15/shaders/bulb.frag

#version 420 core 

layout(std140, binding = 1) uniform Material
{
    vec3 ka;
    vec3 kd;
    vec3 ks;
    float p;
};

in vec3 pos_local;

layout(std140, binding = 4) uniform gamma
{
    float inv_gamma;
};

out vec4 color;

uniform float angle;
uniform vec3 direction;

void main()
{   
    float cosA = dot(normalize(pos_local), normalize(direction));
    if (degrees(acos(cosA)) <= angle)
        color = vec4(pow(ka, vec3(inv_gamma)), 1);
    else
        discard;
}