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Figure 25-14: The same rendering with shadows.

Creating Scenes

Scenes help you manage lights and views. For example, you can create two scenes: the first with only a distant light to mimic the effect of exclusively natural light; and another with no distant light but with point lights and spotlights to create a nighttime effect. You can also change the view so that you can look at the objects from different vantage points.

To create a scene, choose Scenes from the Render toolbar to open the Scenes dialog box, shown in Figure 25-15.This dialog box lists your scenes and enables you to create,

modify, and delete scenes.

Figure 25-15: The Scenes dialog box.

To create a new scene, follow these steps:

1.Click New to open the New Scene dialog box, shown in Figure 25-16. The New Scene dialog box lists all of the saved views and all of the lights that you’ve created.

2.Type a name in the Scene Name text box, no more than eight characters long.

3.Choose a view. You can choose only one.

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Figure 25-16: The New Scene dialog box.

4.Choose the lights that you want. Press Ctrl to choose more than one light. Press Shift to choose a range of lights. You can also choose *ALL* to quickly choose all of the lights for the scene.

5.Click OK.

Your scene is now listed in the Scenes dialog box. Click OK again to return to your drawing. When you render the drawing, you can choose this scene from the Render dialog box.

STEPS: Creating a Scene

1.If you have ab25-02.dwg open, use this file. Otherwise, open it from your AutoCAD Bible folder or the Results folder on the CD-ROM.

2.Save the file as ab25-03.dwg in your AutoCAD Bible folder. If the Render toolbar is not open, right-click any toolbar and choose Render.

3.Choose Scenes from the Render toolbar. Click New in the Scenes dialog box to open the New Scene dialog box.

4.Type morning in the Scene Name text box.

5.Choose RENDER1 from the Views list.

6.Choose D1 and P1 from the Lights list, pressing the Ctrl key while you select the second light.

7.Click OK twice to return to the drawing.

8.Save the drawing. If you’re continuing on to the next exercise, keep it open.

Working with Materials

Working with materials involves two steps: adding them to the drawing and attaching them to objects. Designing appropriate materials is an important part of the rendering process and

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greatly affects the results. Materials interact with lights. For example, shiny materials reflect light differently than dull materials because shiny materials create highlights. The object’s color affects how light appears on it as well.

Adding materials

AutoCAD comes with a large selection of materials. You can modify these to create your own materials. To add materials to the drawing, choose Materials Library from the Render

toolbar to open the Materials Library dialog box, shown in Figure 25-17.

Working with lists of materials

Materials are saved in a file with the extension .mli (materials library). The default materials library is render.mli. The left side of the Materials Library dialog box represents materials in the current drawing. The right side of the dialog box represents the entire list of materials provided by AutoCAD.

In the Current Drawing section, you can:

Click Save As to save the list of materials in the current drawing in an MLI file.

Click Purge to delete all of the materials in the list from the drawing.

Figure 25-17: The Materials Library dialog box.

In the Current Library section, you can:

Click Save to save changes to the entire library list in the MLI file in the current folder.

Click Save As to save the entire current library list in a new MLI file in any location.

Click Open to open a different library list and use its materials.

Importing and previewing materials

You often work with existing materials, but you should preview them first to make sure that they meet your needs. To add existing materials to your drawing, follow these steps:

1.Choose a material from the Current Library list on the right side of the dialog box.

2.Click Import.

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3.Choose the material from the Current Drawing list.

4.From the Preview drop-down list, choose the preview type of either Cube or Sphere, based on whether the object for which you want to use the material is flat or curved.

5.Click Preview to see a sample of the material.

6.Repeat Steps 1 through 5 until you have all of the materials that you want.

7.Click OK.

You can choose a range of materials by holding down Shift and clicking the first and last materials in the range. You can choose any nonconsecutive materials by holding down Ctrl and clicking the materials that you want.

If you don’t like a material that you’ve imported, highlight it and click Delete. Use the Export option to save materials that you’ve created in the drawing to the materials library file. When you click OK to close the Materials Library dialog box, AutoCAD asks you if you want to save the changes that you’ve made to the materials library file. Saving the changes updates the file.

STEPS: Importing Materials

1.If you have ab25-03.dwg open from the previous exercise, use this file. Otherwise, open it from your AutoCAD Bible folder (if you did the exercise) or the Results folder of the CD-ROM.

2.Save the file as ab25-04.dwg in your AutoCAD Bible folder. If the Render toolbar is not open, right-click any toolbar and choose Render.

3.Choose Materials Library from the Render toolbar. Hold down Ctrl, and scroll as

necessary to choose Beige Plastic, Green Glass, Light Wood Tile, Pink Marble, Stitched Pattern, White Matte, Wood Med. Ash, Wood White Ash, and Yellow Plastic. Click Import.

4.From the left list, choose Pink Marble. Choose Cube from the Preview drop-down list and click Preview to see the result. Do the same with Stitched Pattern.

5.Preview Green Glass with the Sphere.

