User manual APPLE SHAKE 4

[. . . ] Under the copyright laws, this manual may not be copied, in whole or in part, without the written consent of Apple. Your rights to the software are governed by the accompanying software license agreement. The Apple logo is a trademark of Apple Computer, Inc. , registered in the U. S. Use of the keyboard Apple logo (Option-Shift-K) for commercial purposes without the prior written consent of Apple may constitute trademark infringement and unfair competition in violation of federal and state laws. [. . . ] This is useful if you plan on redoing the track and you want to clear the old point cloud in preparation for importing a new one. Chapter 18 Compositing With the MultiPlane Node 525 19 Using Masks 19 This chapter describes how you can use masks in Shake to create transparency and to limit the effects of other functions within your node tree. About Masks Masking is the process of using one image to limit another. This typically takes the form of assigning one image to be used as an alpha channel by another. Masking in Shake can also take the form of using one image to limit the effect of a particular node in the node tree. Keying is a process for creating (pulling) a matte, typically using color (green or blue) or brightness (whites or blacks) information from the image to mask that image. Masking is even simpler--it's simply assigning one image to be used as a matte to another image or operation. (For more information on keying, see Chapter 24, "Keying, " on page 681. ) Masks in Shake are extremely flexible, and can be combined in any number of different ways. You can create masks that add to, or subtract from, the existing alpha channel of images anywhere within your node tree. 527 Using Side Input Masks to Limit Effects You can attach a mask to the side input of a node, thereby limiting that node's effect on the input image. In the following screenshots, a mask image (actually an RGrad image node modified by a Move2D node) is used to limit the effect of a Brightness node that's connected to the source image of the car. Source image Mask image By connecting the mask image to the side input of the Brightness node, parts of the source image remain unaffected by the Brightness operation. Masked Brightness node Corresponding node tree Important: The side input is meant to be used with effects nodes only. You can connect an existing mask image to the side input node of any effect node, or you can open an effect node's parameters and create an automatically connected side input mask using the Mask controls. 528 Chapter 19 Using Masks m To attach an image in the node tree to a side input mask: Drag a noodle from an image's output knot, and attach it to a node's side input mask. Drag noodle to side input. . Connected side input mask To create a side input mask: 1 Load the parameters of the node you want to mask into the Parameters tab. 2 Do one of the following: · Click Create to create a new instance of the type of node listed in the pop-up menu to the right. · Choose a different type of node from the Create pop-up menu to the right. A new image node is created, automatically connected to the side input mask. Adding Custom Nodes to the Mask Shape List To add your own nodes to the Mask shape list, add a line similar to the following in a ui. h file: nuiAddMaskCommand("QuickShape", "QuickShape();"); nuiAddMaskCommand("QuickPaint", "QuickPaint(0);"); For more information on ui. h files, see Chapter 14, "Customizing Shake, " on page 355. Chapter 19 Using Masks 529 Parameters Within the Mask Subtree The Mask subtree, located in the top section of any node's Parameters tab, contains the following parameters that let you customize how the input mask image is used: maskChannel Lets you choose which channel to use as the mask. invertMask Lets you invert the mask, reversing its effect on the image. clampMask Turning this parameter on clamps mask image data to a value between 0 and 1. It is important to enable this parameter when using floating point images as masks. enableMask Lets you turn the mask off and on without having to disconnect it. Using Masks to Limit Color Nodes The following example uses images from the tutorial media directory ($HOME/nreal/ Tutorial_Media/Tutorial_Misc/masks) to show how to limit the effects of color nodes using masks. Masking a color-correction node to create a lighting effect: 1 In the Image tab, click the FileIn node, and select the car_bg. jpg, woman_pre. iff, sign_mask2. iff, and car_mask. iff images in the /Tutorial_Misc/masks directory, then click OK. The entire image darkens. 530 Chapter 19 Using Masks 5 To create a mask that gives the appearance of a "spotlight, " do one of the following: · Create an RGrad node (in its own branch), and connect the RGrad output to the M (mask) input on the side of the Brightness node. · In the Brightness parameters, choose RGrad from the Mask pop-up menu. Note: To create the node type already in the Mask shape menu, click Create. For information on the rotoscoping or paint tools and their onscreen controls to draw and edit masks, see Chapter 21, "Paint, " on page 579. An RGrad is connected as the mask input for the Brightness node, and the masked portion of the image is darkened. 6 In the Node View, select the RGrad node, click the Transform tab, then click the CornerPin node. 7 Using the onscreen controls and the following image as a reference, adjust the RGrad image to put the circle in perspective. Chapter 19 Using Masks 531 For more information on transforming with onscreen controls, see Chapter 26, "Transformations, Motion Blur, and AutoAlign, " on page 763. 8 To invert the mask, open the Mask subtree in the Brightness node, and enable invertMask. The mask is inverted, and the masked portion of the image is lightened. Don't Use Mask Inputs With Layer Nodes Mask inputs are useful for color corrections and transforms. As the following example shows, even with color and transform nodes, masks should be used with caution. 532 Chapter 19 Using Masks Masking Concatenating Nodes It is never a good idea to use side input masking with multiple successive concatenating nodes because doing so breaks the concatenation. Breaking node concatenation with side input masks--don't try this at home: 1 Select the Brightness node and apply a Color­Mult node. 2 In the Color controls of the Mult node parameters, set the Color to blue. [. . . ] Animates a rotation from 0 degrees at frame 1 to 360 degrees at frame 11. Notice only up to frame 10 is rendered, hopefully giving a smooth loop. Sets motion blur to half quality. Creates a temporary curve named A. Uses the time variable, placing it in quotes to multiply it by itself. [. . . ]