Types of Rendering Supported by AutoCAD

AutoCAD 2002 incorporates a full-featured rendering engine that is capable of producing rendering ranging from simple shaded models to full photo-realistic renderings. Generally, three types, or levels, of rendering are offered by the rendering facility inside AutoCAD 2002:

• Render

• Photo Real

• Photo Raytrace

These three different types of rendering produce increasingly more realistic outputs, of which Photo Raytrace is the most realistic. You pay a price for realism, however: Increased realism requires increased rendering times.

The line of demarcation between shading and rendering is somewhat arbitrary. The shading modes available with the SHADEMODE command (discussed in Chapter 27, “Introduction to 3D”) could be considered simple rendering because the surfaces of a model are depicted as they appear with a single light source. AutoCAD’s RENDER command, however, takes up where simple shading leaves off, providing the ability to apply materials to surfaces, to supply various types of lighting, and to cast realistic shadows. The three levels of rendering offered with the RENDER command are summarized here:

• Render. Basic Render is the next logical step beyond the Gouraud shading mode offered by the SHADEMODE and 3DORBIT commands. Render mode has the added advantage of allowing you to assign materials to surfaces. You can assign materials such as brick, chrome, and wood to objects in the model on a per-layer, per-color, or per-object basis. In addition, you can add any of three types of light sources to the scene. In the basic Render mode, however, light sources are not capable of casting shadows. Other enhancements, such as backgrounds and plants, are also supported. Figure 31.1 shows a typical rendering using the Render mode.

  Figure 31.1. Typical rendering using the Render mode of the RENDER command. Note the absence of shadows.

  

• Photo Real. The Photo Real mode shares all the features of Render mode, but adds the ability to cast shadows and to use bitmaps for materials (see Figure 31.2).

  Figure 31.2. Typical rendering using the Photo Real mode of the RENDER command. Shadows and materials are present.

  

• Photo Raytrace. Photo Raytrace provides the most realistic renderings. It adds the ability to generate reflections, refraction effects, and true detailed shadows. Figure 31.3 shows a rendering using the Photo Raytrace mode.

  Figure 31.3. Typical rendering using the Photo Raytrace mode of the RENDER command. Note the presence of shadows and reflections.