WebGL 绘制与变换使用示例详解

webgl.drawArrays(webgl.POINTS, 0, points.length / 4)

const VSHADER_SOURCE = `
  attribute vec4 a_Position;
  uniform vec4 u_Translate;
  void main() {
     gl_Position = u_Translate + a_Position;
  }
 `
const u_Translate = gl.getUniformLocation(gl.program, 'u_Translate')
gl.uniform4f(u_Translate, 0.5, 0.5, 0.0, 0)

const u_Translate = gl.getUniformLocation(program, 'u_Translate');
// 定义顶点数据 
const positions = [ 0, 0, 0.5, 0, 0.5, 0.5, 0, 0.5, ];
// 将顶点数据写入缓冲区 
gl.bufferData(gl.ARRAY_BUFFER, new Float32Array(positions), gl.STATIC_DRAW);
// 启用属性并指定数据格式 
gl.enableVertexAttribArray(aPosition); 
gl.vertexAttribPointer(aPosition, 2, gl.FLOAT, false, 0, 0);
// 设置平移向量 
const translation = [0.5, 0.5]; // 将平移向量传递给uniform变量 
gl.uniform2fv(translationUniformLocation, translation); // 绘制图形 
gl.drawArrays(gl.TRIANGLE_FAN, 0, positions.length / 2);

const vertexShaderSource = `
  attribute vec2 a_position;
  uniform vec2 u_rotationCenter;
  uniform float u_angle;
  varying vec3 v_color;
  void main() {
    vec2 rotatedPosition = vec2(
      cos(u_angle) * (a_position.x - u_rotationCenter.x) - sin(u_angle) * (a_position.y - u_rotationCenter.y) + u_rotationCenter.x,
      sin(u_angle) * (a_position.x - u_rotationCenter.x) + cos(u_angle) * (a_position.y - u_rotationCenter.y) + u_rotationCenter.y
    );
    gl_Position = vec4(rotatedPosition, 0, 1);
    v_color = vec3(cos(u_angle), 3.14 - cos(u_angle), cos(u_angle));
}
`

const fragmentShaderSource = `
  precision mediump float;
  varying vec3 v_color;
  void main() {
    gl_FragColor = vec4(v_color, 1);
  }
`

// 设置旋转中心和旋转角度
const rotationCenter = [0.25, 0.25];
let angle = 0
function render() {
  // 更新旋转角度
  angle += 0.01
  if (angle === 3.1415926) {
    angle = 0
  }
  // 将旋转中心和旋转角度传递给uniform变量
  webgl.uniform2fv(rotationCenterUniformLocation, rotationCenter)
  webgl.uniform1f(angleUniformLocation, angle)
  draw()
  // 绘制图形
  webgl.drawArrays(webgl.TRIANGLE_FAN, 0, 4);
  // 请求浏览器调用下一帧动画
  requestAnimationFrame(render)
}
// 开始动画
render()

var vertexShaderSource = `
  attribute vec3 aVertexPosition;
  uniform float uScale;
  void main() {
    gl_Position = vec4(aVertexPosition * uScale, 1.0);
  }
`

const scaleUniformLocation = webgl.getUniformLocation(webgl.program, "uScale")
webgl.uniform1f(scaleUniformLocation, scale)

canvas.addEventListener("wheel", function (event: any) {
  scale += event.deltaY / 1000
})