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--- tutorials:matchmoving [2008/06/22 18:36]
sympodius
+++ tutorials:matchmoving [2010/06/18 05:16] (current)
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 This last technique is the one we plan to use in our film and is the one we will attempt to demonstrate in this tutorial. We're going to use a fairly simple example to demonstrate the technique as most of the things we are planning do not involve especially complex interactions.
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 {{tutorials:blendersetrenderdirectory.png|Blender Set Render Directory}}
-We have noticed that Blender will occasionally output blank frames at the end of a clip instead of the ones from the source video. You can see this before rendering the output by playing the file in Blender's preview first. To do this, change the view type of the Video Sequence Editor to “Image Preview” instead of “Sequence.”
+We have noticed that Blender will occasionally output blank frames at the end of a clip instead of the ones from the source video. This appears to me due to some sort of memory issue. We've found the best way to deal with it is to change the start frame to the number of the first blank Targa file and then re-render the blank frames. If it continues to output blank frames, try restarting your computer before the re-render. If that fails, you will have to remove the offending frames. The simplest solution to this is to cut off the frames that are causing the problems. To do this, go back into the “Sequence” view and right click on the right arrow of the video strip and drag it left to a point where you expect the video to be fine. Once no black frames show up and you are happy with the video, you can see how many frames the video strip has become (it's shown on the far right on the video strip) and change the length of the output video accordingly. In our case, we reduced our video length to 715 frames.
-{{tutorials:blendervseimagepreview.png|Blender Video Sequence Editor Image Preview}}
-You may have to zoom out a little to see the video properly (use the mouse wheel). Now just hit “Alt+A” while your mouse is over the Image Preview window to play through the source video. The simplest solution to this is to cut off the frames that are causing the problems. To do this, go back into the “Sequence” view and right click on the right arrow of the video strip and drag it left to a point where you expect the video to be fine. You can test your estimation by previewing the video again. Once no black frames show up and you are happy with the video, you can see how many frames the video strip has become (it's shown on the far right on the video strip) and change the length of the output video accordingly. In our case, we reduced our video length to 715 frames.
 {{tutorials:blendervsenewframelength.png|Blender Video Sequence Editor New Frame Length on Strip}}
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 Make sure that you save the Blender file somewhere as we will be using it again later.
-The next step is to take the Targa files and put them into a Camera Motion Tracking software package. Although there is a discontinued program called “Icarus” that is somewhat popular in the Blender community, we decided to use one called “Voodoo” because it seems easier to use and is still under development (which means it will continue to improve). Both programs are free to use, but Icarus can only be used for educational purposes. Voodoo can at least be used to make movies you might plan on making money from. Sadly, neither program is open source, but we live in hope.
+The next step is to take the Targa files and put them into a Camera Motion Tracking software package. Although there is a discontinued program called “Icarus” that is somewhat popular in the Blender community, we decided to use one called “Voodoo” because it seems easier to use. Both programs are free to use, but Icarus can only be used for educational purposes, while Voodoo can be used for all non-commercial purposes. Sadly, neither program is open source, but we live in hope.
+When we originally wrote this tutorial, Voodoo was available to be used for commercial purposes as well. However, one of our readers has now informed us that this policy has changed. We find this rather sad news as we no longer know of a good, free camera motion tracking package that can be used for commercial purposes. There is always a lot of talk in the community about including Camera Motion Tracking as a feature of Blender, but as far as we know no one has ever attempted this. In any case, we thank Robert Hamilton for informing us of the change in Voodoo's terms and conditions.
 You can get Voodoo from, http://www.digilab.uni-hannover.de/download.html
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 <object width="425" height="350"><param name="movie" value="http://www.youtube.com/v/hKIpjz0n2uw"></param><embed src="http://www.youtube.com/v/hKIpjz0n2uw" type="application/x-shockwave-flash" width="425" height="350"></embed></object>
 </html>
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 The first issue (which you may have realised for your selves) with our shot is that there were no moving elements. Match moving largely relies on the idea that there are a lot of elements in the shot that are stationary and that it is mainly the camera that is moving. However, you can still include moving things in the shot (like actors and such), but you will probably get results that are not quite as good. Also, if you choose not to use a tripod shot and use a free moving camera, you may find the results will be way off. Some of the tests we did with this weren't very good. Our recommendation for good results is to limit the number of active elements in the original shot and try to stick to tripod-based panning.
-You may also find that the perspective in Blender does not line up with the original shot. This usually stems from keeping the object at an incorrect distance from the camera. Generally, moving the object to different distances from the camera and resizing it to compensate can solve this problem. However, you might find that adjusting the focal length settings in Voodoo can also improve these perspective issues.
+You may also find that the perspective in Blender does not line up with the original shot. This usually stems from keeping the object at an incorrect distance from the camera. Generally, moving the object to different distances from the camera and resizing it to compensate can solve this problem. However, you might find that adjusting the focal length settings in Voodoo can also improve these perspective issues. The ideal situation is for the original camera, the voodoo settings and the Blender virtual camera to all have exactly the same settings. If you can achieve this then you will get the best results.
 This tutorial has not covered shadows, reflections, lighting and when real elements move in front of the virtual elements. We hope to cover all of these in a later tutorial.