粒子shader 其实是用shader来写粒子的参数效果，用起来过于复杂，这里只贴一个简单随机向四周扩散的粒子shader代码
shader_type particles;
uniform int trail_dilisor = 1;
float rand4seed(inout uint seed){
int k;
int s = int(seed);
if(s==0){
s = 305420679;
k = s/127773;
s = 16807*(s-k*127773)-2836*k;
}
if(s<0){
s+=2147483674;
seed = uint(s);
}
return float(seed%uint(65535))/65535.0;
}
float rand4seed_balance(inout uint seed){
return rand4seed(seed)*2.-1.;
}
uint hash(uint x){
x = ((x>>uint(16))^x)*uint(73244475);
x = ((x>>uint(16))^x)*uint(73244475);
x = (x>>uint(16))^x;
return x;
}
void vertex(){
uint base_num = NUMBER/uint(trail_dilisor);
uint seed1 = hash(base_num+uint(1)+RANDOM_SEED);
uint seed2 = hash(base_num+uint(2)+RANDOM_SEED);
float ran1 = rand4seed_balance(seed1);
float ran2 = rand4seed_balance(seed2);
// VELOCITY = vec3(100.*ran1,100.*ran2,0.);
VELOCITY.x = 100.*ran1+100.*sin(TIME*ran1);
VELOCITY.y = 100.*ran2+100.*sin(TIME*ran2);
// TRANSFORM = mat4(0.,0.,.5,.5);
}
