View Full Version : Rendering Artifacts (not 1, 2 pt polys)

04-10-2015, 01:57 PM
Didn't want to hijack the other rendering artifact thread, cuz this is totally different.

See video clip link below (uploading as an attachment didn't work). See the dark horizontal streaks in the first scene and the choppy horizontal blocks on the ground plus darkened streaks in the second scene (same animation)? The areas shown are enlarged 4 to 5 times from the 720 HD rez sequence.


ANY idea what's causing them? Anybody confirm?

It looks to me like it's caused by the instanced gravel nuggets. The scene is using animated cache, interp MC (2 bounce, 500 RPE, 50 SBR, 4 pix min, 100 pix max spacing, baked at frame step 1 - resulting in a single cache file - thus using the pre 11.6 anim cache method where existing samples from the previous frame are reused and new samples added to the cache file only as new geometry becomes visible). The instanced objects (gravel nuggets) were set to Unseen by Radiosity, but not the emitters, driven by DP_MDD Emitter custom obj plugin using a PFX calc scanned to MDD in order to get single-pass particle motion blur).

I'm rebaking the scene's GI over again (now) with the nugget's Unseen by Radiosity unchecked and rendering the 1000 frame scene again over the weekend to see if this is the cause of the streaks and wonky ground texture artifacts. If so, looks like another Unseen By Radiosity bug.

04-10-2015, 02:11 PM
Are you rendering out an image sequence or a quicktime file? Because to me, it looks like a compression artifact coming from a Quicktime codec. The black lines stay horizontal even when the camera is rotating. I have seen this happen when I've brought in an image sequence into After Effects, then rendered out a Quicktime with some type of codec. Sometimes the settings in the codec can clean this up.

If your frames are actually rendering out of Lightwave like this, then I'm stumped. I've never seen that before.

04-10-2015, 02:33 PM
It's a LW (jpeg) image seq., and all other anims of this same scene (including interior shots with nearly a million instances of the same nuggets "unseen by rad") render without such artifacts.

04-10-2015, 02:58 PM
I'd recommend trying a different format. LightWave doesn't handle JPEGs well and it is better to render to a lossless format anyway and then compress in post. Using JPEG, you're throwing away data right at the start and it requires more processing just to write the file than, say, PNG or TIFF. Will it use more disk space? Sure, but that's the point. Give the post processor a full dataset and let it throw away what it doesn't need to write the animation at the level you require. Even if this doesn't cure the artifacts, it's a better workflow.

04-13-2015, 06:10 AM
Rerendering with the instanced objects seen by radiosity did not fix the streaking and chopping up of the ground (obviously, there's no texture animation whatsoever applied in any form). I'll switch to PNG and see how that goes. The only other test I could do it disable instance rendering and/or DP MDD_Emitter and see what happens.

04-13-2015, 07:19 AM
Nope. Not a JPG issue. Got the same artifacts with PNG.

04-13-2015, 07:53 AM
It looks to me like you have coplanar geometry - that's to say that there are two groundplanes in pretty much the same place (or at least Y height).


04-13-2015, 11:49 AM
Nope. Single ground plane mesh. No co-planar polys. No duplicates. etc. If that were the case, then how would that relate to the slightly darker horizontal streaks?

I turned Instances off and rendered a couple seconds worth of frames and the ground was rock solid and no dark (by a smidge) horizontal streaks across the frames.

I'll now turn the front mixer paddle instances on and see what happens. There are four emitters, all PFX created and then scanned to MDD. PFX then disabled/deleted from emitter objects and replaced with DP's MDD_Emitter custom obj plugin, then instancing applied. 1st emitter is the mix exiting the dryer drum, 2nd is the asphalt being sprayed on to the rocks, 3rd is the front rotating mixing paddles, and 4th is the back set. So, in total, around 5K particles being rendered on any given frame.

04-14-2015, 07:44 AM
I think I've narrowed down the cause of the render errors/artifacts to the presence of multiple instances of DP MDD_Emitter in the scene. I disabled all but one and the ground rendered without breaking up. Then I enabled MDD_Emitter on a second emitter null object, thus two instances of the plugin running, one each on two different nulls, and the ground texture chopped up. Then I disabled the first and switched it to PFX, leaving the second MDD_Emitter enabled, and all was well again.

Since there are four MDD_Emitter instances in this scene, I'll have to revert to creative ways around the problem, such as making a Scene A and Scene B to divide the visibility and enabled/disabled state of the emitters.