Cheap attenuation

attenuation.glsl

          float dist = length(lightVector);
          float lightR = (lightPosRadius.w / uViewSize.y);

          if(dist < lightR){
            float attenuation = dist/(1.0 - (dist/lightR) * (dist/lightR));
            attenuation = attenuation / lightR + 1.0;
            attenuation = 1.0 / (attenuation * attenuation);

            if (attenuation > 0.0) {
              // normalize vectors
              float normalPower = max(0.0, dot(normal, -normalize(lightVector.xyz)));
              lightColor += diffuse * 2.0 * lc * normalPower * attenuation;
            }
          }