You can see “Max reflection” in export setting. Even though you set “On”, images are not changed well in many cases. There must be a lot of people who are thinking “I can not understand this function”.
（2020.03.12 P.S.）In new version 2020.1, the function name changed to “Refinement” and the effect also seems to be changed a little. This article was wrote using ver. 2019.
（2020.03.28 P.S.）I got “Refinement” effects not only to reflection but also SSGI. Please see an article below.
I made a scene with windows. For understanding easily, opacity of windows is set as 100%. (These are almost mirrors!)
Twinmotion and UE4 use SSR (Screen Space Reflection) algorithm for computational reduction. Simply say, windows reflect objects only which are in viewport, with blurred background.
Now let’s render with Max reflection On/Off.
Please attention to the reflection of the man. When off, only his upperbody was reflected, but when on, his below the knee was included. It means that extended range of viewport became to influence to the reflection as shown in below.
（Now I got what this icon means!）
Anyway, this reflection by SSR looks not so good with strange blur. If you want to get more beautiful window of mirror, you can use Reflection Probes. It is not so much accurate reflection because it also uses simplified algorithm, but it is useful for making good-looking glass with weak reflection. Please refer to the amazing tutorial movie by askNK.
So, after all, is Max reflection useless feature? Let’s see another example.
The appearance of the floor tiles with strong reflection was changed a lot. It is because wider range of the sky was influenced to the reflection by using Max reflection.
Max reflection is also useful in waterside scenes as below. When Off, water surface in the front looks dark, but when On, the color of the water surface looks more beautiful reflecting sky color.
- Max reflection is not so useful for window and mirror, but useful for gleaming floor and water.
- Max reflection influences all object with reflection value, so whole image becames a little bit bright. Also, shadow appearance changes for some reason. If you don’t want to change result image from viewport, you may turn off Max reflection.
That’s all, thank you．