In this video tutorial, we will explore the Light generator through a practical example.
Video Transcript
Hello everyone! In this video tutorial, we will explore the Light generator through a practical example.
I will assume that you are already familiar with topics such as Generators and map Baking, as I covered them in previous video tutorials.
The Light generator allows you to create a layer mask by simulating the projection of light rays from a point in the virtual world toward the objects present in the scene, much like a Sun placed in the virtual environment. Because of this, it can be used to generate directional masks, meaning masks that are white on surfaces directly facing the rays and gradually darker on surfaces that receive less direct exposure. However, do not be misled by the generator's name, "Light": these rays are used only to generate the layer mask and have no effect on the color of the objects or on the scene's lighting. These are completely different effects.
Let me immediately show you the basic appearance of a mask generated with Light through a practical example.
I have imported an object, a traditional Japanese lantern, and assigned it the "Concrete Plain Brushed" material.
I will now add the "Iceland Snow" material at the top of the material's Layers stack. The idea is to apply the snow material only to certain parts of the object, specifically those that would be most exposed to snowfall. At the moment, however, the new material completely covers the original one, so we need a mask.
I will therefore add a black layer mask to the "Snow" material, then right-click the mask and add a Light generator.
Something is wrong: the generated mask is completely white, and the new material covers the one underneath. At a glance, we can see that a couple of maps are missing in the generator's Properties panel, so I will click "Bake Mesh Maps" in "Texture Set Settings" and have Substance create at least the two maps we need, "World Space Normal" and "Position" in this case.
"World Space Normal" stores information about the orientation of the object's various faces within the virtual world, while "Position" stores information about their coordinates, particularly their height.
These two maps are used by the Light generator to determine how strongly the object's faces will be affected based on their orientation in the scene and their height. Regarding orientation, we can adjust the direction of Light's rays using "Horizontal Angle" and "Vertical Angle" in the generator's Properties panel. The coordinate information stored in the "Position" map is useful for modifying the "Light Attenuation" parameter, allowing us to reduce the influence on the lower portions of the geometry.
Even though the generator's effect on the mask, and therefore on the material application, is clearly visible in Material view mode in the 3D View, especially if you enable and disable the "Iceland Snow" material to compare the results, I recommend switching to "Mask" view mode after selecting the layer mask. In my opinion, this makes it much easier to understand where the Light generator's rays are striking and with what intensity as you modify the two angle parameters and the light attenuation factor.
Mask view mode also allows you to directly observe the effect of the "Highlight Glossiness" and "Highlight Level" parameters. These settings let you increase or decrease the intensity of the illumination and therefore the gray levels in the generated mask, which in turn result in stronger or weaker application of the associated material, even on faces that are not directly hit by the light rays.
The Light generator therefore has only a few parameters, but they provide a reasonable degree of flexibility in applying the effect. I encourage you to think of other possible use cases for this generator.
Unfortunately, it is not all good news: the Light generator does not take self-occlusion into account. As a result, we can see that the surfaces inside the lantern are also affected by its rays. This happens because Light is based on the orientation of the geometry's faces, and the faces inside the lantern are still oriented upward.
To manually exclude those faces, we can proceed in several ways. One approach, for example, is to place the snow material inside a group, initially assigning a white layer mask to the group, and then manually excluding the areas we do not want, using either a brush or a polygon selection tool. In my case, I will use "UV Chunk Fill", set to 0, so that the UV islands of the mask become black when I click on them.
As with any other generator, it is also possible to apply filters and additional effects to Light. For example, we can add a Blur filter to soften the mask edges and make the transition areas less sharp, if desired.
Well, that concludes this tutorial! As always, feel free to leave any questions, comments, or requests in the YouTube video comments section. See you next time!