Image Authoring and rendering texture resolution

Rendering textures onto vignette objects in Image Authoring and Image Rendering depends on an accurate relationship between the resolution of the repeatable texture and the object's size. If the texture resolution and the object size are set accurately, the renderer ensures a perfect match.

Determine the texture resolution: The texture resolution is expressed in pixels per inch (ppi). It describes the relationship between the texture image and the physical sample of the material (fabric, wallpaper, and so on).

You can determine the texture resolution by measuring the distance (in pixels) between two arbitrary points in the image. Then, measure the corresponding distance (in inches) on the physical sample, and divide:

res = imageDistance / physicalDistance

The distance could be the width or height of the entire repeatable area. For example, if the repeatable swatch image is 542 pixels wide, and the measured, physical width of the visible repeatable texture is 17.12 inches, the texture resolution is 542/17.12 = 31.66 ppi.

Alternatively, if the material was scanned on a flatbed scanner, the texture resolution corresponds directly to the scan resolution. Make sure to account for any scaling of the image that can change image size and resolution. For example, a fabric sample was scanned at 72 dpi, and the raw image is cropped to a full repeat, making the image 1773 x 842 pixels. To save space, the image then is scaled to 500 pixels width (the height is now 237 pixels). The new resolution is adjusted by the scale factor:

newRes = oldRes * newWidth / oldWidth

Example: 72 ppi * 500 / 1773 = 20.305 ppi.

Set the object size: When authoring objects with the Vignette Authoring Tool in IA for applying textures, it is necessary to specify an appropriate object size.

3D scenes: Set the scale for the entire scene before importing the 3D data into the object hierarchy. On the 3D Modeling Page, select the Picking Tool, select an edge with a known length (in inches). Type that measurement in the Selected Length field and press Enter. Select some other edges in the scene and verify that the measurements displayed in Current Length are reasonable. Do this scaling operation after the camera is finalized and at least some model surfaces created and tested. But, do it before importing the final 3D model data with the 3D Import Model Tool on the Object page. Do this step only once. However, if either the camera or the scale changes on the 3D model page, it's necessary to reimport the entire hierarchy.

2D scenes: A good sense of the actual size of the objects in the scene is required for accurate authoring. Use the Edit Model Tool to assign a width and a height (in inches) to all Flat Objects, Walls, and Cabinets.

Flowline objects: For both 2D and 3D scenes, set the Overall Size (in inches) of a part (object) in the Texture Tool on the Flowline Page. The "Flow across Parts" mechanism helps fine-tune the resolution to match adjacent parts.

Rendering: Image Authoring and the Image Rendering server applies the repeatable texture to the object as follows (much simplified): (1) The texture is first scaled to an optimal resolution for th target object/part (you can see that resolution on the Texture tab in the object's Properties in the VAT). (2) The texture is repeated at that resolution to cover the total area equivalent to the object size. (3) the texture is then transformed to match the shape of the target object.

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