Chapter 24 Working with Cameras 661

Setting Camera Parameters

When a camera is first created, you can modify the camera parameters directly in the Create panel as long as the new camera is selected. After the camera object has been deselected, you can make modifications in the Modify panel’s Parameters rollout for the camera, shown in Figure 24-5.

Figure 24-5: The Parameters rollout (shown in two parts) lets you specify Lens values

or choose from a selection of stock lenses.

Cross-	Multi-pass cameras can be set up to create Depth of Field and Motion Blur effects. These
Reference	effects are covered in Chapter 26, “Multi-Pass Camera Effects.”

Lens settings and field of view

The first parameter in the Parameters rollout sets the Lens value or more simply, the camera’s focal length in millimeters.

The second parameter, FOV (which stands for field of view), sets the width of the area that the camera displays. The value is specified in degrees and can be set to represent a Horizontal, Vertical, or Diagonal distance using the flyout button to its left, as shown in Table 24-2.

	Table 24-2: Field of View Buttons
Button	Description
	Horizontal distance
	Vertical distance
	Diagonal distance

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The Orthographic Projection option displays the camera view in a manner similar to any of the orthographic viewports such as Top, Left, or Front. This eliminates any perspective distortion of objects farther back in the scene and displays true dimensions for all edges in the scene.

Professional photographers and film crews use standard stock lenses in the course of their work. These lenses can be simulated in Max by clicking one of the Stock Lens buttons. Preset stock lenses include 15, 20, 24, 28, 35, 50, 85, 135, and 200mm lengths. The Lens and FOV fields are automatically updated on stock lens selection.

Tip	On cameras that use 35mm film, the typical default lens is 50mm.

Camera type and display options

The Type option enables you to change a Free camera to a Target camera and back at any time.

The Show Cone option enables you to display the camera’s cone, showing the boundaries of the camera view when the camera isn’t selected. (The camera cone is always visible when a camera is selected.) The Show Horizon option sets a horizon line within the camera view, which is a dark gray line where the horizon is located.

Environment ranges and clipping planes

You use the Near and Far Range values to specify the volume within which atmospheric effects like fog and volume lights are to be contained. The Show option causes these limits to be displayed as yellow rectangles within the camera’s cone.

You use clipping planes to designate the closest and farthest object that the camera can see. In Max, they are displayed as red rectangles with crossing diagonals in the camera cone. The Clip Manually option lets you specify the Near Clip Plane to be something less than three units. Figure 24-6 shows a camera with Clipping Planes specified. The front Clipping Plane intersects the car and chops off its front end. The far Clipping Plane intersects the middle of the car and clips the back-end of the car as well as the construction grid.

Tip	Clipping planes can be used to create a cutaway view of your model.

Camera Correction Modifier

To understand the Camera Correction modifier, you first need to understand what 2-point perspective is. Default cameras in Max use 3-point perspective, which causes all lines to converge to a vanishing point off in the distance, but 2-point perspective causes all vertical lines to remain vertical.

The visual effect of this modifier is that extra tall objects appear to bend toward the camera when corrected. For example, if you have a camera pointed at a skyscraper, then correcting the camera with the Camera Correction modifier makes the top of the building appear closer rather than having it recede away.

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Near clipping plane

Figure 24-6: A camera cone displaying Clipping Planes

The Camera Correction modifier has an Amount value that lets you specify how much correction to apply and a Direction value that orients the angle of vertical lines in the scene. There is also a Guess button, which automatically sets the correction values for you based on the Z axis vertical.

Note	The Camera Correction modifier doesn’t appear in the Modifier List in the Modifier Stack, but
	you can select it from the Modifiers menu.

Figure 24-7 shows a windmill object with a simple Box positioned behind it. In the left image, notice that the windmill recedes away from the camera, which is positioned at the base of the windmill, but the right image has been camera corrected.

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Figure 24-7: Applying the Camera Correction modifier reorients the camera perspective.

Summary

Cameras can offer a unique look at your scene. You can position and move them anywhere. In this chapter, you discovered how cameras work and how to control and aim them at objects.

The Camera Match and Camera Tracker utilities enable you to match your scene’s position and motion to a background image or animation. These features can be very helpful in creating realistic images and animations.

In this chapter, you’ve

Learned the basics of cameras

Created a camera object and view

Discovered how to control a camera

Aimed a camera at objects

Changed camera parameters

Learned to correct camera perspective with the Camera Correction modifier

The next chapter deals with matching a camera to the perspective of a background image and tracking a camera’s movement for a background animation.

Matching and

Tracking Cameras

At times you’ll want to integrate your rendered images with an existing background image or a background animation

sequence. To do this, Max includes two unique utilities — Camera Match and Camera Tracker. The Camera Match utility can fit rendered scenes into an existing background image by matching the camera’s position to the perspective of the image. The Camera Tracker utility can reproduce a camera’s motion using an animated background.

