Color of light

White light is refracted into seven colors after passing through the prism, which is the visible part of the white light spectrum, namely red, orange, yellow, green, blue, indigo and purple, abbreviated as ROYGBIV. Among these colors, red, green and blue are primary colors, so the color model of light is RGB model.

The mechanism of computer screen color generation can also be considered as RGB model, and most drawing programs (including 3D Studio MAX) provide RGB color selection mode. The following figure shows the RGB color model. It should be noted that the color of light is additive while the color of pigment is subtractive. The so-called additivity means that the more colors are mixed, the lighter the color is, and the opposite is true for subtraction. People who have studied color painting should be very clear.

RGB color model. Interestingly, when the multiplication value of RGB color changes from 1 to-1, the color will become the original complementary color, that is, the CYM color on the right.

In the world of 3DSMAX, the scene you see depends on the way you light it, and the scene presented is completely determined by the color and position of the luminous object. In fact, it is rare to use only white light to create an atmosphere. Using artificial light with few color components will make the scene lifeless. Cinemas generally use a variety of combinations of pure red, pure green, pure blue, pure yellow, deep red and blue-green, which makes some areas and many light columns look colorful. Light with high saturation should be used with great care, because it often distorts the facts, for example, under the yellow light of kerosene lamps, it is impossible to distinguish khaki from lemon yellow.

3DSMAX's lamp

The lights in the program are all simulated real-world lighting modes, such as Target Spot is a flashlight or searchlight model, and Omni simulates candlelight or sunlight in space; Parallel light simulates direct parallel sunlight in nature. These lights can be turned on or off, changing their size, shape and position, changing colors, turning shadows on or off, setting the flexibility of shadow edges, setting which objects are illuminated by all light, and even using particularly dark light to "absorb" excess light in some areas.

Exlude function is the first feature of MAX lighting. It can set which objects in the scene are affected and which are not. In a complex scene, some people set dozens of lights for the effect, which will inevitably cause some objects to be overexposed or even lose their shadows. Excluding them from the influence of some lights can keep the original effect.

The multiplier is similar to the dimmer of a lamp. A value less than 1 will decrease the brightness of the light, while a value greater than 1 will increase the brightness of the light. When this value is negative, the light actually subtracts the brightness of the scene. "Negative light" is usually used to simulate the effect of local darkness, and it is usually only placed in the inner corner to darken it, thus producing an effect that ordinary light in the scene is difficult to obtain.

Multiplier can use similar colors to keep a series of lights in the scene (below). However, if the RGB value is increased or decreased accordingly, the color of the sample will be difficult to identify.

From left to right, R=255, G= 10, B= 10, and multiplier =1; Multiplier =5. Multiplier = 10. Multiplier =20. Multiplier =26.

Whether to use attenuation is one of the reasons for the success or failure of many scenarios. MAX's lights are not attenuated by default, which usually means that the scene will soon become too bright. Remember, in indoor lighting, attenuation should be used for all lights except the darkest auxiliary light. In real life, due to the loss of light energy in the process of transmission, light will weaken with distance. It should be pointed out that in nature, light decays according to the reciprocal of the square ratio of distance. For example, the brightness of light is x at 10m and X/4 at 20M. But in most computer programs (including 3DSMAX), the attenuation of light is linear, that is to say, the brightness of light just now was X/2 at 20m.

The Playing Style and Influence of Light

In 3DSMAX, the default lighting is two lights at -X, -Y, +Z and +X, +Y,-z.. Once you set the lights in the scene, these two lights will automatically turn off.

There are several types of lighting available to MAX in photography.

Triangle lighting is the most basic lighting method, which uses three kinds of light sources: the main light is the brightest, which is used to illuminate most scenes and often casts shadows; Backlight is used to separate the object from the background and show the depth of the scene. It is often located at the back and upper part of the object, and its intensity is equal to or less than the main light. The auxiliary light is usually located on the left side of the camera, which is used to illuminate the black areas that are not illuminated by the main light and control the contrast between the brightest and darkest areas in the scene. Bright auxiliary light produces an average lighting effect, while dark auxiliary light increases contrast.

When the large scene cannot be illuminated by triangle, the section illumination method can be used to illuminate each small section, and the basic triangle illumination method can be used after the section is selected.

For highly reflective metal materials, it is sometimes necessary to surround light to express its texture, which is a relatively rare method.

