渲染着色器而无需在 ThreeJS 中向场景添加几何体

Question

我目前正在尝试仅使用着色器绘制形状或至少相当于 ThreeJS r128 中的 geometry。

使用此库在屏幕上绘制内容的常用方法包括创建一个 mesh 和一个 geometry（这里是 boilerplate code for project creation) associated to it. After the creation of that object, we can apply a shader to this new component via the ShaderMaterial class。

但是，我找不到如何在场景而不是对象上渲染着色器。使用 OpenGL 着色语言 (GLSL)，我们实际上可以在没有顶点的情况下在屏幕上绘制形状。本来就是这么想的，不过好像被这个渲染系统给纠结了

是否可以仅使用 ThreeJS 中的着色器进行渲染？

为了测试，这里有一个用着色器创建实心圆的函数：

片段着色器：

uniform vec2 u_resolution;

float circleShape(vec2 position, float radius){
    return step(radius, length(position));
}

void main(){
    vec2 position = gl_FragCoord.xy / u_resolution;
    float circle = circleShape(position, 0.3);
    vec3 color = vec3(circle);
    gl_FragColor = vec4(color, 1.0);
}

这是我的顶点着色器以防万一：

void main(){
    gl_Position = projectionMatrix * modelViewMatrix * vec4(position, 1.0);
}

Answer 1

就在整个canvas上画一个THREE.PlaneGeometry:

var container, camera, scene, renderer, uniforms;

init();
animate();

function init() {
    container = document.getElementById( 'container' );
    camera = new THREE.Camera();
    camera.position.z = 1;
    scene = new THREE.Scene();
    var geometry = new THREE.PlaneGeometry( 2, 2 );

    uniforms = {
        //u_time: { type: "f", value: 1.0 },
        u_resolution: { type: "v2", value: new THREE.Vector2() },
        //u_mouse: { type: "v2", value: new THREE.Vector2() }
    };

    var material = new THREE.ShaderMaterial( {
        uniforms: uniforms,
        vertexShader: document.getElementById( 'vertexShader' ).textContent,
        fragmentShader: document.getElementById( 'fragmentShader' ).textContent
    } );

    var mesh = new THREE.Mesh( geometry, material );
    scene.add( mesh );

    renderer = new THREE.WebGLRenderer();
    renderer.setPixelRatio( window.devicePixelRatio );
    container.appendChild( renderer.domElement );
    onWindowResize();
    window.addEventListener( 'resize', onWindowResize, false );
    document.onmousemove = function(e){
        //uniforms.u_mouse.value.x = e.pageX
        //uniforms.u_mouse.value.y = e.pageY
    }
}

function onWindowResize( event ) {
    renderer.setSize( window.innerWidth, window.innerHeight );
    uniforms.u_resolution.value.x = renderer.domElement.width;
    uniforms.u_resolution.value.y = renderer.domElement.height;
}

function animate(delta_ms) {
    requestAnimationFrame(animate);
    render(delta_ms);
}

function render(delta_ms) {
    //uniforms.u_time.value = delta_ms;
    renderer.render( scene, camera );
}

<script src="https://cdn.jsdelivr.net/npm/three@0.128/build/three.js"></script>
<div id="container"></div>

<script id="vertexShader" type="x-shader/x-vertex">
void main() {
    gl_Position = vec4( position, 1.0 );
}
</script>

<script id="fragmentShader" type="x-shader/x-fragment">
precision mediump float;

uniform vec2 u_resolution;

float circleShape(vec2 position, float radius){
    return step(radius, length(position));
}

void main(){
    vec2 position = gl_FragCoord.xy / u_resolution;
    float circle = circleShape(position, 0.3);
    vec3 color = vec3(circle);
    gl_FragColor = vec4(color, 1.0);
} 
</script>

渲染着色器而无需在 ThreeJS 中向场景添加几何体

Render a shader without having to add a Geometry to the scene in ThreeJS

javascript

three.js

glsl

shader

webgl