WebGL制作动画

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绘制流程

  1. 计算变换后的位置坐标。
  2. 清空画板。
  3. 绘制
  4. 循环 1-3 操作。

代码实现

使用库函数简化数学计算

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const vShaderSource = `
    attribute vec4 a_Position;
    uniform mat4 u_ModelMatrix;
    void main() {
        gl_Position = u_ModelMatrix * a_Position;
    }
`

const fShaderSource = `
    void main() {
        gl_FragColor = vec4(0.0, 1.0, 0.0, 1.0);
    }
`

const main = () => {
  const gl = document.querySelector("#canvas").getContext("webgl")
  if (!initShaders(gl, vShaderSource, fShaderSource)) reutrn

  let n = initVertexBuffers(gl)
  if (n < 0) return

  gl.clearColor(0, 0, 0, 1)

  rotating(gl, n, 360)
}

const rotating = (gl, n, ANGLE_STEP = 30) => {
  let currentAngle = 0
  let modelMatrix = new Matrix4()
  let u_ModelMatrix = gl.getUniformLocation(gl.program, "u_ModelMatrix")

  let tick = function () {
    currentAngle = animate(currentAngle, ANGLE_STEP)
    draw(gl, n, currentAngle, modelMatrix, u_ModelMatrix)
    requestAnimationFrame(tick)
  }
  tick()
}

const draw = (gl, n, currentAngle, modelMatrix, u_ModelMatrix) => {
  modelMatrix.setRotate(currentAngle, 0, 0, 1) // Set rotation matrix.
  // modelMatrix.translate(0.5, 0, 0);
  gl.uniformMatrix4fv(u_ModelMatrix, false, modelMatrix.elements)
  gl.clear(gl.COLOR_BUFFER_BIT) // Clear canvas.
  gl.drawArrays(gl.TRIANGLES, 0, n) // Draw triangle.
}

let g_last = Date.now()

/**
 * Get the new angle.
 * @param currentAngle {number}
 * @param ANGLE_STEP {number}
 * @returns {number}
 */
const animate = (currentAngle, ANGLE_STEP) => {
  let now = Date.now()
  let temp = now - g_last
  g_last = now
  return (currentAngle + (ANGLE_STEP * temp) / 1000) % 360
}