< https://yingyueue.myblog.arts.ac.uk/2 0 2 2 /1 1 /0 9 /lighting/>?

By Yingyue Feng?：< https://yingyueue.myblog.arts.ac.uk/author/20028722/

9th November 2022 ：< https://yingyueue.myblog.arts.ac.uk/2022/11/09/lighting/>

For lighting, I use 1 white main light source plus 2 colored special effect lights. I once learned how to light photography, and in this case, with one key light and two effect lights, I could do what I wanted. But photographic lighting belongs to real physical lighting in the real world. In Maya software, the software is used to simulate light. There is a certain gap in this aspect, but it is also very valuable for reference. And if the lighting can be adjusted during the lighting process, try to adjust it at one time, because the coloring and changes in the later stage often cannot replace the effect of the original lighting, especially the special effect light I plan to use. It is almost impossible to adjust to such an effect in the later stage.

Because my cat is white as a whole, but only white color will make the whole animation look very monotonous, especially after I will add white clouds, so I have to find a way to make the overall color more diverse, Otherwise, the wife is monotonous. So I plan to challenge one of the difficult problems in the design world, the colorful white.

Contrary to the colours used in painting, white light is a collection of all colours of light and it is impossible to add other colours to white light. When painting, mixing all the different colours of paint together, black will appear. And the situation with light is the exact opposite of what happens when painting. He discussed prism dispersion in great detail in his book Opticks (1704). He shone a beam of white light into a triple prism, which resulted in the refraction of different colours of light. This means that the white light contains all the other colours of light. Conversely, by superimposing all the different colours of light together, white light is formed. That is why it is almost impossible to add colour by light on a white object. Because white light already contains all the colours, no matter how much more light of other colours is added the result is white. And in many games the overall lighting is very dark. Not only for the sake of creating a scary atmosphere, but also because darker scenes can reduce more detail. And often times to reduce memory, and to speed up the computer. So ways are found to make the whole thing darker so that lower resolution mapping can be used, rougher modelling and the player can’t notice the details of the scene. And because my work is very white and very bright, more care must be taken with the details, otherwise any flaws will be magnified.

So it’s very difficult. The cat I made has white fur, and the scene I want to add later, such as the white cloud, is also white. So if I don’t want to increase the color of the whole work, the whole work will be black and white, which is very boring. I hope my work can have more colors and be more beautiful. But if you want to reflect white, you must use white light for irradiation. If the white cat is illuminated with light of other colors, then the cat will become another color, but if you want to reflect the whiteness of the cat, you can only use white light for illumination, then this work has There will be very few colors, only black, white and gray. So it is very difficult to add color to make the white cat colorful without changing its own color. What’s more difficult is that what I want to do is that the video is dynamic, so I can’t make all the colors fixed by painting, it will look very fake. This is the reason why brilliant white has become one of the conundrums in the design world. And I wanted to challenge that by making a colorful white cat.

The solution I chose was to use special effects lights to do it all, which is an advanced trick with lighting. First use a white key light to render the whole cat white, and then use two other special effect lights of different colors to color the shadow part of the whole cat. Since there is no way to change the color of the key light, which is the natural color of the cat, the best case scenario is to color the shadows to make it more colorful. In this way, more colors can be added to the whole scene without changing its inherent color, which is white, and because it is a shadow part, it will not appear too overwhelming. Whether it is special effect light or hidden color, it is a very difficult advanced skill.

Although the overall theoretical requirements are very complicated, in fact, only three lights are needed to complete it. First, the main light of No. 1 plus the special effect lights of No. 2 and No. 3. The more light, the better. When adding a lot of light sources in a mess, it is often unclear what effect you want, or how to increase the light to achieve the effect you want. Therefore, adding lights indiscriminately has no benefit other than increasing rendering time.

The white of the key light is very easy to adjust the value, as long as it is bright enough to show the natural white color of the cat, but also has enough shadows that I can increase the color of the shadows with the effect of light. The difficulty lies in the two special effects lights. I need to use special effect light to make the whole scene add more color to the dark side of the cat, but the light cannot exceed the key light, and the light produced by it cannot change the inherent color of the cat’s white color, which is very difficult. And what kind of lighting can be used to add more colors to show better effects, which also requires constant testing and consideration.

The last two effects lights I settled on were red and blue. These two colors are complementary and will be very noticeable together, and will have a very nice purple transition where they meet, so that there are at least three different colors. And after I adjust the brightness, it will not seize the natural white color of the subject. I have used many different colors, among which the color of the yellow light is very inconspicuous and cannot show its color, and because it is dark sleep, the light effect appears more gray than yellow. And many relative colors, such as red and green together or in the middle transition will appear very gray, which is not good-looking at all. So after I tried many times I ended up using red and blue as complementary colors for the two effect lights.

Finally, I rendered the whole animation and found something very interesting when looking at the effect. After I put the picture into photoshop or After Effects, it turned out that the color rendered by the light on the cat was not obvious. The cat is almost all white. But after I put the rendered picture into Davinci, I found that the color is very bright, which is very interesting, but it also increases the difficulty for me and the subsequent Compositing. I need to add color to the cat and cloud in After Effects Then put it into Davinci for final Compositing and export. This also meant that I was going to use the compositing software After Effects for grading, and then use the grading software Davinci for compositing.

There are still some small problems in the final rendered video, because I refer to the real-world photography lighting, but my work is an animation, the cat in the video is moving, and because it is the light calculated by the software . So after the final rendering, there are still two small problems in details, but the impact is not big.

First of all, when the cat turned around in the middle, because the left side of my two special effect lights was red light, and the right side was blue light, so the cat was on the right side at that time, so there was too much blue light. For this problem, unless the light moves with the cat, or the blue part is slightly reduced in post-grading, it can have a very good effect.

And the second small problem is that after the cat finally sat down, the light spot in the right eye was too bright. And this problem, so can not be changed. Because the reflected light spots in the eyes are the reflected main light, if the size or intensity of the main light is changed, it will have an impact on the overall brightness. If it is a real world light, then the overall brightness can be lowered. Change the main light source to ambient soft light and then add special effect light. Because in real-world photography, the brightness is not fixed and the absolute requirement is the light ratio. For example, the light ratio between my main light and my two special effect lights is about 10:2~10:1. So as long as the light ratio is kept constant and the overall brightness is reduced, the same effect can be produced. But because it is in the software, the intensity cannot be reduced, and because it is the main light, if the main light is not enough, the whole will be very dark, and the special effect light will overwhelm the guest and change the overall color, which will be even worse. This is also the difference between software lighting and real lighting.

【【3D 動(dòng)畫(huà)】貓毛發(fā)渲染】 https://www.bilibili.com/video/BV1MD4y1e7zH/?share_source=copy_web&;vd_source=eff7084a2b28118f094e7ee400f37ea2

https://www.youtube.com/embed/dqXlXYvgbZ0?feature=oembed