Standard Material
The Standard material type provides a fairly straightforward way to model surfaces. In the real world, the appearance of a surface depends on how it reflects light. In 3ds Max, a standard material simulates a surface's reflective properties. If you don't use maps, a standard material gives an object a single, uniform color.
Standard Color Components
A surface of a "single" color usually reflects many colors. Standard materials typically use a four-color model to simulate this. (This can vary, depending on which shader you use.) The four colors are known as the material’s color components.
- Ambient color appears where the surface is lit by ambient light alone, where the surface is in shadow.
- Diffuse color appears where light falls directly on the surface, where the surface is in “good” lighting.
This component is called "diffuse" because light striking it is reflected in various directions. Highlights, on the other hand, are reflections of light sources.
- Specular color appears in highlights. Shiny surfaces usually have specular highlights, where the viewing angle is equal to the angle of incidence.
A surface can also have glancing highlights, where the angle of incidence is high, relative to the observer or camera (that is, the light ray is nearly parallel to the surface). Glancing highlights are characteristic of metallic surfaces.
Some surfaces are completely reflective, or nearly so. These reflect their environment as well as the light sources that illuminate them. To model such surfaces, you need to assign a Reflection map or use ray tracing.
- Filter color is the color transmitted by light shining through the object.
Note: The Raytrace material uses a different, six-color model to simulate surfaces. Several components are similar to those in the Standard Material, but they behave differently in Raytrace.
The three color components blend at the edges of their regions. Between ambient and diffuse, the blending is calculated by the shader. Between diffuse and specular, you set the amount of blending by using the Standard material's highlight controls.
When we describe an object's color in conversation, usually we mean its diffuse color. The choice of an ambient color depends on the kind of lighting. For moderate indoor lighting, it can be a darker shade of the diffuse color, but for bright indoor lighting and for daylight, it should be the complement of the primary (key) light source. The specular color should be either the same color as the key light source, or a high-value, low-saturation version of the diffuse color.
Warning: When you change the shading type of a material, you lose the settings (including map assignments) for any parameters that the new shader does not support. If you want to experiment with different shaders for a material with the same general parameters, make a copy of the material before you change its shading type. That way, you can still use the original material if the new shader doesn't give you the effect you want.
Other Standard Material Components
A standard material's specular color appears in highlights. You can control the size and shape of the highlight. A polished surface has a small and strong highlight. A matte surface has a large, weak highlight, or no highlight at all.
Standard materials also have controls for making the object appear transparent, and for making it self-illuminating so that it appears to glow.
Along with the material's color components, components also refers to the parameters that control highlights, transparency, self-illumination, and so on.
Shader Basic Parameters Rollout
The Shader Basic Parameters rollout lets you choose the type of shader to use with a Standard material. Some additional controls affect how the material appears.
- On the Shader Basic Parameters rollout, open the shader drop-down list.
- Click the name of the shader type to use for the active material.
- On the Shader Basic Parameters rollout, turn on Wire.
The material is now shaded as a wireframe mesh. The wire portions of the geometry do not change; color components, shininess, and so on, remain the same.
For a wireframe material, turn on the 2-Sided option as well.You have two choices for how wireframe materials are rendered. The controls for tuning wireframe shading are on the Extended Parameters rollout.
If you choose Pixels, the thickness of the wires maintains the same apparent thickness regardless of the scale of the geometry or how near or far the object is positioned. In other words, pixel wires have a constant display size as if the wires were traced over an image.If you choose Units, the wires behave as if they were modeled in the geometry. They appear thinner at a distance and thicker at close range. Scaling a wireframe object does scale wire width.
Chooses a shader. The material's Basic Parameters rollout changes to show the controls for the shader you choose.
