// sending the vertices to gpu:
val a = Vec3(1,0.5f,1)
val b = Vec3(-1,1,-2)

var normal = calcNorm(a,b, cam.pos)

// in shader: (a_position, a_normal, a_color)
vertices.queueVertex(a, -normal, Color.BLUE)
vertices.queueVertex(a, normal, Color.BLUE)
vertices.queueVertex(b, -normal, Color.YELLOW)
vertices.queueVertex(b, normal, Color.YELLOW)


...

// calcNorm function:

    fun calcNorm(a: Vec3, b: Vec3, camPos: Vec3): Vec3 {
        return glm.glm.cross((a-b), (camPos-a)).normalize()
    }

...

// shader for drawing the line:

attribute vec3 a_position;
attribute vec3 a_normal;
attribute vec3 a_color;

uniform mat4 model;
uniform mat4 proj;
uniform mat4 ortho;
uniform mat4 view;
uniform vec3 campos;
varying vec4 v_pos;
varying vec3 v_color;

float linewidth = 0.04;
void main() {
    vec4 pos = view * model * vec4((a_position), 1.0);
    float dist = length(vec4(campos, 0.0) - (model * vec4((a_position), 0.0)));
    vec4 delta = vec4((a_normal * (linewidth*dist)), 0.0);
    gl_Position = proj * (pos + delta);
    v_color = a_color;
    v_pos = pos;
}