Matching a Camera to a

Background Image

You use the Camera Match tool to align a camera’s position to the background image. After you align the camera to the position that was used to take the image, you can place 3D objects within your scene and be assured that they will line up correctly with the objects within the image. For example, if you take a picture of a street scene and align the camera with the background image, then any cars or buildings that you digitally add to the scene are correctly aligned.

You can find the Camera Match tool in the Utilities panel. Before you can use this tool, you need to load a bitmap image as a background. To do so, open the Environment dialog box by choosing Rendering Environment (or by pressing the 8 key).

Cross-	Chapter 41, “Rendering Basics,” provides more details on loading
Reference	and working with environment maps.

After a bitmap image loads as an environment map, make the background visible in the viewport by choosing Views Viewport Background (Alt+B) to open the Viewport Background dialog box. Here, you can specify a background source image or use the environment map you just loaded.

Setting Camera Match points

25C H A P T E R

In This Chapter

Using the Camera Match utility to match a camera to the background image

Tracking animation points with the Camera Tracker utility

After a background image loads and is visible in the viewport, you need to create Camera Points in the scene. These Camera Points

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identify specific locations within the bitmap and help match them to scene dimensions. To create the Camera Points, select Create Helpers Camera Point.

The Camera Match utility needs to have at least five Camera Points defined before it can create a camera. You should position these Camera Points in the scene at precise coordinates that match the background image. For example, if the distance between two points is four feet, then create the Camera Points such that they are four units from each other. In the Keyboard Entry rollout, you can create new Camera Points by entering exact XYZ values.

Note	To help keep the Camera Points straight, you can name each Camera Point by typing a name
	in the Name field. This helps when you try to identify each point in the Camera Match utility.

After positioning the Camera Points, open the Utilities panel and click the Camera Match button in the Utilities rollout. The Camera Point Info rollout, shown in Figure 25-1, includes a list of Camera Points. Each Camera Point needs to be assigned an XY position that matches its 3D location to a 2D position on the background bitmap. To assign these positions, click the Assign Position button, select a Camera Point from the list, and click the location in the viewport where this point should be positioned. You can also enter the X and Y coordinate values for the selected position in the X and Y fields in the Camera Point Info rollout.

Figure 25-1: After the position of each Camera Point is identified, you can create a camera.

As you line up the Camera Point positions, the bottom of the Camera Match rollout shows the current camera error. If the error value is greater than 5, the camera can’t be created. The Use This Point option can disable a Camera Point without deleting it, which can help you pinpoint the Camera Point that is misaligned.

The Create Camera button creates a camera after all the Camera Points have been correctly positioned. The Modify Camera button lets you realign Camera Points and change the current camera position. The Iterations value determines the number of calculations required to position the camera; if your error values are too high, try reducing this number and creating the camera again. The Freeze FOV (field of view) option prevents the FOV from changing as a camera is created.

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Tutorial: Driving in Rome

The streets of Rome are narrow and intricate — maybe because they need to wind around all the ancient structures. In this tutorial, those streets provide a perfect opportunity to practice using the Camera Match utility.

To match a camera view to a background image, follow these steps:

1.Open the Rome – matched camera.max file from the Chap 25 directory on the CD-ROM.

This file has the background image already loaded and visible in the viewport. This file also has the Porsche model created by Viewpoint Datalabs imported.

2.Now assign Camera Points throughout the scene. Select Create Helpers Camera Points and click in the Perspective view six times to create six Camera Points. Then select the first Camera Point, and click the Select and Move button (W). Then open the Move Transform Type-In dialog box by choosing Tools Transform Type-In (or by pressing the F12 key). Give the Camera Points the names and dimensions in the following list. Enter the dimensions in the Absolute column on the left.

•Left base of pillar: X = 0, Y = 0, Z = 0

•Right base of pillar: X = 10, Y = 0, Z = 0

•Left edge of wall: X = –10, Y = 0, Z = 0

•Right edge of wall: X = 20, Y = 0, Z = 0

•Right end of structure: X = 0, Y = 20, Z = 0

•Top of pillar: X = 0, Y = 0, Z = 30

Note Although accurate measurements are better, these dimensions are relative approximations (because I didn’t have time to fly to Rome with a tape measure).

3.After you position the six Camera Points, click the Camera Match button in the Utilities panel. In the Camera Point rollout is a list of the Camera Points that you’ve created. For each Camera Point in the list, click the Assign Position button, select the point, and click the background image where it is located. The following list has the exact dimensions that you can use to check your placement. When you’re finished, click the Assign Position button again to exit position selection mode.

•Left base of pillar: X = 279, Y = 324

•Right base of pillar: X = 322, Y = 346

•Left edge of wall: X = 236, Y = 306

•Right edge of wall: X = 372, Y = 370

•Right end of structure: X = 358, Y = 305

•Top of pillar: X = 278, Y = 144

4.After you’ve positioned all Camera Points, click the Create Camera button. If the current camera error value is less than 5, a camera appears in the scene. You can update the Camera Point positions by clicking the Assign Position button, selecting a Camera