How to avoid transparent mesh Overlay render itself

For example,line mesh like this picture.
when it circles back to itself,the color will get greener,and i don’t want that;
i have tried canvastexture to avoid this,but i want to use CustomBlending material to generate this mesh ,so it won’t achieve my goal.

my material:
const material = new LineMaterial({
color: 0x000000,
linewidth: 20,
side: THREE.DoubleSide,
worldUnits: true,
transparent: true,
opacity: 0.1,
blending: THREE.CustomBlending,
blendSrc: THREE.SrcColorFactor,
blendDst: THREE.DstColorFactor,
blendEquation: THREE.AddEquation,