setStartPositionEdge 设置初始位置 - 屏幕边缘发射区域

setStartPositionEdge

类型: MethodDeclaration

所属类: ParticleElement

定义位置: animation.ts

描述

设置初始位置 - 屏幕边缘发射区域

参数 movementAngle: 初始移动角度(弧度)

参数

参数名	类型	描述	默认值
movementAngle	number	-	-

返回值

类型: void

源代码

位置: 第 2331 行

private setStartPositionEdge(movementAngle: number): void {
    // 计算屏幕边缘的位置(使用上一帧的摄像机)
    const scrollLeft = Camera.scrollLeft
    const scrollTop = Camera.scrollTop
    const scrollRight = Camera.scrollRight
    const scrollBottom = Camera.scrollBottom
    const width = scrollRight - scrollLeft
    const height = scrollBottom - scrollTop
    const weightX = Math.abs(Math.sin(movementAngle) * width)
    const weightY = Math.abs(Math.sin(movementAngle - Math.PI / 2) * height)
    const threshold = weightX / (weightX + weightY)
    const random = Math.random()
    if (random < threshold) {
      // 从屏幕水平位置(上边或下边)生成粒子
      const forward = this.movementSpeedY >= 0
      this.x = scrollLeft + random / threshold * width
      this.y = forward ? scrollTop : scrollBottom
      const vertices = this.getBoundingRectangle()
      this.x -= (vertices[0] + vertices[2]) / 2 - this.x
      this.y -= forward
      ? vertices[3] - this.y
      : vertices[1] - this.y
    } else {
      // 从屏幕垂直位置(左边或右边)生成粒子
      const forward = this.movementSpeedX >= 0
      this.y = scrollTop + (random - threshold) / (1 - threshold) * height
      this.x = forward ? scrollLeft : scrollRight
      const vertices = this.getBoundingRectangle()
      this.y -= (vertices[1] + vertices[3]) / 2 - this.y
      this.x -= forward
      ? vertices[2] - this.x
      : vertices[0] - this.x
    }
  }

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文档生成时间：2025/7/21 20:53:39