View Full Version : Potentialy a large render/geometry problem 2018

02-10-2018, 05:52 AM
Hi, this is furthering a problem i have found in the render engine (although i cant pinpoint the exact cause) unfortunately the bug system seems to have stopped working for me and wont let me upload attachments (i have emailed tech directly with links so hopefully they can take a look)
this is what i bugged

"Hi, its a little hard to pin down the exact cause as it seems to be a two part problem, if you load scene v1 in attached folder, render frame 3 on my system it takes around 2 mins to complete, if you then render frame 2 the renderer becomes stuck around the area of the rear vent far right hand side, the only difference between the two is that the tracks of the tank are behind the problem area, the render time then increases to anywhere up to 2 hours!
at first i thought it may be due to bad geometry on the vent fins so i made a copy of the scene (v2 in attached folder) with the vents removed so the problem area is just a flat smooth surface, but the render times still persist.
i have actually found this issue in a large number of similar models as i build a lot of models for 3d printing and this scene is used to present the models to the customer (i have about 3000 to date and out of the 10 i tried so far about 50% have the same issue where 3 renders will take 30 seconds to a min, then a forth render will take anywhere from 15 mins to 3 hours! obviously this is a big problem when i just need quick renders for customers)"

so essentially, this render takes just over 4 mins at 4k with the tracks moved out of position
move them back into place, and the renderer gets stuck in the area highlighted for around 2 hours!!!
so not even linked to the part that has moved into position as it already rendered that area with no problems, so i thought maybe its bad geometry, so i removed the vent, but no, it still gets stuck in the same area.
and this is not an isolated problem, i have around 3000 models like this (basically 3d print kits with multiple layers, each layer is a part of the kit) out of the handful i have rendered in 2018.0.1 nearly 50% of them have at least 1 render that has this problem, so the problem seems to be linked to the angle of view to what ever the problem is (seems to be one object behind another is the only thing that is common in the scenes),
the models are fairly clean, no 1,2 point polys, all tripled, unified normal etc, the scene is simple, no gi just a single enviro light, simple single surface with no spec or anything, small amount of aa and most of the render bounces set to 1

02-10-2018, 06:03 AM
also i should point out as you can see in the second images its getting stuck in the first pass before it even starts doing the blue AA passes

02-10-2018, 06:45 AM
And to add a little further, it seems the render times seem to exponentially increase relative to the position of the tracks, if i move them a few mm sideways the render time drops from 2 hours to 13 mins, fully away 3 mins!

02-10-2018, 07:28 AM
I wonder if the problem you are seeing/having is similar to the one people found with the Sea Quest scene in a previous thread ? :


02-10-2018, 07:55 AM
yes it is and i worked out the fix, you have to select the correct render tile size, for the seaquest scene setting it to 64 and the problem goes, renders in about 4 mins, for my tank scene i had to set it to 128, if you set higher again then the problem starts to return, so it looks like for every scene you have to render a test image with each tile size first, the problem is if you move the camera it seems to change the size of render tile you need, this is not good as it looks like animations are out of the question!

02-10-2018, 10:58 AM
I can also confirm the bug is not present in 2018.0.0 but is in 2018.0.1

in fact, it also shows that 2018.0.0 renders my tank scene considerably faster than 2018.0.1, 30 seconds compared to 4.5 mins! seems the fixes in the last build may have broke more than it fixed!

02-11-2018, 04:35 AM
Good find... Did you report all of this with the content? Hopefully they'll get right onto this and fix it!

02-11-2018, 09:31 AM
yes, they have fixed it, it will be in the next patch, its supposed to be along very soon, they also confirmed with the content i sent them.

02-11-2018, 09:54 AM
Awesome!! They're not wasting any time at the moment... Great to hear!

02-11-2018, 11:44 AM
Good news.. as it confirms that they [LWG team] are very active in responding to issues. Very good indeed!