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Thread: Rendering motion vectors out of Lightwave for ReelSmart Motion Blur

  1. #61
    Registered User Skywatcher_NT's Avatar
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    Well, the comp guy tells me the forward and backward vectors don't match. Any thoughts ?

  2. #62
    Here the backward node setup exactly match up with what we got when using negative mblur.

    Look, this is the RSMB result with positive mBlur (original node setup):


    This is what we get when setting negative motion bur (same node setup):


    And this is what we get with positive motion blur and backward node setup:




    Gerardo

  3. #63
    Registered User Skywatcher_NT's Avatar
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    Still having troubles to get the 'backward' vectors.
    What we see here is for a negative motionblur. And yes, the node gives the same result ( thanks for checking again ).
    In fact, if I'm not mistaking you can do that also in comp by making e.g. the X vector ( red ) negative ?
    But when I reverse the scene ( so it plays the anim from 0 to x but then backward ) there's a different outcome for the vectors
    and I don't know if it's possible to get them via nodes this way. In a simple scene I can just mirror the animation ( e.g. 0 becomes 100 and 100 becomes 0 ).
    But for more complex scenes it' s a bit much ...
    Hope there's still a solution !

  4. #64
    Quote Originally Posted by Skywatcher_NT View Post
    Still having troubles to get the 'backward' vectors.
    What we see here is for a negative motionblur. And yes, the node gives the same result ( thanks for checking again ).
    In fact, if I'm not mistaking you can do that also in comp by making e.g. the X vector ( red ) negative ?
    Yes, theoretically is in that way, but in practice people tend to do this in their final compositing project, and there it might not be the same by depending on your CM settings. In such case your comp guy would need to take care about color management to solve first the RSMB pass. So for avoiding unnecessary complexities in comp, I'd recommend solving it with DP Filter in LW beforehand.

    But when I reverse the scene ( so it plays the anim from 0 to x but then backward ) there's a different outcome for the vectors
    and I don't know if it's possible to get them via nodes this way. In a simple scene I can just mirror the animation ( e.g. 0 becomes 100 and 100 becomes 0 ).
    But for more complex scenes it' s a bit much ...
    This might be due to the motion blur could be off-centered.

    Hope there's still a solution !
    If you want to get exactly same results when going forward and backwards you need first to center mblur for each frame. i.e: you might want to try a Shutter Open value of -25% if the Blur Length is set to 50%.



    Gerardo

  5. #65
    An update to this thread with LW 2018:

    Ive just purchased LW2018 and Ive been messing around with instancing and outputing motion buffers.

    I have to say Im impressed and happy with the results so far. LW2018 handles instancing SO much faster and to a much higher instance count on my same old machine. Scenes that were un-workable and slow are totally managable now.

    And outputing the motion vectors is very easy in the render setting tabs. I find I still have to use the same technique inside After Effects to "decode" and use the motion vector output (as in my Youtube video a few posts back).

    But all in all the workflow and results are way better in my opinion. Heres a scene with terrain and one plant/bush that has 3 million instances over a 30 square kilometer area. The motion blur is being done in After Effects using EXtractoR plugin along with Reelsmart Motion Blur.
    Click image for larger version. 

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    Scott

    Cape Town, South Africa
    http://www.youtube.com/user/independentvfx

  6. #66
    gold plated 3D Chrusion's Avatar
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    Scott,

    Thanks for bumping this up to 2018 level. I found it very useful. Now that 2018 has multilayer buffer export to OpenEXR, your vid tutorial plugged right in.

    Put the X instance layer of your EXR on top of the Y instance layer. Set the Layer transfer mode to Add.
    I found the order to be irrelevant. Add is Add no matter which comes first.

    now add a new solid above these two layers. Make the solid R: 0.5 G: 0.5 G: 0 and set this solid to Screen
    This is the layer I don't understand. Why is the 50% yellow offset layer needed? I mean, what does the yellow data do to the vector info contained in the red and green channels? Wait... I'm not sure, but since the blue channel was set to the respective X/Y channels in the Extractor step to make a grayscale image, then that blue "data" captured in both the X and Y layers (shifted to red and green, respectively) must be "cancelled" out by Screening the opposite hue, yellow. Am I close? But why only 50% saturation? Oh, never mind. At 100% saturation (255, 255, 0), the Screen algorithm sees only the full 100% yellow. Interesting. 50% it is, but again, just confirm that yellow is needed to nullify the blue component added when extracting to make each vector a grayscale.

    Ignore all that. After working with 2018, where you can export the XY motion vectors to EXR with X already mapped to R, Y to G, and B = 0, I found that the 50% yellow offset layer isn't needed. When using a separately saved XY exr image (or sequence) directly in RSMB, I get a blur that's twice as much as the extracted and color shifted version. The raw XY exr image does not have a yellow cast to it, so I disabled the yellow screen layer in the extracted version and the blur was exactly the same as the direct XY exr. I'm pretty sure this is because the motion buffer in a multi-layer EXR doesn't have any blue in it to begin with that needs to be cancelled by a yellow offset layer.
    Dean A. Scott, mfa
    Senior 3D Animator and Graphic Design Illustrator, @ Astec, Inc.
    Owner / Lead Artist @ chrusion | FX

  7. #67
    Thanks Chrusion

    I gotta be honest with you - Im not much of a maths guy, so I never really understood what was going on with that funny "50% yellow" screen layer. The only reason I was using it was because the technique had been shown to me that way by a guy from Re:Vision software.

