Results 1 to 14 of 14

Thread: Speed up your renders with motion blur... a LOT

  1. #1
    LW Oldtimer KeystoneMike's Avatar
    Join Date
    Aug 2003
    Location
    California
    Posts
    30

    Speed up your renders with motion blur... a LOT

    If you've noticed render times with motion blur on seem really long, especially with polygon heavy scenes here's something you can do that should help speed things up:
    Open the object properties panel. For every object and null in your scene turn OFF the Subdivision and Bones modifiers in the Primitive/Geometry tab if that object does not contain either. Obviously if your object has bones or subpatches you'll need to leave these on for them but for everything else, turn those two modifiers OFF. Give it a try and see what happens.

  2. #2
    Electron wrangler jwiede's Avatar
    Join Date
    Aug 2007
    Location
    San Jose, CA
    Posts
    7,226
    If the modifiers aren't "doing anything" for the object (no active sub-d's in case of subdivision, no bones associated in case of bones), they shouldn't incur any render cost in any of the stages. If they're incurring processing cost regardless of whether they're even being used, that's actually a significant bug, and needs to be reported ASAP.

    Are you seeing this generally? Or only in specific object configuration or more complex scenes? Are object replacement or custom object plugins applied to the object(s) in question?

    LW has all the info needed to determine when to turn them on (sub-d's active, bone association with object mesh), so they probably shouldn't be "on" automatically in any case. I guess I can imagine how there might be odd compatibility cases where that "begin enabled" behavior is needed, though that behavior (clear-to-classic-modifiers-on) should likely have a pref control as well.

    Regardless, at the start of VPR/render processing, LW should have no difficulty detecting that despite being "switched on" those modifiers never get "used" (because no sub-d activation occurs, nor are bones bound).

    If that detect-at-render behavior won't work with object replacement or similar custom object plugins, disable it upon those choices being activated (those aren't active by default, so are fine as "disabling triggers"). None of that should block "confirm-modifier-use-at-render-else-disable" by default, though.
    Last edited by jwiede; 04-13-2020 at 01:35 AM.
    John W.
    LW2015.3UB/2019.1.5 on MacPro(12C/24T/10.13.6),64GB RAM, NV 980ti

  3. #3
    LW Oldtimer KeystoneMike's Avatar
    Join Date
    Aug 2003
    Location
    California
    Posts
    30
    Bug reports related to this have been in the system for at least two years. I'm pretty sure these modifiers are on by default for the same reason an empty scene comes with a camera and light... so that things will just 'work'. It's up to NewTek to figure out what's going on. I'm just providing a possible solution for those who see extremely long render times. I would say you're probably only likely to notice it in really heavy scenes. My scene in particular has 19 objects, 2 bones, just over 5 million points and just under 5 million polygons. Some bits are subpatched. If I do a render at 1280x720 with the Subpatch and Bones modifiers on for everything it takes about 1 hour, 45 minutes with my current settings. If I turn those modifiers off for the objects that don't require them to be on my render time drops to just over 4 minutes. This is with default motion blur settings.

  4. #4
    Post-LW Engineer Jarno's Avatar
    Join Date
    Aug 2003
    Location
    New Zealand
    Posts
    626
    What it basically comes down to is that there is no way for the renderer to know that an enabled modifier will or will not do anything, without actually evaluating the modifier. So for the motion blur it assumes that if there is an enabled modifier, then the mesh will be deforming and it will compute the deformation for each motion blur slice.

    This is an area we are trying to be better at. Meanwhile, if you don't need it on, turn it off.

    ---JvdL---

  5. #5

    also you should use DPont Vector Blur on top om LightWave moblur.

    you'll get half render time, and basically same quality.
    LW vidz   DPont donate   LW Facebook   IKBooster   My vidz

  6. #6
    Nice find and share.
    Most appreciated.
    Robert Wilson
    i-7-4770k @3.5ghz, Titan, GTX 1660 Ti, et al

  7. #7
    Registered User
    Join Date
    Jan 2011
    Location
    Seattle
    Posts
    448
    Wow! This is major. Thanks for the heads up.

  8. #8
    Eat your peas. Greenlaw's Avatar
    Join Date
    Jul 2003
    Location
    Los Angeles
    Posts
    7,290
    I don't know if this is related but, many years ago, we found that if the Display Sub-D and Render Sub-D levels didn't match, the 'freezing' stage could place a huge hit on render times.

    As a matter of fact, a button was added to our render submit tool to match the values in the submitted file if they didn't. If I remember correctly, the script could do this for some or all objects in the scene that didn't match. This also left alone the file the artist was working in so it didn't affect UI performance.

    At home, out of years of habit, I do this manually before submitting a render.

    I wish similar 'render optimization' options could be built-into Layout.

  9. #9
    Super Member
    Join Date
    Aug 2016
    Location
    a place
    Posts
    2,484
    could a scene optimization script be made to run through everything prior to rendering? sort of thing oliver would
    have done in od tools if still with us.

  10. #10
    Super Member
    Join Date
    Aug 2016
    Location
    a place
    Posts
    2,484
    Quote Originally Posted by Jarno View Post
    What it basically comes down to is that there is no way for the renderer to know that an enabled modifier will or will not do anything, without actually evaluating the modifier. So for the motion blur it assumes that if there is an enabled modifier, then the mesh will be deforming and it will compute the deformation for each motion blur slice.

    This is an area we are trying to be better at. Meanwhile, if you don't need it on, turn it off.

    ---JvdL---
    im trying to lose weight. why not commit to a fix?

  11. #11
    Quote Originally Posted by gar26lw View Post
    could a scene optimization script be made to run through everything prior to rendering? sort of thing oliver would
    have done in od tools if still with us.
    could be.

    LW vidz   DPont donate   LW Facebook   IKBooster   My vidz

  12. #12
    LW Oldtimer KeystoneMike's Avatar
    Join Date
    Aug 2003
    Location
    California
    Posts
    30
    Quote Originally Posted by gar26lw View Post
    could a scene optimization script be made to run through everything prior to rendering? sort of thing oliver would
    have done in od tools if still with us.
    OD_Tools has a Server Change Status tool. (OD_2018 Tab under the Servers section) It works on multiple items. Select Mesh Modifier as the Handler Type, under the Adjust pull-down select <<< ALL >>> (or whatever you want to set) and set the state to Disable. Easy Peasy.

  13. #13

    Quote Originally Posted by KeystoneMike View Post
    ...If I do a render at 1280x720 with the Subpatch and Bones modifiers on for everything it takes about 1 hour, 45 minutes...
    If I turn those modifiers off for the objects that don't require them to be on my render time drops to just over 4 minutes. This is with default motion blur settings.
    dang, need to write this down (!)



    OD_Tools has a Server Change Status tool. (OD_2018 Tab under the Servers section) It works on multiple items.
    Select Mesh Modifier as the Handler Type, under the Adjust pull-down select <<< ALL >>> (or whatever you want to set) and set the state to Disable. Easy Peasy.
    LW vidz   DPont donate   LW Facebook   IKBooster   My vidz

  14. #14
    Registered User
    Join Date
    Sep 2015
    Location
    Sweden
    Posts
    830
    Quote Originally Posted by gar26lw View Post
    im trying to lose weight. why not commit to a fix?
    And you wonder why the developers Tend not to participate in this forum...

Tags for this Thread

Bookmarks

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •