fixed background bug,

support directional light,
zoom speed can be adjust via +/-

QtMeshViewer/Resources/about.txt

@@ -8,6 +8,7 @@ left mouse - rotate
 right mouse - move
 scroll - zoom
 space - reset view
++/- - adjust zoom speed
 L - set light to current position
 esc - close
 

QtMeshViewer/Resources/fshader.glsl

@@ -15,7 +15,7 @@ uniform bool b_transparent;
 uniform bool b_light;
 
 uniform struct Light {
-	vec3 position;
+	vec4 position;
 	vec3 intensities;
 	float attenuationFactor;
 	float ambientCoefficient;
@@ -31,11 +31,29 @@ void main()
 	{
 		// some values
 		vec3 normalWorld = normalize(n_matrix * v_surfaceNormal);
+
 		vec4 surfaceColor = vec4(texture2D(texture, v_surfaceUV));
 		surfaceColor.rgb = pow(surfaceColor.rgb, vec3(2.2));
 		if(!b_transparent)
 			surfaceColor.a = 1.0f;
-		vec3 surfaceToLight = normalize(light.position - v_surfacePosition);
+		
+		vec3 surfaceToLight;
+		float attenuation;
+		// directional light
+		if(light.position.w == 0)
+		{
+			surfaceToLight = normalize(light.position.xyz);
+			attenuation = 1;
+		}
+		// point light
+		else
+		{
+			surfaceToLight = normalize(light.position.xyz - v_surfacePosition);
+
+			float distanceToLight = length(light.position.xyz - v_surfacePosition);
+			attenuation = 1.0 / (1.0 + light.attenuationFactor * pow(distanceToLight, 2));
+		}
+
 		vec3 surfaceToCamera = normalize(cameraPosition - v_surfacePosition);
 
 		// ambient
@@ -51,10 +69,6 @@ void main()
 			specularCoefficient = pow(max(0.0, dot(surfaceToCamera, reflect(-surfaceToLight, normalWorld))), materialShininess);
 		vec3 specular = specularCoefficient * materialSpecularColor * light.intensities;
 
-		// attenuation
-		float distanceToLight = length(light.position - v_surfacePosition);
-		float attenuation = 1.0 / (1.0 + light.attenuationFactor * pow(distanceToLight, 2));
-
 		// linear color before gamma correction)
 		vec3 linearColor = ambient + attenuation * (diffuse + specular);