The 7th Basic Knowledge of Digital Man C4D: Natural Light

During the Spring Festival, under the bright sunshine, I reread the book Light for Visual Artists, which was featured by Richard Joo of England, and I was deeply touched. The author's research on the angle of light art is very thorough. It can be seen that the author loves nature, loves life, observes life and feels life. After reading it, I feel that this knowledge is very helpful for learning how to make indoor and outdoor renderings. Through retrospective study, I recorded some key points and restored them in the scene with three-dimensional software to share with my favorite friends.

theory

Part I: Basic part

The picture above is an environmental simulation of a sunny afternoon.

1, the main light source is the sun (the sun is a little yellow in the afternoon and warm and white at noon), which is the brightest and casts a clear shadow. The shape and color of the highlight are determined by it. The smaller the light source, the clearer the shadow.

2. The secondary light source is skylight. This is a huge light source. Blue light in sunlight is scattered by dust in the atmosphere, and huge blue ambient light is formed in the sky. The shadow it produces is very soft, but it is invisible in direct sunlight. Affected by it, places that are not exposed to sunlight will show blue tones, such as shadow parts and so on.

There is a third light source between the white background and the sphere, which is reflected light. Because the skylight is reflected between the bottom plate and the sphere, the shadow will not be very dark. Although the ground and the sphere are white, the sky environment can be illuminated by light, so it looks blue.

Highlights, shadows, and boundaries between light and shade: the brightest place is highlights, and its shape is basically determined by the shape and color of the sun (and of course the reflective properties of the surface, such as anisotropy). The darkest place is under the sphere, and neither sunlight nor skylight can illuminate it; The second is the dividing line between light and shade, which is the dividing line between the direct sunlight area (solar energy) and the backlight surface (sky ambient light and reflected energy).

The picture below shows a building with backlight. The backlit glass wall reflects the sky ambient light, and the marble wall below is also blue.

Shadows are illuminated by ambient light in the sky, showing a blue hue.

Simulation in 3D software

1, build a ground and give it a white material; Establish the sky (in C4D, the sky is a huge closed sphere), and give the luminous channel blue and darker brightness values; Create a high beam, set it to white, adjust the angle, and simulate sunlight.

2. In the previous 3D rendering software, there was no global illumination rendering engine, and most of them were line scanning surface rendering. Therefore, to simulate this effect, we must use a lot of lights: copy a beam of point light sources (there was no area light source at that time) to simulate the blue ambient light in the sky; Simulate sunlight with parallel light; Put a point light source behind the sphere to simulate reflection and weaken the shadow effect; If the ground is other colors, such as red, then a red point light source with very low brightness should be used to illuminate the back of the sphere to simulate the influence of radiation on the sphere.

However, by using the global lighting engine and making simple settings, the above effects can be achieved.

3. Global lighting engine, using a large number of photons in a closed space to simulate the real light bounce between objects for calculation, and the rendering effect can basically meet our requirements. Rendering is as follows:

Part II: Natural light in different periods.

Natural light source refers to the sun, of course, but at different times and in different weather, the sun shows different characteristics, either hard or soft, or cold or warm.

1, atmospheric scattering and cloud shielding.

Scattering: The earth's atmosphere scatters short-wavelength light waves in all directions, while long-wavelength light waves can travel a long distance (the wavelengths of red, orange, yellow, green, indigo and purple are shortened in turn). When the sun is not above the horizon or sinks below it, the scattered light in the sky is the only light source.

The following two pictures are the sunset glow. The inclination of the sun increases, the color of the sun warms, and the sun has a golden color. As the light intensity decreases, the sky becomes dark blue. One hour before sunset is called "prime time". At this time, the sunshine saturation is very high, the main light is warm and the shadow is complementary and cool, which is very beautiful.

Shadow effect of clouds: clouds are translucent. Although sunlight can penetrate clouds, it must be diffused, and light will spread in all directions (such as parallel light passing through ground glass). Clouds turn the sun's small and hard light source into a soft and big light source.

The picture below is cloudy. The sun was hidden by thick clouds. The sky is a soft luminous body with soft shadows and high saturation.

The picture below shows the plants in the shadow, with no highlights, soft shadows and high saturation.

The picture below shows the plants under the clouds with highlights on them.

2. The midday sun. When the sun rises to the highest point, the light is white, the strongest and the smallest shadow. Strong light lightens the color of an object (low saturation). There is a strong contrast between light and shade, and there are few details in the shadows.

The color of the building is white, the shadows are deep and sharp, and the contrast is strong.

3. In the evening and before sunset. As the angle of the sun becomes larger, the color of the sun becomes warmer and warmer, and the sun is obviously golden yellow. As the light faded, the sky turned dark blue.

4. at sunset When the sun is about to set, it turns into a dark orange and reddish color, and the sky turns into a deeper and thicker blue, with a particularly long shadow and obvious texture. The sky is especially bright when there are clouds.

5, dusk. The main light source in the sky is skylight. Soft light, less shadows and low contrast.

6. Good night. Although there is no sunlight, some light comes from the weak scattering of the sun, the light of the moon, starlight and artificial light.

The light at night is diffuse light with soft tones. The sky is always brighter than the scenery on the ground.

7. Cloud gaps and light spots: In nature, light and shadow are often intertwined. Cloud gap: the light lacks the blue auxiliary light of the sky, but the sunlight cast from the cloud gap is very strong and spots appear on the ground.

realize

1.CG It is very important for people to love nature, observe life and understand optical principles. We use computers to simulate reality. In your mind, you need to know what the reality is like, and you can't give it to the computer completely, otherwise the picture you make will feel uncomfortable and unreal. A friend who makes renderings told me that some authors' renderings are pure fabrications. For example, in a very clean and decorated room, the sunlight from the window appears very obvious light (Tindal phenomenon), which the author thinks is beautiful. In fact, if this happens, it shows that there is a lot of floating ash in the indoor air, otherwise, it is impossible to produce such light in a clean space. And in order to show the indoor lighting, many people make renderings. When there is plenty of sunshine during the day, the indoor lights are fully turned on, but the rendered lighting effect is very obvious. Obviously, this is unreasonable. If you show the lighting effect, just take a night view. (In order to save costs, the author may also make day and night in a picture, hehe)

Studying here is only a little knowledge. You really need to read more books and study more, and then you can observe life and photos.

This book is highly recommended (not an advertisement, but a really good book).

3. Supplement: In C4D, "physical sky" can be used to simulate "nature", and professional software VUE can also be used to make environment. I'll write an introduction when I have the chance.

Disclaimer: The pictures in the above presentation are all from the Internet, and are for study and research only, and have no commercial use.