Record a stroke skin bone error of the skirt

As shown in the figure , The skirt has this kind of problem , My first thought was when animating skirt swing , The back of the skirt is too close to the front , But there is no front through the back , So my first thought was to use point multiplication to judge the angle between the opposite direction of the line of sight and the normal direction , If the included angle is close 90 degree , Before the expansion , Otherwise, no outward expansion .

	float3 normalWS = TransformObjectToWorldNormal(normal);
      float3 positionWS = mul(unity_ObjectToWorld, input.positionOS);
           
      float3 viewDir = normalize((_WorldSpaceCameraPos - positionWS));

      float angleNormalView = dot(normalize(normalWS), normalize(viewDir));

      // View direction and smooth normal direction 
      float isShow = angleNormalView < 0.01 ? 1 : 0;
      isShow =  0;
	  outlineWidth *= isShow;

In fact, this method should be useful if it is tracing and adopting the way of positive outward expansion , The way to expand the back is that the direction of the back normal will not let the expanded surface penetrate the front

But at the end of the experiment, I found , Even if I set the stroke width to 0, He still has such dark spots , Then the back armor on the back has no black spots
Then in order to eliminate the problem of transparency , I also set the back armor to be transparent , There are no black spots on the back armor , Set the skirt to opaque , There are still black spots .
In fact, the skirt was not covered properly , It causes the back of the skirt to penetrate into the front .

Back culling is on by default , The penetrating part cannot be seen , But when using tracing, because it is the back tracing , So the back of it can be seen .