illumination.fs

uniform sampler2D src_tex_unit0;
uniform vec4 globalColor = vec4(1.0);

in vec2 texCoordVarying;
in vec4 colorVarying;
                                                                  
out vec4 fragColor;

uniform vec3 lightCenter;
uniform float lightRadius;
uniform vec3 lightColor;
uniform float lightCutoff;

uniform sampler2D tex;

vec3 directIllumination(vec3 position, vec3 normal, vec3 center, float rad, vec3 color, float cutoff)
{
    // calculate normalized light vector and distance to sphere light surface
    float r = rad;
    vec3 L = center - position;
    float distance = length(L);
    float d = max(distance - r, 0.);
    L /= distance;
     
    // calculate basic attenuation
    float denom = d/r + 1.;
    float attenuation = 1. / (denom*denom);
     
    // scale and bias attenuation such that:
    //   attenuation == 0 at extent of max influence
    //   attenuation == 1 when d == 0
    attenuation = (attenuation - cutoff) / (1. - cutoff);
    attenuation = max(attenuation, 0.);
     
    float dot = max(dot(L, normal), 0.);
    return color * dot * attenuation;
}


void main()
{
    // if you need a texture, otherwise
  gl_FragColor = vec4(directIllumination(pp, nn, lightCenter, lightRadius, lightColor, lightCutoff).xyz, 1.0) + texture(src_tex_unit0, texCoordVarying);
    
    // if you need a color
    //gl_FragColor = vec4(directIllumination(pp, nn, lightCenter, lightRadius, lightColor, lightCutoff).xyz, 1.0) + colorVarying;

    // no texturing
    // gl_FragColor = vec4(directIllumination(pp, nn, lightCenter, lightRadius, lightColor, lightCutoff).xyz, 1.0);

}

illumination.vs

uniform mat4 projectionMatrix;
uniform mat4 modelViewMatrix;
uniform mat4 textureMatrix;
uniform mat4 modelViewProjectionMatrix;

in vec4  position;
in vec4  color;
in vec2  texcoord;

out vec2 texCoordVarying;
out vec4 colorVarying;

void main()
{
    texCoordVarying = texcoord;
    colorVarying = color;
    gl_Position = modelViewProjectionMatrix * position;
}