When viewing models in AR in Sketchup for iPad and in SketchUp Viewer on iPhone, I get flickering shadows as the device moves. It’s the same issue on three devices (iPhone 15 Pro, iPhone 15 Pro Max, and iPad Air 4th gen) and with models of every complexity that I’ve tried, ranging from 3 MB (32 polygons) to 30 MB (1 million polygons). The use case is demonstrating models live for online and in-person audiences, and while it’s not dramatic to my eye, a couple of audience members have said that the flickering makes it too uncomfortable and confusing to look at.
I don’t see a way to turn off shadows or change their settings in AR, as shadows in AR don’t seem to be linked to shadow settings in the model. Outside of AR, the shadows in the model and in movie exports are all fine. I don’t see other options that help - changing to classic graphics engine on iPad doesn’t seem to affect AR. The flickering in AR seems to be related to device movement - high-frequency flickering when moving the phone/iPad, but just occasional erratic flickers when the phone is on a tripod.
When viewed in AR the model is converted to USDZ. That can end up making reversed faces be invisible, or other issues that you won’t see in SketchUp. Most things should be fixable with changes in the model.
Can you reply with a small example file, and say what sort of flickering it causes? You could even do a screen recording on iPhone or iPad, to show the issue.
Thanks for the reply, Colin. Here’s a screen recording example (sorry - vertical video). It happens with all models, including the example Dance Centre.skp file. It’s not bad to my eye, but enough that some of the clients in my audience say that they don’t want to watch it.
Thanks, Colin. Yes - it’s the same material front and back of the face when I remove the other geometry. Sorry - I’m reluctant to upload the actual models I’m using as I don’t have IP over them. Here’s a similar-looking issue on the unmodified Dance Centre model, so we can see it on the same model. I’m not sure if it as the same, as it doesn’t seem as bad - maybe because there’s less fine detail to show the dancing?
Hi Colin, We move the phone by hand through the virtual model, rigging it in a cinema cage or on a gimbal if we need more stability. The flickers seem to happen when the phone thinks it’s moving - faster flickering when the phone is moving quickly and slower flickering when it’s moving slowly. When the phone is stationary on a tripod, the flickers still happen but infrequently and erratically, likely when the phone just thinks it’s moved.
The location of the video is opposite the front entrance of the Dance Centre. Here’s the route there:
Frankly, it’s embarrassing to me as a film-maker that I didn’t include an establishing shot!
Anything that flickers when you’re not moving will also flicker when you orbit while editing the model. That’s normal z-fighting, and is caused by faces being in the same place as each other. there are a lot of those around the edge of the roof. If you carefully delete the extra faces, and redraw holes that appear, you can fix that in the model, and then it will be fixed in the AR scene.
The faces that flicker only when you move seem to be caused by the default material being messed up. One of the early materials is named Layer_Layer0. If you paint the walls that flicker with that, instead of the default material, the flickering when you move seems to stop.
Thanks, Colin - you’ve helped to narrow it down. No faces are flickering, it’s movement of the shadows relative to the model. It only happens in AR view in Sketchup for iPad and in AR view in Sketchup Viewer. I’ve made a “shadow torture-test” model to show the issue, and attached the model and a video showing the issue more clearly.
The shadows don’t move when editing the model and the shadows don’t move in iOS native AR Quick Look when I export the model as USDZ from Sketchup for iPad, regardless of whether I set the USDZ metadata to use IBL version 1 or 2 in Apple’s Reality Converter. All the shadows stay rock-steady on the model in AR Quick Look. The shadows only move in Sketchup’s implementation of AR.
The movement seems to affect shadows on all surfaces regardless of material. It’s most visible on small details - the closer you get, the more the shadow appears to move.
In a nutshell, the edges of the shadows aren’t moving in sync with the model when the device updates its position in space when showing AR view in Sketchup.
Sometimes it looks like faces are flickering, but that’s just an edge-case of the issue: faces seem to flicker only when the face lies roughly parallel to the direction of light, so the whole face lies equally in its own penumbra. As the penumbra dances around, the whole face gets brighter or darker at once. But rotate the model and the flickering then disappears from that face and appears on any other faces now parallel to the light.
Can you offer any help to stop it happening? The only solution I can think of is to put a huge “roof” high up over the models to kill the directional component of the lighting that causes the problem, but that will mess-up the automatic sizing of the AR model, and make it a pain for people to use (they’ll have to literally duck under a virtual roof!). And I like the lighting model that Sketchup uses in AR - it’s a shame to have to shade everything just to stop the flickering.