Our next topic is Glow. Certain very shiny object for example the surface of the chandelier should produce some kind of glow or lens flare effect.
The first important thing is that our Camera here in the Render compound works in HDR mode: the HDR Out switch of the Camera is turned on. That means that the rendered output preserves the information regarding the high intensity surfaces.
Secondly, there is a Tone Mapper module inserted here in the processing chain. It maps the HDR images into the normal dynamic range and at the same time indicates the high intensity areas with various light effects. It has a property named “Bright Threshold”. It specifies the brightness value anything above this value causes the module to start to add the light effects.
If we take a closer look at the chandelier’s shader, we can see that it has a Luminosity value of 1.6. So it doesn’t yet cross the specified Brightness Threshold. One possibility is that we increase this Luminosity. Over the value 5 we can see the effects appearing. But it might be more practical to leave the luminosities specified in the model alone, and adjust the Tone Mapper’s properties instead. Let’s change the Brightness Threshold to 1.3 and the effects appear again.
We can choose which kind of effect are rendered. For e.g. now we turn off these blue anamorphic streaks and use plain glow instead. Glow is called “Bloom” in this context. Let’s adjust its intensity and its extent with the different properties until the effect meets our taste.
There is another path of creating glow effect. We mainly use it with colorful shiny surfaces like these neon figures here. As we can see there’s another Tone Mapper here which is connected to the misterious “Highlight Map” output of the Camera. What is this Highlight Map then? Let’s select the shader of the neon figure. Every shader has a “Highlight Color” property. If we push up its intensity, the object will appear on the Highligh Map output of the Camera and therefore goes through the second Tone Mapper. As you can see a glow immediately appears around the neon lady.
To be precise, using Highlight Map is a way to separate certain objects from the rest of the rendered image, and then to do whatever we want to do with them. In this case we apply a separate Tone Mapper to them thus making them glowing. If we take a closer look, the second Tone Mapper’s Brightness Threshold is set to zero. It means that anything coming out from the Highlight Map output gets a glow around it.
In other words, if we want a glow on any object, we simply push up its Highlight Color. Of course the properties of the glow effect itself are determined by the second Tone Mapper which can be parameterized completely independently from our main Tone Mapper used for HDR.
Let’s set the Highlight for all the necessary objects. For e.g. for the underwear of the lady here, and for the red sign. We can spot that the material of the sign is the same as the one used on the red reflective surfaces we dealt that before. So we have to be careful with the glow. I rather continue to adjust the glow viewing these objects. Let’s make it a very subtle glow. Of course we could clone the shader for the sign and set a separate Highlight on it. But now the same Highlight will do just fine for the sign, so leave it.
In the case we are unsatisfied with the general look of the scene, we can, for example, add an Adjuster module to the processing chain, preferably before the Tone Mapper. After that we can adjust Gamma, Brightness, Contrast, and the color and balance, so on. Now I don’t want to apply any of these so I turning off the module.