize(renderer)) {
camera.aspect = canvas.clientWidth / canvas.clientHeight;
camera.updateProjectionMatrix();
}
renderer.render(scene, camera);
requestAnimationFrame(render);
}html,
body {
height: 100%;
margin: 0;
overflow: hidden;
}
canvas {
width: 100%;
height: 100%;
display: block;
}<script src="https://cdn.jsdelivr.net/npm/three@0.131.6/build/three.min.js"></script>
<script src="https://cdn.jsdelivr.net/npm/three@0.131.6/examples/js/controls/OrbitControls.js"></script>An alternative gradient shader implementation based on object coordinates:
const scene = new THREE.Scene();
const camera = new THREE.PerspectiveCamera(60, 1, 1, 1000);
camera.position.set(13, 25, 38);
camera.lookAt(scene.position);
const renderer = new THREE.WebGLRenderer({
antialias: true
});
const canvas = renderer.domElement;
document.body.appendChild(canvas);
const controls = new THREE.OrbitControls(camera, renderer.domElement);
const geometry = new THREE.CylinderBufferGeometry(2, 5, 20, 16, 4, true);
geometry.computeBoundingBox();
const material = new THREE.ShaderMaterial({
uniforms: {
color1: {
value: new THREE.Color("red")
},
color2: {
value: new THREE.Color("purple")
},
bboxMin: {
value: geometry.boundingBox.min
},
bboxMax: {
value: geometry.boundingBox.max
}
},
vertexShader: `
uniform vec3 bboxMin;
uniform vec3 bboxMax;
varying vec2 vUv;
void main() {
vUv.y = (position.y - bboxMin.y) / (bboxMax.y - bboxMin.y);
gl_Position = projectionMatrix * modelViewMatrix * vec4(position, 1.0);
}
`,
fragmentShader: `
uniform vec3 color1;
uniform vec3 color2;
varying vec2 vUv;
void main() {
gl_FragColor = vec4(mix(color1, color2, vUv.y), 1.0);
}
`,
wireframe: true
});
// More code goes here...
html,
body {
height: 100%;
margin: 0;
overflow: hidden;
}
canvas {
width: 100%;
height: 100%;
display: block;
}<script src="https://cdn.jsdelivr.net/npm/three@0.131.6/build/three.min.js"></script>
<script src="https://cdn.jsdelivr.net/npm/three@0.131.6/examples/js/controls/OrbitControls.js"></script>If you prefer, you can explore different techniques for creating gradients such as shaders, vertex colors, textures, etc.
If you wish to maintain the functionality of the MeshPhongMaterial, one option is to extend the material.
This topic encompasses various approaches, and for a more detailed exploration, you can refer to this resource.
Within the phong materials shader, there is a specific line that resembles this
vec4 diffuseColor = vec4( diffuse, opacity );
Through studying resources like the book of shaders or other tutorials, you'll discover that blending two colors involves using a normalized factor (ranging from 0 to 1).
This implies that you have the option to modify this line to something along these lines
vec4 diffuseColor = vec4( mix(diffuse, customColor, vec3(customFactor)), opacity);
You can expand the shader in the following manner
const customFactor = { value: 0 }
const customColor = {value: new THREE.Color}
myMaterial.onBeforeCompile = shader=>{
shader.uniforms.customFactor = customFactor
shader.uniforms.customColor = customColor
shader.fragmentShader = `
uniform vec3 customColor;
uniform float customFactor;
${shader.fragmentShader.replace(
vec4 diffuseColor = vec4( diffuse, opacity );
vec4 diffuseColor = vec4( mix(diffuse, customColor, vec3(customFactor)), opacity);
)}
`
Upon adjusting customFactor.value, your object's color should transition from myMaterial.color to customColor.value.
To achieve a gradient effect, swapping out customFactor with a dynamic element is essential. One suggestion is to utilize uvs as proposed by prisoners, which involves simple javascript implementation within the shader. Alternate methods may demand additional shader modifications.
vec4 diffuseColor = vec4( mix(diffuse, customColor, vec3(vUv.y)), opacity);
A potential issue that may arise - if you invoke new PhongMaterial({color}), without specifying any textures, the shader will compile without vUv. To ensure its availability in your shader, you could implement:
myMaterial.defines = {USE_MAP:''}
This action would render the vUv variable accessible. Consequently, all lighting aspects of the phong material would influence the material, while the base color undergoes modification.
To keep your gradient static, simply apply a texture to your material using the .map property. Alternatively, you can link it to the .emissiveMap property if you prefer a glowing effect without light sources.
For a dynamic gradient that always fades in the z-axis regardless of model or camera rotation, a custom shader is necessary. Tutorials on creating custom shaders are essential for this task. Check out this example for guidance on implementing custom shaders in Three.js. Additionally, visit to gain insight into crafting a basic gradient shader.
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