Hans Peter Posted February 10, 2017 Share Posted February 10, 2017 Hi there, I'm having a hard time exporting some motion vectors out of Mantra. I used a method that was described in this forum. Two get blur nodes, one set to 0 and the other one to 1. Subtracted them and piped into a custom direction vector attribute which I used to render out an image plane in Mantra. Unfortunately I'm not getting any motion vector in the exr file. The image plane is black and when trying to use it with a vector blur in Nuke or a velocity blur in Houdini's comp area nothing happens. Quote Link to comment Share on other sites More sharing options...
Jero3d Posted February 10, 2017 Share Posted February 10, 2017 Could you post the hip file? It sounds like the motion vector pass isn't being created. I would double check that the attribute you are exporting is set to be a vector, and that the image plane has the correct attribute name and data type. Also make sure you have the setup on the shaders that your geometry is using. Use the IPR to see if there's anything there. I'm guessing you got the setup from the thread below, but there are 2 of them. I have used Matt's method and it works every time! I would give that a try or you can post a hip file so it's easier to pinpoint the issue. All I said above are just guesses, I can't be sure without looking at it This is the post with the working setup: Quote Link to comment Share on other sites More sharing options...
Hans Peter Posted February 10, 2017 Author Share Posted February 10, 2017 So here is a simplified version. Maybe you can get this to work. motionvector.hiplc Quote Link to comment Share on other sites More sharing options...
Skybar Posted February 10, 2017 Share Posted February 10, 2017 I think you have to enable motion blur on your mantra rop, but disable the image blur, for motion vectors to work. If you have done that already I don't know. Quote Link to comment Share on other sites More sharing options...
Hans Peter Posted February 10, 2017 Author Share Posted February 10, 2017 I've done it now but it still isn't working Quote Link to comment Share on other sites More sharing options...
Jero3d Posted February 10, 2017 Share Posted February 10, 2017 I changed the way you were exporting the motion blur to the setup I mentioned. Also you have to enable Allow Motion Blur in Mantra, and to use the velocity of your object I enabled Geometry Velocity Blur under the Sampling tab of the geometry object. (If you only want to use transformation blur then you can increase the xform samples to 2 in Mantra). Finally you also have to assign the material to the object. motionvector_working.hipnc Quote Link to comment Share on other sites More sharing options...
Hans Peter Posted February 10, 2017 Author Share Posted February 10, 2017 Thanks. It works in this file. Tried to port this to my main file but getting some error messages Quote Link to comment Share on other sites More sharing options...
Jero3d Posted February 10, 2017 Share Posted February 10, 2017 Make sure you copied the whole setup inside the Mantra Surface, including the null node that is renaming the variable to ndcvec. If you didn't copy the null node, you can also change the last line of the snippet to diff *= res; That is provided you didn't add any nodes after the subtract. If you did, just replace diff with the data name that is being output from the node that is being connected into the snippet. Quote Link to comment Share on other sites More sharing options...
Hans Peter Posted February 10, 2017 Author Share Posted February 10, 2017 I did copy the null node too but the error message remains Quote Link to comment Share on other sites More sharing options...
Hans Peter Posted February 10, 2017 Author Share Posted February 10, 2017 It seems to be working now. 1 Quote Link to comment Share on other sites More sharing options...
Hans Peter Posted February 10, 2017 Author Share Posted February 10, 2017 (edited) lol, I give up. Mantra isn't crashing but the motion vector I'm getting is rather rubbish. COULD be a little easier to get the motion pass.. Edited February 10, 2017 by Heraklit Quote Link to comment Share on other sites More sharing options...
Hans Peter Posted February 10, 2017 Author Share Posted February 10, 2017 lol, I give up. Mantra isn't crashing but the motion vector I'm getting is rather ribbish. COULD be a little easier to get the motion pass.. Quote Link to comment Share on other sites More sharing options...
Hans Peter Posted February 11, 2017 Author Share Posted February 11, 2017 (edited) Another question: how would you give out a velocity aov? Same technique? Following the houdini help section the velblur node needs the velocity from the velocity plane. Is this the motion vector? Because I can't get any result with the outputted motion vector. Edited February 11, 2017 by Heraklit Quote Link to comment Share on other sites More sharing options...
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