hoknamahn Posted April 27, 2006 Share Posted April 27, 2006 Hi guys. I'm trying to figure out how to calculate a motion vectors in scene where all geometry is static (relatively to the world coordinate system) but the camera is moving. Seems logically to calculate a camera velocity and copy it to all points in my scene. But I see at least one problem - this method can't give me velocities dependent on the distance _from_current_point_ to camera and this method don't take account of the parallax effect. So I try to divide velocities by distance to camera. But I'm not sure is it good idea... Maybe better to use the square of distance? Any suggestions? Quote Link to comment Share on other sites More sharing options...
old school Posted April 28, 2006 Share Posted April 28, 2006 Use CHOPs for an easy solution. Object CHOP > Fetch Postion of Camera | Slope CHOP > Calculates velocity by default Now use the chop() expression to fetch the velocity channels in a Point SOP. Quote Link to comment Share on other sites More sharing options...
old school Posted April 28, 2006 Share Posted April 28, 2006 Oh yeah. You can also figure out the bearing angle and the distance from one object to another to actually figure out the parallax factor adjustment to the velocity. Quote Link to comment Share on other sites More sharing options...
hoknamahn Posted April 28, 2006 Author Share Posted April 28, 2006 Thanks old school. Now I have the idea. The truth is somewhere near but still beyond the bounds of a rich Quote Link to comment Share on other sites More sharing options...
Mario Marengo Posted April 28, 2006 Share Posted April 28, 2006 I could be wrong, but it seems to me that dividing by Z-depth (i.e: point to viewing plane, not point to camera node) should work. But this would only account for translational motion. I have a feeling the trick will stop working as soon as the camera rotates... Quote Link to comment Share on other sites More sharing options...
FrankFirsching Posted April 29, 2006 Share Posted April 29, 2006 Why don't you use the trace-SOP set to Compute Velocities? All you have to do is object merge your scene into a coordinate system, that moves with your camera and apply the trace-SOP. Take a look at the scene I attached. I hope I understood your problem right :-) Unfortunately I may not attach any file to this message. I always get the error: "The requested file upload failed because suitable permissions have not been enabled on the 'uploads' directory. Please contact the board administrator and inform them of this error." So I've put it to the webspace of my universtity: http://www9.informatik.uni-erlangen.de/Per...mputation.hipnc Quote Link to comment Share on other sites More sharing options...
hoknamahn Posted April 29, 2006 Author Share Posted April 29, 2006 Why don't you use the trace-SOP set to Compute Velocities? All you have to do is object merge your scene into a coordinate system, that moves with your camera and apply the trace-SOP. Take a look at the scene I attached. I hope I understood your problem right :-)Unfortunately I may not attach any file to this message. I always get the error: So I've put it to the webspace of my universtity: http://www9.informatik.uni-erlangen.de/Per...mputation.hipnc 27071[/snapback] Arrhh, of course keep it simple! Thanks Quote Link to comment Share on other sites More sharing options...
old school Posted May 2, 2006 Share Posted May 2, 2006 A great example to use something other than "." as the Transform Object in an Object Merge SOP. Thank-you Frank. Quote Link to comment Share on other sites More sharing options...
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