shader 来源于 https://forum.cocos.com/t/topic/73013 帖子中，
效果不错，但是由于需求的变更，现在想动态去除shader特效，恢复默认。无从下手。。。。
取的FluxaySuper特效 源码如下
const renderEngine = cc.renderer.renderEngine;
const renderer = renderEngine.renderer;
let CustomMaterial = require('CustomMaterial');
const shader = {
name: 'FluxaySuper',
params: [
{ name: 'time', type: renderer.PARAM_FLOAT, defaultValue: 0 },
],
start() {
this._start = Date.now();
},
update(sprite, material) {
const now = Date.now();
let time = ((now - this._start) / 1000)
material.setParamValue('time', time);
},
defines:[],
vert: `
uniform mat4 viewProj;
attribute vec3 a_position;
attribute vec2 a_uv0;
varying vec2 uv0;
void main () {
vec4 pos = viewProj * vec4(a_position, 1);
gl_Position = pos;
uv0 = a_uv0;
}`,
frag:
`#define TAU 6.12
#define MAX_ITER 5
uniform sampler2D texture;
uniform vec4 color;
uniform float time;
varying vec2 uv0;
void main()
{
float time = time * .5+5.;
// uv should be the 0-1 uv of texture...
vec2 uv = uv0.xy;//fragCoord.xy / iResolution.xy;
vec2 p = mod(uv*TAU, TAU)-250.0;
vec2 i = vec2(p);
float c = 1.0;
float inten = .0045;
for (int n = 0; n < MAX_ITER; n++)
{
float t = time * (1.0 - (3.5 / float(n+1)));
i = p + vec2(cos(t - i.x) + sin(t + i.y), sin(t - i.y) + cos(1.5*t + i.x));
c += 1.0/length(vec2(p.x / (cos(i.x+t)/inten),p.y / (cos(i.y+t)/inten)));
}
c /= float(MAX_ITER);
c = 1.17-pow(c, 1.4);
vec4 tex = texture2D(texture,uv);
vec3 colour = vec3(pow(abs(c), 20.0));
colour = clamp(colour + vec3(0.0, 0.0, .0), 0.0, tex.a);
// 混合波光
float alpha = c*tex[3];
tex[0] = tex[0] + colour[0]*alpha;
tex[1] = tex[1] + colour[1]*alpha;
tex[2] = tex[2] + colour[2]*alpha;
gl_FragColor = color * tex;
}`,
};
CustomMaterial.addShader(shader);