lol/doc/tutorial/12_distance.lolfx

[vert.glsl]

#version 130

in vec2 in_position;

out vec2 pass_position;

void main()
{
    pass_position = in_position;
    gl_Position = vec4(in_position, 0.0, 1.0);
}

[frag.glsl]

#version 130

#if defined GL_ES
precision highp float;
#endif

in vec2 pass_position;

uniform sampler2D u_texture;
uniform float u_flag;
uniform vec3 u_point;
uniform vec3 u_color;

void main(void)
{
    if (u_flag == 0.0)
    {
        float tc = 0.0, ta = 0.0;
        {
            float s = 3.0 + 2.0 * u_point.z;
            vec2 p = pass_position - u_point.xy * 0.9;
            float t = clamp(1.2 - dot(s * p, s * p), 0.0, 1.0);
            float u = t * t * t * t;
            tc += 3.0 * t * t - 2.0 * t * t * t;
            ta += 3.0 * u * u - 2.0 * u * u * u;
        }

        gl_FragColor = vec4(tc * u_color, ta + 0.1);
    }
    else
    {
        vec2 texcoords = pass_position * 0.5 + vec2(0.5, 0.5);
        gl_FragColor = vec4(texture2D(u_texture, texcoords).xyz, 1.0);
    }
}