updated line drawing shaders

quad_list.cpp

const char * LineSegmentList::VERTEX_SHADER = R"VERTEXSHADER(#version 410

in vec2 vertex;
in vec2 normal;
in vec4 color;
in float width;


out vec2 normal_g;
out vec4 color_g;
out float width_g;

void main(){
    normal_g = normal / length(normal);
    color_g = color;
    width_g = width;
    gl_Position = vec4(vertex, 0, 1);
}
)VERTEXSHADER";


const char * LineSegmentList::GEOMETRY_SHADER = R"GEOMETRYSHADER(#version 410
layout(lines) in;
in vec2 normal_g[];
in float width_g[];
in vec4 color_g[];

uniform mat4 mvp_matrix;

layout(triangle_strip, max_vertices = 4) out;
out vec2 normal_f;
out float width_f;
out vec4 color_f;
out float intensity;

void main()
{
    width_f = width_g[0];
    color_f = color_g[0];
    float segment_length = length(gl_in[0].gl_Position - gl_in[1].gl_Position);

    normal_f = -normal_g[0];
    intensity = segment_length;
    gl_Position = mvp_matrix * (gl_in[0].gl_Position - vec4(((normal_g[0]/length(normal_g[0])) * width_g[0]), 0, 0));
    EmitVertex();

    normal_f = -normal_g[1];
    intensity = 0;
    gl_Position = mvp_matrix * (gl_in[1].gl_Position - vec4(((normal_g[0]/length(normal_g[0])) * width_g[0]), 0, 0));
    EmitVertex();

    normal_f = normal_g[0];
    intensity = segment_length;
    gl_Position = mvp_matrix * (gl_in[0].gl_Position + vec4(((normal_g[0]/length(normal_g[0])) * width_g[0]), 0, 0));
    EmitVertex();

    normal_f = normal_g[1];
    intensity = 0;
    gl_Position = mvp_matrix * (gl_in[1].gl_Position + vec4(((normal_g[0]/length(normal_g[0])) * width_g[0]), 0, 0));
    EmitVertex();

}
)GEOMETRYSHADER";



const char * LineSegmentList::FRAGMENT_SHADER = R"FRAGSHADER(#version 410
in vec4 color_f;
in vec2 normal_f;
in float width_f;
in float intensity;
uniform float time;
out vec4 fragment_color;


void main() {
    float final_intensity = abs(mod(intensity + time,1) - 0.5);
	fragment_color = vec4(color_f.r * final_intensity,color_f.g*final_intensity ,color_f.b * final_intensity, (width_f-length(normal_f)) / width_f  );
}
)FRAGSHADER";