Download

Online

Gallery

Blog

  Index  | Recent Threads  | List Attachments  | Search
 Welcome Guest  |  Register  |  Login
Login Name  Password
 

Sweet Home 3D Forum



No member browsing this thread
Thread Status: Active
Total posts in this thread: 2
[ Jump to Last Post ]
Post new Thread
Author
Previous Thread This topic has been viewed 4962 times and has 1 reply Next Thread
mazoola
Advanced Member
Member's Avatar

USA
Joined: Mar 25, 2015
Post Count: 153
Status: Offline
Reply to this Post  Reply with Quote 
Einstein would say this is insane...

...but I've been doing the same thing over and over again -- and getting different results.

@Emmanuel -

I initially thought this was a new problem with 5.2, but I've pretty much replicated it in 4.6 and 5.0. (I say 'pretty much' because, as you'll see, it's difficult to reproduce exactly.) I'm including only a single example.

The following animated GIF compiles seven sequential renders. To create them, I opened SH3D, loaded a scene, opened the render window, rendered frame 1 using the default settings for Q4, saved frame 1, clicked 'Create' and rendered frame 2, saved frame 2, and so on. In other words, I changed nothing between renders: After loading the plan and opening the 3D render wndow, all I did was alternate between 'Create' and 'Save.'

As you can see, highlights and refracted images in the wine glasses are not consistent from one frame to the next; in fact, no two frames are the same.

Initially I discovered this by noting how repeated renders of a scene containing a problematic Sketchup-generated model weren't identical -- and, admittedly, this, too, could be related to Sketchup's quirky insistence on creating double-faced surfaces, as the table and chairs and place settings are all from 3DWarehouse. However, I have gone to great lengths to ensure not only are both faces of a surface mapped with identical colors or textures, but that all triangles for a given face are oriented correctly.

Note: Sketchup differentiates between the two faces making up a surface by initially shading one white and the other blue. Obviously, once a color or texture has been applied, the default shades are over-written. However, if one selects 'monochrome' as the surface style, Sketchup reverts to the default white/blue rendition, allowing one to select and reverse any unaligned triangles. This is an incredibly annoying task, BTW, but I was trying to eliminate unpredictable surface normals as a possible cause. While my next step will be to try to duplicate using only stock SH3D objects, I would still expect a broken Sketchup model at least to break identically in identical renders.

While I can think of several potential causes for such behavior, I've not yet come up to speed enough on ray-tracing, Java, or ray-tracing in Java to find the culprit. My SWAGs:

  • SunFlow render object isn't being destroyed and recreated properly between renders.
  • A 'semi-static' (i.e., supposedly unchanged from render to render) SH3D variable later passed to SunFlow is being incremented or otherwise modified between renders.
  • A SunFlow option enabling some randomizable feature -- jitter, for instance -- is being set or defaults to 'on.'
  • SH3D is somehow exporting dissimilar scenes to SunFlow, thanks to some varying input (current time-of-day, perhaps)
  • A mis-cast function call is erroneously changing a variale passed to SunFlow.

Unfortunately, so far I've not been able to identify exactly what one would change in the SunFlow scene description to cause such variation. At first glance, it looks as if it might be something having to do with depth of refraction, but that's far from certain.

As usual, I'm raising this issue not because it represents a significant problem with SH3D -- although it could certainly cause someone, ahem, to spend an inordinate amount of time trying to figure out why presumably identical renders aren't really identical. Rather, I bring it to your attention on the off-chance the code glitch responsible for this unintended behavior might cause other, less innocuous problems under other circumstances.

Maz
[Mar 9, 2016, 7:47:17 PM] Show Printable Version of Post    View Member Profile    Send Private Message [Link] Report threatening or abusive post: please login first  Go to top 
mazoola
Advanced Member
Member's Avatar

USA
Joined: Mar 25, 2015
Post Count: 153
Status: Offline
Reply to this Post  Reply with Quote 
Re: Einstein would say this is insane...

And...

...the problem seems linked to Sketchup-created objects.

I created a comparable scene using only standard SH3D furniture items and repeatedly rendered it; the renders are all identical.

I should note the glasses from my first test are only a single Sketchup surface thick; that is, the outside of the glass is one Sketchup face, with the inside of the glass being the opposite face. (The base of the glass, which is the only other area to render differently in subsequent renders, is also similarly single-surfaced; with the top of the base aligned the same way as the outside of the glass.) Even though both faces of the glass were mapped with the same texture, something about the way Sketchup models the object causes problems with SunFlow.

I'm still uncertain why subsequent renders would generate different images or which variable(s) is being set to a different value in each render, but at least we know this isn't a general concern. However, it suggests some Sketchup models may not easily be made SH3D-safe....

maz
[Mar 13, 2016, 11:06:08 AM] Show Printable Version of Post    View Member Profile    Send Private Message [Link] Report threatening or abusive post: please login first  Go to top 
[ Jump to Last Post ]
Show Printable Version of Thread  Post new Thread

    Get Sweet Home 3D at SourceForge.net. Fast, secure and Free Open Source software downloads
   
© Copyright 2006-2024 eTeks - All rights reserved