Specular Light appears on both sides - c++

Question

I have a very strange behaviour of specular(phong light model) light. It seems to be appering on both sides of all objects. Does anyone know what could be the issue ?
The actual calculation seems to be alright, as I can see that the light changes its position as object rotates.
#version 330
in vec4 CameraPos0;
in vec3 Pos0;
in vec4 Colour0;
in vec3 Normal0;
out vec4 FragColor;
// Ambient light parameters
uniform vec3 gAmbientLightIntensity;
// Directional light parameters
uniform vec3 gDirectionalLightIntensity;
uniform vec3 gDirectionalLightDirection;
// Specular light parameter
uniform vec3 gSpecularLightIntensity;
uniform vec3 gLightSourcePosition;
uniform vec3 gCameraPosition;
// Material constants
uniform float gKa;
uniform float gKd;
uniform float gKs;
void main()
{
// Calculate the ambient light intensity at the vertex
// Ia = Ka * ambientLightIntensity
vec4 ambientLightIntensity = gKa * vec4(gAmbientLightIntensity, 1.0);
// Setup the light direction and normalise it
vec3 lightDirection = normalize(-gDirectionalLightDirection);
//lightDirection = normalize(gDirectionalLightDirection);
// Id = kd * lightItensity * N.L
// Calculate N.L
float diffuseFactor = dot(Normal0, lightDirection);
diffuseFactor = clamp(diffuseFactor, 0.0, 1.0);
// N.L * light source colour * intensity
vec4 diffuseLightIntensity = gKd * vec4(gDirectionalLightIntensity, 1.0f) * diffuseFactor;
// Phong light
vec3 L = normalize(gLightSourcePosition - Pos0);
vec3 V = normalize(-Pos0);
vec3 R = normalize(2 * Normal0 * dot(Normal0, L) - L);
float specularFactor = pow(dot(R, V), 0.1f);
vec4 specularLightIntensity = gKs * vec4(gSpecularLightIntensity, 1.0f) * specularFactor;
specularLightIntensity = clamp(specularLightIntensity, 0.0, 1.0);
// Final vertex colour is the product of the vertex colour
// and the total light intensity at the vertex
vec4 lightedFragColor = Colour0 * (ambientLightIntensity + diffuseLightIntensity + specularLightIntensity);
FragColor = lightedFragColor;
}
Vertex Shader
#version 330
layout (location = 0) in vec3 Position;
layout (location = 1) in vec3 Normal;
layout (location = 2) in vec4 Colour;
out vec3 Pos0;
out vec4 Colour0;
out vec3 Normal0;
out vec4 CameraPos0;
uniform mat4 gModelToWorldTransform;
uniform mat4 gWorldToViewTransform;
uniform mat4 gProjectionTransform;
void main()
{
vec4 vertexPositionInModelSpace = vec4(Position, 1);
vec4 vertexInWorldSpace = gModelToWorldTransform * vertexPositionInModelSpace;
vec4 vertexInViewSpace = gWorldToViewTransform * vertexInWorldSpace;
vec4 vertexInHomogeneousClipSpace = gProjectionTransform * vertexInViewSpace;
gl_Position = vertexInHomogeneousClipSpace;
vec3 normalInWorldSpace = (gModelToWorldTransform * vec4(Normal, 0.0)).xyz;
normalInWorldSpace = normalize(normalInWorldSpace);
Normal0 = normalInWorldSpace;
CameraPos0 = vertexInViewSpace;
Pos0 = vertexInWorldSpace.xyz;
Colour0 = Colour;
}

Answer 1

you need to clamp the dot result from the saturation calculus because on the back side the result is negative and the pow can return a positive number instead of clamping it to zero.
float specularFactor = pow(clamp(dot(R, V),0.0,1.0), 0.1f);
Edit:
Also the V should be a vector pointing to the camera position, not to the vertex position in world space:
vec3 V = normalize(CameraPos0 - Pos0);