6.Click OK. Save your drawing. If you’re continuing to the next exercise, keep the drawing open.

Creating your own materials

After you import materials from the materials library, you can modify them to create your own materials. Choose Materials from the Render toolbar to open the Materials

dialog box, shown in Figure 25-18.

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Notice that you can click Materials Library in this dialog box to open the Materials Library dialog box. You can therefore use the Materials dialog box to manage the entire process of importing, creating, and attaching materials. You can preview imported materials in this dialog box as well.

Figure 25-18: The Materials dialog box.

When you create a new material, you have three choices:

You can modify an existing material.

You can duplicate an existing material and then make modifications to the copy, leaving the original material intact.

You can start from scratch and create an entirely new material.

The dialog box that AutoCAD opens when you choose one of the preceding options depends on what you choose from the drop-down list below the New button. You have four choices: standard, marble, granite, and wood.

Standard creates a standard material.

Marble creates a material that mimics marble. In this dialog box, you specify turbulence and sharpness of the veins as well as the scale of the veins to the entire marble object.

Granite creates a material that mimics granite. In this dialog box, you can specify up to four colors and their sharpness (distinctness) as well as the scale of the texture relative to the entire granite object.

Wood creates a material that mimics wood. In this dialog box, you specify the light/dark ratio of the grain, the ring density and width, and the scale of the rings relative to the entire wood object.

When you choose a method of creating a new material, whether by modifying, duplicating, or creating from scratch, AutoCAD opens the dialog box appropriate to the material that you’ve chosen. Figure 25-19 shows the New Standard Material dialog box.

Unless you’re modifying an existing material, you first give the material a name in the Material Name text box.

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Figure 25-19: The New Standard Material dialog box.

You use this dialog box by choosing the attributes listed on the left side, one by one, and then specifying the values for each attribute from the choices on the right.

Color/Pattern

The color is the basic color of the object. The reflection of light off the object (called diffuse reflection) is determined by this color. You set the color in the Color section of the dialog box, using one of four methods:

Choose By ACI (AutoCAD Color Index). This option enables you to set the color to the color of the object in the drawing. You must uncheck this option to choose one of the three other methods.

Choose RGB from the Color System drop-down list to specify the color using the red- green-blue system. These are the three primary light colors. For each color, you can type in a value from 0 to 1 or use the slider bars. When all three are set to 1, you get white light.

Choose HLS from the Color System drop-down list to specify the color using the hue, lightness, and saturation system. Hue is the color; lightness, or brightness, is the amount of white that the color contains; saturation is the amount of black that the color contains.

Click the color swatch to open the Windows Color dialog box, which allows you to specify a color using either the RGB or the HLS system.

In addition to setting the color, you set the value. The value affects the surface finish and interacts with the reflection value. For example, AutoCAD recommends using a color value of 0.7 and a reflection value of 0.3 for a dull finish, and reversing these values for a shiny finish. You can type a value or use the slider bar. If you choose a bitmap (raster) file, the color becomes a pattern. See the “Mapping” sidebar for more information.

Ambient

The ambient color and value affect the color reflected by ambient light. Remember that you set the amount of ambient light when you created lights. You can click the Lock check box in the Color section of the dialog box to lock the ambient and reflection colors to the main color. (You cannot use Lock if you checked By ACI as the color.)

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Reflection

The reflection setting affects highlights created by light that shines on the object. To create a shiny object, you can use a reflection value of 0.7 with a color value of 0.3. Shiny objects often create a white highlight; for this effect, set the color to white by setting red, green, and blue to 1. You can also choose a bitmap file to create a reflection map. See the “Mapping” sidebar for more information.

Roughness

Roughness has no color setting; you only set a value. A rough surface produces smaller highlights; use a lower value to create smaller highlights. If you chose a zero value for reflection, the roughness setting is not used.

Mapping

AutoCAD lets you project a 2D image onto the surface of a 3D object. This is called mapping. You must use the Photo Real or Photo Raytrace rendering types to render with mappings. The 2D images are bitmap (raster) files that can be in several file formats, such as TGA, BMP, TIF, and JPEG. AutoCAD provides a large number of TGA files. To locate them, choose Tools Options and click the Files tab. Double-click Texture Maps Search Path. You can actually place up to four bitmaps onto an object. When you create a material, you can add bitmaps to the Color/Pattern, Reflection, Transparency, and Bump Map characteristics of a material.

Four kinds of maps correspond to the four characteristics:

Texture maps place a pattern of colors onto the object. When you include a bitmap in the Color/Pattern definition, you turn a plain color into a pattern.

Reflection maps place a scene on the surface of a reflective object, in the same way that you can see yourself reflected in a pool of water. Add a bitmap to the Reflection definition.

Opacity maps mimic areas of opacity and transparency. Add a bitmap to the Transparency definition.

Bump maps create the effect of varying heights. Choose Bump Maps and choose a bitmap file.

