在threejs中使用顶点着色器旋转几何答案

【问题标题】：Rotating a geometry using vertex shader in threejs在threejs中使用顶点着色器旋转几何
【发布时间】：2020-03-10 05:55:26
【问题描述】：

我正在尝试使用顶点着色器旋转一个盒子，但由于我无法弄清楚的原因，它被剪切了，以下是代码，请帮助我。这是小提琴和我的顶点着色器代码

uniform float delta;
void main()
{
    vec4 modelViewPosition = modelViewMatrix * vec4(position, 1.0);
      gl_Position = (projectionMatrix * modelViewPosition);
      float new_x = gl_Position.x*cos(delta) - gl_Position.y*sin(delta);
      float new_y = gl_Position.y*cos(delta) + gl_Position.x*sin(delta);
      gl_Position.x = new_x;
      gl_Position.y = new_y;
}

https://jsfiddle.net/co4vbhye/

【问题讨论】：

标签： three.js rotation glsl vertex-shader

【解决方案1】：

如果视口为矩形，则由投影矩阵补偿。这意味着必须应用于顶点坐标的最后一个变换是投影矩阵：

clip_position = projection * view * model * position

您必须将旋转应用于顶点坐标position。然后通过视图矩阵和投影矩阵转换结果：

uniform float delta;
void main()
{
    vec3 p = position.xyz;
    float new_x = p.x*cos(delta) - p.y*sin(delta);
    float new_y = p.y*cos(delta) + p.x*sin(delta);

    gl_Position = projectionMatrix * modelViewMatrix * vec4(new_x, new_y, p.z, 1.0);
}

此外，设置为投影矩阵的纵横比 (PerspectiveCamera) 必须与视口的纵横比 (canvas) 相匹配：

要么

//RENDERER
renderer = new THREE.WebGLRenderer();
renderer.setSize(window.innerWidth, window.innerHeight);

//CAMERA
camera = new THREE.PerspectiveCamera(75, window.innerWidth / window.innerHeight, 0.01, 10000);

或

//RENDERER
renderer = new THREE.WebGLRenderer();
renderer.setSize(CANVAS_WIDTH, CANVAS_HEIGHT);

//CAMERA
camera = new THREE.PerspectiveCamera(75, CANVAS_WIDTH / CANVAS_HEIGHT, 0.01, 10000);

看例子：

var renderer,
    scene,
    camera,
    container = document.getElementById('Canvas_3');

//RENDERER
renderer = new THREE.WebGLRenderer();
//renderer.setClearColor(0xffffff);
renderer.setPixelRatio(window.devicePixelRatio);
renderer.setSize(window.innerWidth, window.innerHeight);
container.appendChild(renderer.domElement);

//CAMERA
camera = new THREE.PerspectiveCamera(75, window.innerWidth / window.innerHeight, 0.01, 10000);

//SCENE
scene = new THREE.Scene();

var customUniforms = {
    delta: {
        value: 0
    }
};
var material = new THREE.ShaderMaterial({
    uniforms: customUniforms,
    vertexShader: document.getElementById('vertexShader').textContent,
    fragmentShader: document.getElementById('fragmentShader').textContent
});

var geometry = new THREE.BoxBufferGeometry(1, 1, 1, 0, 0, 0);
var mesh = new THREE.Mesh(geometry, material);
mesh.position.z = -5;
mesh.position.x = 0;
scene.add(mesh);

window.onresize = function() {
    renderer.setSize(window.innerWidth, window.innerHeight);
    camera.aspect = window.innerWidth / window.innerHeight;
    camera.updateProjectionMatrix();
}

//RENDER LOOP
render();

var delta = 0;

function render() {

    delta += 0.006;
    if (delta > 1.57) delta = 0;

    mesh.material.uniforms.delta.value = delta;

    renderer.render(scene, camera);

    requestAnimationFrame(render);
}

<script src="https://cdnjs.cloudflare.com/ajax/libs/three.js/109/three.min.js"></script>
<div id="Canvas_3"></div>

<script type="x-shader/x-vertex" id="vertexShader">
uniform float delta;
void main()
{
    vec3 p = position.xyz;
    float new_x = p.x*cos(delta) - p.y*sin(delta);
    float new_y = p.y*cos(delta) + p.x*sin(delta);
    
    gl_Position = projectionMatrix * modelViewMatrix * vec4(new_x, new_y, p.z, 1.0);
}
</script>

<script type="x-shader/x-fragment" id="fragmentShader">
uniform float delta;
void main() {
    gl_FragColor = vec4(delta, 0.0, 1.0-delta, 1.0);
}
</script>

【讨论】：

非常感谢 :)