These are the basic material shaders:
· Blinn (The default): For rounder, softer highlights than Phong shading
· Metal: For metallic surfaces
· Multi-Layer: For surfaces with more complex highlights than Anisotropic
· Oren-Nayar-Blinn: For matte surfaces such as fabric or terra cotta
· Phong: For surfaces with strong, circular highlights
· Strauss: For metallic and nonmetallic surfaces
· Translucent: Lets you specify translucency, where light is scattered as it passes through the material
Wire
Renders the material in wireframe mode. You can set the size of the wire in Extended Parameters.
2-Sided
Makes the material 2-sided. Applies the material to both sides of selected faces.
Face Map
Applies the material to the faces of the geometry. If the material is a mapped material, it requires no mapping coordinates. The map is automatically applied to each facet of the object.
Choosing Colors for Realism
Indoor and Outdoor Lighting
Whether a scene is indoors or outdoors affects your choice of material colors, just as it affects the way you set up lights. Full sunlight is bright and unidirectional. Most indoor lighting is less intense and more even (that is, multidirectional) than daylight. However, some special indoor lighting (and nighttime outdoor lighting), as for the stage, also features intense, directional light.
Direct sunlight has a yellow tint. Materials for objects to appear in daylight should have a specular color of a pale, unsaturated yellow (for example, RGB values of 240, 240, 188). The ambient color should be the complement of the specular: a deep, dark purple with a hint of the diffuse color.
Materials for objects to appear under normal interior lighting should have a specular color that is close to white. (Our perception compensates for the yellow or green tint that is often present in artificial light.) The ambient color can often have the same hue as the diffuse color, but with a darker value.
Materials for objects to appear under spotlights should follow the general guidelines for daylight materials. The specular color should match the spotlight's color, and the ambient color should be a very dark value of the spotlight color's complementary hue, mixed with a bit of the material's diffuse color.
Representing Natural Materials
Outdoor scene with natural materials
Most natural materials have a matte surface with little or no specular color. For natural materials such as these, use the following guidelines:
- Ambient color: The ambient color depends on whether the scene is indoors or outdoors, as previously described.
- Diffuse color: Choose a color found in nature. It is best to use the observed color of the object itself, or a similar object.
- Specular color: Make the specular color the same hue as the diffuse, but with a higher value and a lower saturation.
- Glossiness: Set the Glossiness to a low value.
Some foliage, bird feathers, fish scales, and so on, are shiny. For materials such as these, set the Glossiness to higher values. You might also want to change the specular color so it's closer to the lighting color than the surface's diffuse color.
Water is reflective, and is best modeled by a color component in combination with a reflection map or a water map.While metal is a natural material, its special visual characteristics are most apparent when it has been polished.
Representing Manufactured Materials
Manufactured materials often have a synthetic color rather than an "earth tone." Also, many manufactured materials, such as plastics and porcelain glazes, are very shiny. For manufactured materials, use the following guidelines:
- Ambient color: The ambient color depends on whether the scene is indoors or outdoors, as previously described.
- Diffuse color: Although the diffuse color doesn't have to be an "earth tone," as with natural materials you should used the observed color of the object or a similar object.
- Specular color: Make the specular color close to white, or to the color of the light source. White is especially characteristic of plastic materials.
- Glossiness: Set the glossiness to a high value.
Representing Metallic Objects
Metallic cup and ice cream scoop
Polished metal has a characteristic "glancing" highlight that appears where the light is at a high angle of incidence. To generate this effect, Metal shading uses the Cook/Torrance illumination model.
For metallic materials, you can use the Metal shading type. This disables the specular color and highlight controls. The Metal shader calculates its own specular color, which can vary between the diffuse color and the color of the light.
In the diffuse region of a metal material, the ambient component is greater than it is for other kinds of materials.
The Anisotropic, Multi-Layer, and Strauss shaders give you further options for modeling polished metal.
If the metallic object is the focus of the scene, you can improve realism by using a Blend material to combine metallic shading with a reflection map.
Tip: When you preview metallic surfaces, it is useful to turn on a backlight. This displays the metal's glancing highlight. The Backlight button is to the right of the sample slots.
No comments:
Post a Comment