Differences
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bitmap_display [2014/11/19] |
bitmap_display [2020/08/14] (current) |
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| + | ====== Image File Support in Rhino 5====== | ||
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| + | Rhino 5 supports the attachment of image files in the [[http:// | ||
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| + | **Rhino works best with image files that are "power of 2" in size.** | ||
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| + | //This is because Rhino displays image files as textures - always.// | ||
| + | ===== Images stored as textures ===== | ||
| + | To display a file as a texture, Rhino uses OpenGL to //texture map// a polygon or polygon mesh. This is important information for many reasons: | ||
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| + | - OpenGL stores textures in GPU memory. | ||
| + | - Because of #1, OpenGL implementations have hardware requirements (limitations) on how big a texture can physically be. | ||
| + | - Because of #2, there is no //standard maximum// defined size for a texture. It's based on your video card and drivers. | ||
| + | - Because of #3, Rhino can't just use any file at any resolution and assume it's going to work. | ||
| + | - Because of #4, if Rhino encounters an image file that does not meet your video hardware capabilities, | ||
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| + | **//It is not a requirement for Rhino 5 that image files be exactly sized to a power of 2.//** | ||
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| + | But, the internal representation in Rhino (and thus for OpenGL) __is__ a power of 2. | ||
| + | In other words, you can throw any file or texture at Rhino 5 and it will make sure it works on most video hardware. | ||
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| + | ===== Adjusting for the power of 2 ===== | ||
| + | So how does it make it work if the image is not a power of 2? | ||
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| + | //**If Rhino needs to resize an image, it will resize it to the next highest power of 2 that is greater than the current dimensions but less than or equal to the maximum dimensions supported by the current hardware.**// | ||
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| + | Here are a few examples to illustrate this. | ||
| + | //Assume the current hardware' | ||
| + | If Rhino sees a file with dimensions: | ||
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| + | * 256 x 256 - Rhino will do nothing, perfect powers of 2. | ||
| + | * 1024 x 1024 - Rhino will do nothing, perfect powers of 2. | ||
| + | * 1024 x 256 - Again, Rhino will do nothing, perfect powers of 2. | ||
| + | * 127 x 127 - Rhino will resize the image to 128 x 128, next highest value that is a power of 2 and greater than the current dimensions. | ||
| + | * 129 x 129 - Rhino will resize the image to 256 x 256, again, the next highest value that is a power of 2 and greater than the current dimensions. | ||
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| + | Rhino will never // | ||
| + | * 9000 x 6000 - Rhino will resize (downsize) the image to 8192 x 8192. 9000 exceeds the 8192 maximum limitation and 6000 isn't a power of 2. The next available power of 2 is 8192. | ||
| + | * 9000 x 9000 - Rhino will resize (downsize) the image to 8192 x 8192. Both dimensions exceed hardware limitations and are adjusted to the maximum limits. | ||
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| + | ===== Pixelization ===== | ||
| + | When Rhino does resize the image, it does not use any kind of sampling or bi-linear filtering. It is a //straight linear stretch or shrink// | ||
| + | So, if the difference between original dimensions and adjusted dimensions is greater, the results look worse. | ||
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| + | Take the 129 x 129 example above. Rhino basically has to double the size of the image resulting in every pixel now being a 2 x 2 block in the final result. | ||
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| + | **This is the major cause of pixelization in the display of the attached image.** | ||
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| + | But, the results can even look worse if it tried resizing to 128 x 128. Banding can often occur because entire rows or columns of pixels have been removed. | ||
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| + | //Rhino will not downsize anything unless it absolutely has to due to hardware limitations.// | ||
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| + | ===== Basic recommendation===== | ||
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| + | //**Always keep images as close to values that are just less than powers of 2 as possible. And if you can, try to make them powers of 2**.// | ||
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| + | Given today' | ||
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| + | //Making them any larger is a waste of time, space, and will cause Rhino to throw out a lot of good pixel information.// | ||
