CocosCreator如何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

CocosCreator如何实现划过的位置显示纹理

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：

CocosCreator如何实现划过的位置显示纹理

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：

CocosCreator如何实现划过的位置显示纹理

（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 <cc-global>

									        #include <cc-local>

									        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 <alpha-test>

									        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;

									        }

									    }%