    Im sure there must be a way to just drive motion blur in Reelsmart with the straight motion vectors right out of LW2018 - instead of using the crazy EXtractoR plugin workflow.

    But bottom line - the EXtractoR plugin workflow works and gives the correct result even though its a bit painful and time consuming.
    Scott

    Cape Town, South Africa
    http://www.youtube.com/user/independentvfx

  8. #68
    gold plated 3D Chrusion's Avatar
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    Quote Originally Posted by scott.newman.ct View Post
    Im sure there must be a way to just drive motion blur in Reelsmart with the straight motion vectors right out of LW2018 - instead of using the crazy EXtractoR plugin workflow.
    My apologies for the confusion when I said:
    After working with 2018, where you can export the XY motion vectors to EXR with X already mapped to R, Y to G, and B = 0, I found that the 50% yellow offset layer isn't needed. When using a separately saved XY exr image (or sequence) directly in RSMB...
    I was thinking this was clear in that you CAN use XY Motion data straight out of LW directly in RSMB without having to do the extractor and color shift processing. Just enable Motion in the Buffers tab of Render Globals, then set up the Standard Output to save the Final Render as RGB to desired 24-bit format and the Motion output set to OpenEXR RGBFP. The EXR will have X already mapped to Red and Y to Green. Blue will not be output, so no need to compensate with the 50% yellow screen layer in a separate comp in AE. Simply toss the RGB and EXR sequences in a single comp and add RSMB to RGB layer set to use the EXR layer below it. Max offset = 1, RGB channels = 1, Blur = 2 to 4 as desired. Oh, and set the color management tab in Interpretation properties for the EXR sequence to enable the checkbox for "keep RGB as is (or similar wording)."
    Last edited by Chrusion; 03-16-2018 at 08:29 AM.
    Dean A. Scott, mfa
    Senior 3D Animator and Graphic Design Illustrator, @ Astec, Inc.
    Owner / Lead Artist @ chrusion | FX

  9. #69
    Eat your peas. Greenlaw's Avatar
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    Reviving this old thread because I'm finally trying out LW 2015.3 motion vectors for After Effects and RSMB Pro. I'm using the AE setup from Scott's video, and seeing something odd that I can't figure out.

    My initial tests worked fine. I made a cube that moves in a square pattern, and tumbles along one side of that pattern. I don't have exrTrader at work, so I set up the export using LightWave's native Channel Buffers, and saved out an .exr sequence. In AE, I set the project to 32bpc, assembled the moVec precomp as described in the video, and added an Adjustment layer to the main comp and appled the effect with the suggested settings above the RGB layer. The motion blur looked correct to me. Next, I made a couple of variations of this test and it still looked good.

    Then I tried it on an actual production scene depicting a vehicle zipping wildly through a city environment. In this case, I rendered a 'lightless' version of the scene with the motion vectors and depth channels enabled. I had disabled all ray-tracing effects because I already had an RGB render available and I didn't want to wait all day for buffer channels that didn't need any lighting. I imported the output to AE and setup the moVec precomp. Up to this point, everything looks okay to me.

    Next, I added the Adjustment layer over the RGB render and added the RSMB Vector effect. The motion blur is applied to the scene, I think the directions look good, but he edges of the vehicle are not being blurred.

    At first I thought this was an alpha channel issue but the channel buffer render has both the vehicle and city environment in the same render, so there is no visible alpha.

    Any thoughts? Sorry, I can't show what I'm working on but I was wondering if anybody here has encountered this and knows what I'm doing wrong here.

    One thing I'm noticing is that the RGB values in the moVec precomp sometimes have weird values like 1e+002. That doesn't seem right but I don't see how that effects the vehicle edges either. I can't spend a lot of time on this so fishing for some ideas.

    Thanks in advance for any help.

  10. #70
    Eat your peas. Greenlaw's Avatar
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    One difference between my tests and the production scene is that, in the tests, the objects have no background. I would think this shouldn't be an issue for the production scene though...without an alpha to clip anything, shouldn't the vectors just smear the pixels over the edges.

    The odd pixel value mentioned above has me thinking maybe there are some extreme values going on in this render that prevent the vectors from 'crossing' the edges of the fg object. Does that make sense?

  11. #71
    Eat your peas. Greenlaw's Avatar
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    Oh, I just noticed something else: Occasionally, a foreground environment element passes in front of the vehicle. This object will be blurred correctly against the background but in the region that passes in front of the vehicle, the edge of the FG object is not blurred, just like the edge of the vehicle.

    Something is definitely messed up here.

  12. #72
    Eat your peas. Greenlaw's Avatar
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    I'll see if I can re-create this in a generic example after I get home and upload it here.

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