Fix light_control example and update tutorial (#2149)

Signed-off-by: Ian Chen <[email protected]>

examples/standalone/light_control/light_control.cc

@@ -53,6 +53,7 @@ void createLight()
 
   entityFactoryRequest.mutable_light()->set_name("point");
   entityFactoryRequest.mutable_light()->set_range(4);
+  entityFactoryRequest.mutable_light()->set_intensity(1);
   entityFactoryRequest.mutable_light()->set_attenuation_linear(0.5);
   entityFactoryRequest.mutable_light()->set_attenuation_constant(0.2);
   entityFactoryRequest.mutable_light()->set_attenuation_quadratic(0.01);
@@ -149,6 +150,7 @@ int main(int argc, char **argv)
 //! [modify light]
     lightRequest.set_name("point");
     lightRequest.set_range(4);
+    lightRequest.set_intensity(1);
     lightRequest.set_attenuation_linear(0.5);
     lightRequest.set_attenuation_constant(0.2);
     lightRequest.set_attenuation_quadratic(0.01);

tutorials/light_config.md

@@ -7,17 +7,20 @@ This service will allow to modify lights in the scene.
 
 To modify lights inside the scene we need to use the service `/world/<world name>/light_config` and
 fill the message [`gz::msgs::Light`](https://gazebosim.org/api/msgs/9/classgz_1_1msgs_1_1Light.html).
-In particular this example modifies the point light that we introduced with the function `createLight()`.
+
+This tutorial describes the code in the `examples/standalone/light_control` example.
+
+First we create a point light with the function `createLight()`:
 
 \snippet examples/standalone/light_control/light_control.cc create light
 
 **NOTE:**: You can check the [entity creation](entity_creation.html) tutorial to learn how to include models and lights in the scene.
 
-As you can see in the snippet we modify the specular and diffuse colors of the light in the scene.
+As you can see in the snippet below, we then modify the specular and diffuse colors of the point light in the scene.
 
 \snippet examples/standalone/light_control/light_control.cc modify light
 
-In this case we are creating random numbers to fill the diffuse and specular.
+The `r`, `g`, `b` components of the light diffuse and specular colors are randomly generated and constantly changing:
 
 \snippet examples/standalone/light_control/light_control.cc random numbers