AutoCAD comes with a number of materials that include maps. In the Materials Library dialog box, some good examples include the Bumpywhite stone and Checker textures. As their names make clear, the first material is a bump map and the second a texture map. Import and preview them to see how they look. Using these materials saves you the task of specifying a bitmap file.

Bitmap Blend determines how much the bitmap is used. The values range from 0 (zero) to 1. For example, a 1.0 value for a bump map gives you the full value of the bumps. A lower value creates lower bumps.

Choose Adjust Bitmap to open the Adjust Material Bitmap Placement dialog box. Here you set the offset of the origin of the bitmap and the scale. The scale is the number of times the bitmap fits onto the object. If you’re unfamiliar with the bitmap, you’ll need to experiment. You can try various options and click Preview to see the results. Bitmapping uses U and V axes, which are like X and Y axes but can have any direction and origin. Click Maintain Aspect Ratio to keep the U and V scales equal.

By default, bitmaps are tiled, which means that if the scale is less than 1, AutoCAD repeats the pattern to cover the entire object. You can also crop, which creates a decal effect; the pattern is placed just once on the object.

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Transparency

The transparency setting enables you to create transparent or translucent materials. You set the value from 0 to 1. Higher values mean greater transparency. Keep in mind that using transparency increases rendering time. You can choose a bitmap to create an opacity map. See the “Mapping” sidebar for more information.

Refraction

Refraction applies only to Photo Raytrace rendering when you have a transparent (or translucent) material. Refraction is the bending of a light wave when it passes through an object to an object of another density. A higher value increases the refraction.

Bump map

Bump maps create the effect of varying heights on the surface of the object — in other words, bumps. You use the bottom part of the dialog box to choose the bump map and for bump-map settings. See the “Mapping” sidebar for more information about bump maps.

As you complete the dialog box, you can click Preview and see the result as a sphere or cube at any time. When you like the results that you see with Preview, click OK.

STEPS: Creating Materials

1.If you have ab25-04.dwg open from the previous exercise, use this file. Otherwise, open it from your AutoCAD Bible folder (if you did the exercise) or the Results folder of the CD-ROM.

2.Save the file as ab25-05.dwg in your AutoCAD Bible folder. If the Render toolbar is not open, right-click any toolbar and choose Render.

3.Choose Materials from the Render toolbar. The materials that were imported in the previous exercise are listed on the left. Choose Yellow Plastic and click Duplicate.

4.In the Material Name text box of the New Standard Material dialog box, type Yellow

Cheese.

5.With Color/Pattern selected from the Attributes section of the dialog box, click the color swatch to the right of the Color System drop-down list. In the Color dialog box, click the Index Color tab and pick the yellow box. Click OK.

6.Choose Ambient from the Attributes section. Click Lock in the Color section. The color changes to the same yellow as the Color/Pattern swatch.

7.Choose Reflection. Change the value to 0.10 because cheese isn’t very shiny. Click Lock here as well.

8.Choose Roughness. Change the value to 0.75.

You can omit transparency because its default value is 0 (zero). Refraction is irrelevant without a transparency setting.

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9.Preview the yellow cheese on a cube. Choose Bump Map from the Attributes section. Choose Find File at the bottom right of the dialog box. In the Bitmap File dialog box, the Textures folder should be current. (If not, find the Textures folder inside the main AutoCAD folder and double-click.) Change the Files of Type drop-down list to *.tga. Choose bmps.tga and click Open. Change the Bitmap Blend to .30. Click Preview again to see the difference. Note that the bumps are too big.

10.Click Adjust Bitmap. In the Adjust Bitmap Material Placement dialog box, and check Maintain Aspect Ratio. Change the scale to 2 and click Preview using the cube. The bumps are smaller now. Click OK three times to return to your drawing.

11.Save your drawing.

Attaching materials

After you import, create, and modify the materials that you need, you can attach them to objects. AutoCAD lets you attach materials by object, layer, or color. To attach any material, follow these steps:

1.Choose Materials from the Render toolbar.

2.Choose the material from the list of materials.

3.Use one of these methods to attach the material:

•Click Attach to attach a material by selecting the object or objects. AutoCAD temporarily returns you to your drawing and prompts you to select objects.

•Click By ACI (AutoCAD Color Index) to attach a material by its color in the drawing. AutoCAD opens the Attach by AutoCAD Color Index dialog box, which lets you choose a color, or colors, by their numbers.

•Click By Layer to attach a material by layer. AutoCAD opens the Attach by Layer dialog box, which lets you choose a layer or layers.

You can assign a material to an object, to its layer, and to its color, which would mean that the object has three materials. AutoCAD gives priority to direct attachments by object, then to attachments by color, and finally to attachments by layer.

STEPS: Attaching Materials

1.Open ab25-b.dwg from the CD-ROM.

2.Save the file as ab25-06.dwg in your AutoCAD Bible folder. If the Render toolbar is not open, right-click any toolbar and choose Render. This is the same drawing used earlier in the chapter, but all of the materials have been imported and modified, and some materials have been attached to objects. Also, the table and chairs have been separated into appropriate layers.