# sourceTileRect(_:sourceImageIndex:sourceImages:destinationTileRect:destinationImage:pluginState:at:) Calculate the input rectangle needed for the given image input and the output tile to be rendered. ``` func sourceTileRect(_ sourceTileRect: UnsafeMutablePointer, sourceImageIndex: Int, sourceImages: [FxImageTile], destinationTileRect: FxRect, destinationImage: FxImageTile, pluginState: Data?, at renderTime: CMTime) throws ``` ## Parameters `sourceTileRect` The bounds of input tile for this input that will be needed to render the output tile. This method must calculate this value. `sourceImageIndex` The index of the input image for which the tile bounds have been requested. This index matches the order of images in the `inputImages` array below. `sourceImages` An `NSArray` of image tiles representing the input images. This image will not yet contain any pixel data, just the image bounds, pixel transforms, and other data describing the image. `destinationTileRect` The bounds of the output tile, given to you by the host application. `destinationImage` The output image. This image will not yet contain any pixel data, just the image bounds and other data about the output image. `pluginState` The NSData returned from your plug-in’s [`pluginState(_:at:quality:)`](/documentation/professional_video_applications/FxTileableEffect/pluginState(_:at:quality:)) method. `renderTime` The rational time at which the output will be rendered. ## Discussion This method is called for each image input your plug-in has requested. Use the passed-in information to calculate the portion of the current input image that you’ll need to render the output tile that will be rendered next. --- Copyright © 2026 Apple Inc. All rights reserved. | [Terms of Use](https://www.apple.com/legal/internet-services/terms/site.html) | [Privacy Policy](https://www.apple.com/privacy/privacy-policy)