Light Linking techniques                                               Tutorial By: Srijesh

                       Light linking technique is simple but very important technique in Maya. We all know that in real world environment any object that is directly or indirectly exposed to any of the light source like sunlight, bulbs, fire etc. must be illuminated by that light source either by direct light beam or by reflected light beams. But in Maya, things could be different. In Maya we can create any kind of light like parallel, ambient, point, spot, area and volume and decide whether that light should illuminate certain objects that we have created or imported, or not. That means we can customize the illumination environment in Maya view port. That’s why Maya environment i.e. view port is flexible in many senses than real world environment.
                                      For this tutorial I’ve modeled two very simple nurbs beer bottles. In one bottle I’ve assigned red blinn material and in another bottle blue blinn material. I’ve renamed blue blinn shaded bottle to BlueBottle and red blinn shaded bottle to RedBottle. Along with these two bottles I’ve created a polygon cube base with checkered blinn material assigned as shown in figure below.

Fig. 1

                   Now let’s create a point light (create>point light) and place it in such a way that it illuminate both bottle equally. Let’s also enable the light’s depth map shadow feature. Now if we render them the output will be as below.

Fig. 2

              We can see that the light is illuminating both bottles in equal basis, because the point light is linked with both bottles. Now if we want that light not to illuminate the blue bottle only is it possible? Yes it is. For this we have to do as below.
                Go to Window>Relationship Editors> Light Linking. There you will see two options, Light-Centric and Object-Centric. In light centric objects can be connected or disconnected to the certain light based on that light. Whereas based on that objects in object centric. Let’s open Light-Centric window. In that window is separated in two columns, Light Sources and Illuminated Objects. In Light Sources column there are two light sources, one is default light sources and another is the point light that we’ve created before. Where as in Illuminated Objects column there are three models along with their shading groups as below.

Fig. 3

              Now if we click on pointLight1 of Light Source the whole objects of Illuminated Objects will be highlighted in gray. That’s because the point light is connected to the all of the objects in the view port. Let’s click on BlueBottle. This will remove highlight from it and will be disconnected from the point light as figure below.

Fig. 4

Now if we render the scene the output will be as below.

Fig. 5

               Since the point light has disabled default light sources and the blue bottle has been disconnected from the only light source in the view port i.e. pointlight1 the blue bottle is completely dark. In the same we also can disconnected the red bottle with the point light. The output render will be as below.

Fig. 6

In the same way we can connect and disconnect any light sources with any objects or models in view port.