CocosCreator实现划过的位置显示纹理

1、项目需求

项目需要有一个功能：是当一个光点走过的路径，这个路径的位置就都亮起来的功能。

 

2、资料内容

功能类似这位大神的橡皮擦功能：https://forum.cocos.org/t/2-0-8/74246

但是，项目的需求还要经过的路径周围有模糊的外边——也就是从中心到边缘越来越暗。

所以对于借鉴了网上大神的shader例子，类似以下的示例：

在大神的肩膀上做了一些改动，来实现项目的需求。

 

3、项目示例

以下是我自己的测试项目的示例：

（请忽略这渣渣的画质，懒得装录屏软件了）

 

4、项目代码

 

SliderPointLight.ts

const { ccclass, property } = cc._decorator;

@ccclass
export default class Follow_spot extends cc.Component {
  @property(cc.Node)
  bg: cc.Node = null;
  material: cc.Material = null;
  center: number[] = [0.5, 0.5];
  testArr: number[] = [];

  onLoad() {
    this.material = this.bg.getComponent(cc.Sprite).getMaterial(0);
    this.material.setProperty('wh_ratio', this.bg.width / this.bg.height);
    this.material.setProperty('center', this.center);

    //js 中最重要是这一句,这里参数是数组长度*数组里向量的维度
    this.material.setProperty('colorArr', new Float32Array(400));
    //这里设置的时候需要把数组里向量的分量展开到一个一维数组
    this.material.setProperty('colorArr', []);

    this.bg.on(cc.Node.EventType.TOUCH_MOVE, this.touchMoveEvent, this);
  }

  touchMoveEvent(evt: cc.Event.EventTouch) {
    this.center[0] = evt.getLocation().x / this.bg.width;
    this.center[1] = 1 - evt.getLocation().y / this.bg.height;
    console.log(this.center);
    this.material.setProperty('center', this.center);
    if (this.testArr.length >= 400) {
      this.testArr.shift();
      this.testArr.shift();
    }
    this.testArr.push(this.center[0]);
    this.testArr.push(this.center[1]);


    //js 中最重要是这一句,这里参数是数组长度*数组里向量的维度
    this.material.setProperty('colorArr', new Float32Array(this.testArr));
    //这里设置的时候需要把数组里向量的分量展开到一个一维数组
    this.material.setProperty('colorArr', this.testArr);
  }
}

 

SliderPointLight.effect

CCEffect %{
  techniques:
  - passes:
    - vert: vs
      frag: fs
      blendState:
        targets:
        - blend: true
      rasterizerState:
        cullMode: none
      properties:
        texture: { value: white }
        wh_ratio: {
          value: 1.78,
          editor: {
            tooltip: "宽高比"
          }
        }
        blur: {
          value: 0.35,
          editor: {
            tooltip: "光圈模糊程度"
          }
        }
        radius: {
          value: 0.5,
          editor: {
            tooltip: "光圈半径"
          }
        }
        center: {
          value: [0.5, 0.5],
          editor: {
            tooltip: "光圈起点"
          }
        }
        colorArr: {value: [0.5,0.5,0.5,0.5]}
}%


CCProgram vs %{
  precision highp float;

  #include 
  #include 

  in vec3 a_position;
  in vec4 a_color;
  out vec4 v_color;

  #if USE_TEXTURE
  in vec2 a_uv0;
  out vec2 v_uv0;
  #endif

  void main () {
    vec4 pos = vec4(a_position, 1);

    #if CC_USE_MODEL
    pos = cc_matViewProj * cc_matWorld * pos;
    #else
    pos = cc_matViewProj * pos;
    #endif

    #if USE_TEXTURE
    v_uv0 = a_uv0;
    #endif

    v_color = a_color;

    gl_Position = pos;
  }
}%

CCProgram fs %{

  precision highp float;

  #include 

  in vec4 v_color;

  #if USE_TEXTURE
  in vec2 v_uv0;
  uniform sampler2D texture;
  #endif

  uniform ARGS{
    float radius;
    float blur;
    vec2 center;
    float wh_ratio;
  };

  //effect定义
   uniform Metaball {
       vec4 colorArr[100];
   };

  void main () {
    vec4 o = vec4(1, 1, 1, 0);
    o *= texture(texture, v_uv0);
    o *= v_color;
    float circle = radius * radius;
    for(int i = 0; i < 100; i++) {
      float colorX = colorArr[i].x;
      float colorY = colorArr[i].y;
      float rx = colorX * wh_ratio;
      float ry = colorY;
      float dis = (v_uv0.x * wh_ratio - rx) * (v_uv0.x * wh_ratio - rx) + (v_uv0.y  - ry) * (v_uv0.y - ry);

      o.a = smoothstep(circle, circle - blur, dis)+o.a;
    }

    gl_FragColor = o;
  }
}%