INSIDE 3DS MAX® 7 [Electronic resources] نسخه متنی

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INSIDE 3DS MAX® 7 [Electronic resources] - نسخه متنی

Adobe Creative Team

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  • Rendering to a Background


    Frequently renderings are required to be composited into a scene that sits on top of a background plate. Most likely a rendering will be composited into the scene later, but the lighting and camera angle must match an existing shot. The lights are fairly straightforward, but getting the camera angle perfect can be a real pain. Fortunately, we can rely on the Camera Match utility to assist us.

    This utility enables CameraPoint helpers on the scene to be married to their counterparts in the background plate. The basic rules are that you need at least six points of reference, and they cannot be all coplanar. This requires careful measurement of the physical space. Exact-scale models are built in 3ds max, and the matching process can be completed. Figure 19.24 is an example of 3D geometry rendered over an existing background.

    Figure 19.24. The crypt background plate with a door rendered over it.

    To shed some light on the process, let's examine the preparations that the author undertook. First came the concept of the setting: a full moon in a cemetery, as a crypt door swings open. There happened to be a suitable cemetery nearby, so the author armed himself with tape measure, notepad, and digital camera. Shots were taken of the crypt and a pair of doors, and measurements were jotted down along with a rough sketch. After an uncomfortable interrogation by the cemetery's creepy sexton, the author adjourned to his studio to prepare the files.

    The original scene (Figure 19.25) was darkened by using Levels Adjustment in Photoshop and given a bluish tone with Hue/Saturation Adjustment. Additional darkening was spotted in with the Burn tool. Finally, the shot was cropped to 720 by 480 pixels, digital video size. The door shot (Figure 19.26) was dismantled and the pieces reassembled to make a single opaque door (Figure 19.27). A bump map was hand-built to give the door added dimension (Figure 19.28).

    Figure 19.25. The original shot of the crypt.

    Figure 19.26. The original shot of the doors to be modified.

    Figure 19.27. The final texture map of the now single door.

    Figure 19.28. The bump map of the door.

    From the field dimensions, a box was built in 3ds max to match the door opening of the crypt. The texture was applied, and the door lit and animated. We are now ready to add the camera and get a match with the background plate.

    The Door to the Crypt


    Let's follow the steps needed to modify the door of the crypt.


    1.

    Open the file called cryptStart.max from the DVD. From the File menu, choose Save As, point to an appropriate subdirectory on your hard drive, and click the plus-sign button to save a new file with the name incremented to cryptStart01.max.

    2.

    Go to Rendering > Environment, click the Environment Map button, select Bitmap, and choose cryptBack.tga from the list. Close the window when you have completed the selection.

    3.

    Click anywhere in the Perspective viewport to select it. Press the hot key G to remove the grid. Choose Views > Viewport Background, then click the Background Source Files button. Select the cryptBackTemp.jpg file. In the Aspect Ratio section, click the Match Rendering Output button, and make sure that Display Background is active. Click OK to close the window.

    Note

    You could use the Use Environment Background check box to place your template, but as the picture is dark, a special version with notes has been prepared to make the alignment job easier.

    4.

    Back in the Perspective viewport, right-click the window's title and change the view to Wireframe.

    As you can see in Figure 19.29, the door isn't anywhere near the right place in the scene. We need to mock up the main walls of the crypt to aid placement. Our field notes tell us that the main walls of the building are 9'11" wide, 6'10" tall, and 12' deep. We'll next build a box to those dimensions.

    Figure 19.29. The door resting against the background.

    5.

    Choose Customize > Units Setup > US Standard, Feet w/Fractional Inches. Click OK to close the dialog.

    6.

    Draw a box whose dimensions are 12' in length, 9'11" in width, and 6'10" in height. Visually align it so that it is flush with the bottom and sides of the door. See Figure 19.30 for reference.

    Figure 19.30. The mock-up box is aligned to the existing door.

    [View full size image]

    7.

    In the Front viewport, draw another box that is 3'7" in width, and whatever in the other dimensions. Still in the Front viewport, drag-clone a copy in the X axis. Move these boxes into place to align the door right in the middle of the wall (Figure 19.31). Once the boxes are located, a good approximation of the center of the wall can be made. Delete the boxes when you have the door placed in between them.

    Figure 19.31. Two temporary boxes aid in door placement.

    [View full size image]

    8.

    In the Perspective viewport, use the Arc Rotate and Zoom controls to put all of the front corners and the two back ones into view (Figure 19.32). Maximize the viewport for a better view.

    Figure 19.32. Ready to begin Camera Match Point placement.

    [View full size image]

    9.

    Right-click the Snaps toggle, and clear the Grid Points selection. Choose Vertex as the only Snap Type. Close the dialog, and click the Snaps toggle to turn it on. Be sure that it is set to 3, the 3D position.

    10.

    In the Render Scene dialog, set the Output Size to 720 x 480. Close the dialog. Hit the hot key M to bring up the Material Editor. Assign the yellow Wireframe material to the box.

    11.

    Choose Create > Helpers. In the panel, open the drop-down menu and select Camera Match. Click the CamPoint button to start laying down match points.

    One by one, click on the vertices of the box and give the points the corresponding names that you see in the background. The points should snap to the corner vertices. When you're done, turn off the Snaps tool.

    12.

    In the Utilities panel, click Camera Match. You should see all of your CameraPoints listed in the CamPoint Info rollout. Select the top point in the list, botB, and then click Assign Position. Click on the botB yellow dot in the background picture. A small red cross appears.

    13.

    Continue with the rest of the points. Notice that the crosses go green when unselected. Click Create Camera, then press the hot key C to see the Camera01 view. The view should be fairly well aligned (Figure 19.33).

    Figure 19.33. The new camera is aligned to the background.

    [View full size image]


    Try a test render. With the Wireframe material on the cube, you can see the exact placement. If you play back the animation, the door swings naturally in the scene.


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