The nature of light has a great influence on the scene. The harsh direct light comes from a point light source, which forms a strong contrast, and the texture and depth can be increased or decreased according to the direction of its irradiation. Soft light produces a dim light source, which helps to reduce contrast. The direction of light will also affect the composition of shapes in the scene. Soft light has no specific direction, and seems to come gently from all directions. There are three basic directions of harsh direct light: front light, side light and backlight.

Positive light energy produces a very striking effect, especially when it forms a strong contrast. However, this light will lose its shadow and make the scene lack perspective.

Side light can produce shadows across the picture, which is easy to show the texture of the object.

Backlight often produces a strong and obvious contrast, clearly showing the outline of the object.

Dark, cold and poorly lit places are suitable for sad, low or mysterious effects. Predict the unknown. Instead, it is high and low lighting, which can be used in bars and casinos, emphasizing the main object or role and obscuring others.

Bright, warm and clear shadows are suitable for exciting scenes, while changing to colder colors is a quiet atmosphere.

Lighting special effects

Although the lighting function of 3DSMAX is very powerful, some special effects, such as body lighting, neon effect and glare, need another program or plug-in.

Body light: Body light is a universal phenomenon in the world. Flashlight, searchlight and street lamp are all concrete examples of body light in foggy days at night. Body light is formed by light being scattered by dust particles in the air. In the computer three-dimensional world, there is only "vacuum" and no dust particles. You can create the effect of body lighting in the environment.

Luminous object effect

The luminous effect of neon lights or lasers cannot be created by light. Although it can be replaced by self-luminous materials in some cases, it is not strictly true. You need to add a glow effect (video paste/glow) to the self-luminous material.

Glare is actually the light spot produced by the camera lens, which can increase the authenticity of the scene to a certain extent. It is not good to use glare backlight. LensFlare, RealLens and GensisVFX provide the creation and flexible control of real glare. (Lens Glare [with Max] and GensisVFX are used as post-video plug-ins, and RealLens appears as an auxiliary object).

Shape of light source: 3DSMAX does not support true linear light source, which means it is difficult to achieve fluorescent lighting. MAX lighting can simulate the lighting effect of fluorescent lamps, but the effect is not satisfactory. RealLens provides a LumaObject function. LumaObject uses self-luminous objects as light sources, which can control the attenuation of light, thus achieving the effect of light energy transfer to a certain extent. The above picture shows the effect of using fluorescent lamp as LumaObject illuminator. Note that only one LumaObject is used here, and the rendering speed is extremely fast. In fact, LumaObject can use any shape of geometry or particle system as the light source.

Sunshine Simulation: There is a sunshine simulator in MAX, which can specify specific longitude, latitude, time and season to create local sunshine conditions. It has special value for architectural design, urban planning and lighting analysis, and the parameters can be animated to simulate the daily lighting situation of sunrise and sunset.

Ray operation

The rendering of 3DSMAX is linear scanning rendering. When you set the lighting for the scene, you will find out how far it is from reality. In this rendering mode, the light will not be reflected or refracted by the object, so unlike in the real world, a lamp can usually illuminate a bedroom. Many people have to hit dozens of lights when making a scene, and the number of lights when making animation is even more frightening.

At the same time, Grouraud and Phong shading algorithms provided by MAX are also inaccurate. They estimate the light falling on the surface, but they are not accurately calculated. To be completely accurate, you need light and light.

Ray tracing rendering tracks the rays between surfaces, and the rays are constantly reflected by some object surfaces to other object surfaces until they disappear from the scene. Ray tracing tracks the ray vector from the observation point to each surface. If the reflecting surface is a mirror, the auxiliary light will be reflected to capture the visible part of the reflected light. If light meets another mirror, they will be reflected again until the light exits the scene or is absorbed by the non-mirror. This is a typical ray tracing reflection generation process, so although the rendered image may be beautiful, it is also ray tracing.

Reasons for slow rendering.

The radiosity rendering method is very effective, but it requires a lot of calculation, which is longer than ray tracing. Ray tracing reflection only takes one observation point, and the reflected light finally finds an end point, while the reflected energy in the radiation model keeps rebounding in the scene, and the energy gradually weakens. Put a red ball near the white wall under strong light, and red appears on the white wall. This is the radiation effect.

RadioRay is a renderer that combines ray tracing and radiation, and its real ray calculation can create professional lighting effects. It can be used in architectural design, lighting design, exhibition design and other fields.

Light Color: Select a light and modify its color in the Modify panel.