![\"Smoke](\"http:\/\/www.premiumbeat.com\/blog\/wp-content\/uploads\/2012\/07\/Header.jpg\")
<\/a><\/strong><\/p>\n Motion vectors<\/strong> are a magical render pass that you can create in 3D applications like Maya, Cinema4D, and 3DS MAX<\/strong>. \u00a0When working with CGI rendered elements in post production, it is often advantages to render out Motion Vector Passes<\/strong> so that you can add motion blur to the 3D elements in post. This saves you tons of time in rendering in the 3D application. \u00a0It also gives you complete flexibility in matching the blur with other elements throughout the composite. \u00a0OpenEXR<\/strong> is the most commonly used format for these CGI renders due to it’s high bit depth and High Dynamic Range (HDR)<\/strong> abilities.<\/p>\n Autodesk Smoke 2013<\/strong> has several nodes in ConnectFX<\/strong> that can process the motion vector information. Motion Blur Node, Timewarp Node, and Pixel Spread<\/strong>. Smoke also has the Motion Analysis Node<\/strong> that will create motion vectors from movement in a clip.<\/p>\n After importing the OpenEXR,\u00a0the 3D image is represented in Red, Yellow and Green<\/strong> colors to the viewer as a clip. The actual motion data is in the RGB color channels. \u00a0Red and Green Channels represent the X and Y movement of a pixel and the Blue channel can be use to set the magnitude of the motion. \u00a0Black in the image shows that there is no motion in those pixels.<\/p>\n There are 2 directions for Motion Vectors… Forward Vectors (Next Frame) and Backwards Vectors (Previous Frame)<\/strong>. Forward Vectors are the more common and if you don’t have any information on the vectors, you can assume that it’s forward. \u00a0 There are also 2 formats that vector information can be stored. Absolute Vectors and Normalized Vectors<\/strong>. \u00a0Absolute Motion Vectors is the format that all tools that support motion vectors inside of \u00a0Smoke are expecting and generating. \u00a0The Motion Analysis Node will generate Absolute Vectors. \u00a0Normalized Vectors can be used and converted in the Motion Blur Node.<\/p>\n How do you know what format you are dealing with? If the bit depth of the clip is\u00a08,10 or 12-bit, it is Normalized. \u00a0If it’s float or half-float (16 or 32-bit), then a color histogram is your best friend. If the file only contains colour information between 0 and 1 then it’s Normalized, \u00a0if there any negative values present it’s Absolute.<\/em><\/p>\n This node is very simple. The UI contains one pop up button selection for the quality of the analysis. Full resolution will give you the best results and also take the most time rendering.<\/p>\n Simply connect a clip to the front input and the node will produce both front and backwards vectors. \u00a0It may be a good idea to cache and render this branch of the schematic as a CFX clip. This will speed up renderings down the line.<\/p>\n [Click Image for Larger View] The Motion Blur Node accepts only a forward vector. The Vector Input Type Menu is where you select Normalized or Absolute Vectors. If the Blue Channel has magnitude data you can enable the button to take\u00a0advantage\u00a0of that in the blur. \u00a0You can also activate the Black as No Movement<\/strong> button and threshold value to take the near-black pixels into account for the motion blur.<\/p>\n Activate the Show Icons<\/strong> button to see the movement of the Motion Vectors as colored arrows. \u00a0You can adjust the size and amount of the display with the grid and scale values. This is only to help you visualize how the motion vectors are being evaluated. It has no effect on the result.<\/p>\n You can choose Trails or Samples<\/strong> for the blur type. You can adjust the look of the blur with the Amount, Softness and Balance<\/strong> values.<\/p>\n<\/a><\/p>\n<\/a><\/p>\nSmoke’s Motion Analysis Node:<\/h3>\n
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\n<\/a><\/p>\n<\/a><\/p>\nSmoke’s Motion Blur Node:<\/h2>\n
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