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  • xpresso nodes not displaying numerical results

    Posted by Keith Slawinski on October 19, 2013 at 2:56 pm

    Running c4d r15.037 Studio on PC.
    I have been flying blind with xpresso lately. Nodes are not displaying results (siting specifically the constant, spy, and result node). The constant node, for example, displays “Real ()” for ANY user defined data (data type updates fine). Restarting and opening new scenes yields nothing.
    I remember Being able to display results at one point, but I am still new. Note, that I recently accepted a notified software update although I thought it was just a help-doc update at the time. Please let me know if you can provide insight. I have broken xpresso chains and no way to troubleshoot them.

    Steve Bentley replied 10 months, 2 weeks ago 5 Members · 5 Replies
  • 5 Replies
  • David Cabestany

    May 1, 2015 at 7:58 pm

    Did you ever figure this out? My nodes were working fine last night but today it’s the same thing, both the spy and result nodes. Some others show as undefined, even though I haven’t deleted anything from my scene.


  • Adam Nieman

    February 23, 2022 at 2:18 pm

    For anyone coming across this problem, I have found it usually happens when I have a Python script within the xpresso, which is not working. It is really hard to debug Python code in xpresso, I find, so it might not be obvious that it’s Python that’s the problem. I wish both xpresso and Python would provide better error messages.

  • Steve Bentley

    February 27, 2022 at 12:23 am

    This could be a couple of things:

    The usual suspect is that the viewport isn’t visible. I have my xpresso window tabbed up along with the viewport and picture viewer and the material nodes window and often I will pop in to the xpresso tab and wonder why it won’t update – because it’s taken over the entire screen with the viewport hidden in “behind”. The viewport MUST be visible for xpresso to update.

    It could also be an ordering thing. The order stuff happens, both in the xpresso window (left to right) and the object manager (top to bottom) matters. If something has to be calculated first before doing something else, often it has to be left or below that second thing.

    It could be that the data type is wrong. In the Spy or Result nodes make sure that the data type you are wanting to read is what that node is set to. And make sure that the data type is appropriate. This is often difficult as C4D seems to care sometimes (like Frames being Integers instead of Reals) and sometimes it doesn’t (Bools instead of 0’s or 1’s).

    The final trick to try is to make sure you are really on frame zero and then stuff can calculate as it evolves. Just hitting rewind doesn’t always do it – often you have to hit rewind twice or, once at frame 0, advance to frame 1, then rewind again. C4D has a terrible habit of not clearing its own cache when a calculation needs to start again.

  • Tom Morton

    September 4, 2023 at 1:28 pm

    Arrived here, second result on google.

    Using R20 and getting the same problem, where Result and Spy nodes are blank. Have unlinked them, duplicated them, deleted them, refreshed them, connected to nodes which are working, but no luck as yet.

    Only thing I can think of is that everything was working fine, I did a test render, one Xpresso animated part wasn’t working, dived into the editor to find out why and result nodes are obstinately staying blank.

  • Steve Bentley

    September 4, 2023 at 2:23 pm

    Is your viewport open? (the 1 or 4 views where you see your scene). xpresso (and some 3rd party IPR render windows), can only update when the viewport is open and can update on screen.
    So if you have opened the xpresso editor and it has covered your viewports or you have made it a tab and that tab now has focus, xpresso can’t update.

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