How to write a Three-view drawings shader(in Unity3d)?

Question

I attempt implement a Three-view drawings shader for simple geometry and have test with this shader,simple as:

float doCos = dot(viewDirection, normalDirection);
float4 texColor;

//2. need board
bool isBackSide = doCos < 0;

if(isBackSide) {
    //_Dotted is a 2d texture the board is black dot line
    texColor = tex2D(_Dotted, i.tex.xy *  _Dotted_ST.xy + _Dotted_ST.zw);
} else {
    //_Dotted is a 2d texture the board is black entity line
    texColor = tex2D(_Entity, i.tex.xy * _Entity_ST.xy + _Entity_ST.zw);
}

//ignore some color
if(texColor.x > 0.5f) {
    discard;
}

return texColor;

There have a problem the dotted line will obvious then entity line when forward plane become steep.also, I add a rim line but its not point so I ignore it. in order to clarify, I use two questions:
1. how to modify that shader solve dotted line problem?
2. Does have exist professional Three-view drawings shader?(not find yet)