Hide transparent mesh background?

4.2 godot shaders

Hey is there a quick conditional for vertex to not draw if its not on viewport before setting its alpha? Or what would be the way to hide meshes background so that its seethrough but can’t see its other vertices other than frontside?

I have here a transparent torusmesh:

And this is the shader currently:

shader_type spatial;

void vertex() {
vec4 eyeQuestionmark = vec4(VERTEX, 1.0);
vec4 clip_position = PROJECTION_MATRIX * (MODELVIEW_MATRIX * eyeQuestionmark);
vec3 clip_normal = mat3(PROJECTION_MATRIX) * (mat3(MODELVIEW_MATRIX) * NORMAL);
clip_position.xy += (NORMAL.xy * sin(TIME)*0.03);
POSITION = clip_position;

void fragment() {
ALPHA = 0.4;

So it has a movement shader for the mesh which can be ignored, basically only the fragment() is relevant here. It makes the mesh transparent but also shows all the details for the whole mesh, which I seek to remove.