Flickering shadows/textures on sharp angles from light source

[ItsMashBro]

I'm getting this flickering effect on certain placed items in my world. It only happens when viewing the item from certain angles, but if I look at it straight on it goes away. I'm not sure if there's more, but it's happening with my pots and item frames, as well as on the items within those frames.

I'm using the "Fast Item Frames" mod, so to rule out any incompatibilities I temporarily removed the mod to make sure that wasn't the culprit.

I'm unable to provide a video of the issue until later, but here is a photo I was able to capture while the flickering was happening. It's hard to tell, but the color of the item is much darker than it should normally be

The effect is very similar to what you might see when you have texture z-fighting in other games, maybe that helps you visualize what I'm seeing

[ItsMashBro]

Some further info:

I'm using the shader on the Low setting

PC:
Ryzen 7 5700x3D
3060 12GB
32GB RAM

[javiergcim]

What happens if you use the default textures or resource pack?

[ItsMashBro]

It still happens even with the default textures, and any resource pack I've tried. Recently I've been using vanilla textures so I can use connected texture packs, but that came after.

I did note that when I turn the shadows down to "Low" it becomes slightly less noticeable. The items are not that annoying, but my horse's armor is flickering like a christmas tree

[javiergcim]

Please send the minimum necessary information so we can try to reproduce the issue and attempt to fix it:

• Minecraft version
• Are you using OptiFine or Iris?
• Forge / Fabric version used (if the shader mod was installed manually in one of those loaders)
• Have you verified that the issue is not caused by an update to OptiFine/Iris or Minecraft rather than a shader update?
• If it is the shader, which is the latest shader version that does not have this issue?
• Have you verified that the issue does not occur with other shaders? If so, which ones?

Thank you.

[javiergcim]

Please reset the shader settings and see if that resolves the issue.
Check whether “pixelated” shadows are enabled.

You also haven’t told me which shader version you are using.
Are there specific objects that show this problem?
From which angle does the error appear?
Does the sun need to be in a certain position?

[javiergcim]

Without a clear image of what you’re experiencing, it becomes even more difficult to figure out what the problem is. An animation or a sequence of images showing that “flickering” would be very helpful.

[ItsMashBro]

I'll report back with a short clip and all the info requested

[javiergcim]

WAIT A MOMENT! QUESTION: Did you download the shader from here (github.com)? Based on the symptoms, I suspect you might be using a development version from when I was implementing pixelated shadows.

Either way, download the latest version of the shader from here to rule that out:
https://modrinth.com/shader/makeup-ultra-fast-shaders

[ItsMashBro]

Github is giving me trouble with the video file so here's a link to it on Imgur:

https://imgur.com/a/Du8R1DC

Version number is 9.4a, which I downloaded from the Prism Launcher the same day that I opened this ticket. The error happens on items inside item frames. It also used to happen on my horse's leather armor, but NOT on his iron armor. It occurs from all angles and all times of day/night, even if the item frame is placed flat on a table or something. I have a golden apple laying flat on a trapdoor and it has the same effect. It also happens when the item frames are not hidden.

Pixelated shadows is turned on and set to 32x32 and the error still occurs when set to 16x16 as well

1.21.11 Mod List (Mash).html

I attached an export of my mod list, although mostly performance mods, in case that helps. Could Nvidium interfere with things? It's not compatible with shaders, but it's supposed to disable itself when shaders are enabled so I figured it's safe to keep it there. I've never noticed any obvious signs of trouble with it unless it's affecting my fps somehow

Also if you could point me to which settings will let me tweak the general brightness and contrast by a tiny bit that would be awesome. Some of the advanced lighting settings I had a hard time understanding exactly what they do.

Really appreciate all this help!

[ItsMashBro]

I just noticed Imgur destroyed the resolution of that video. If you need a better one I'll try a different way.

https://drive.google.com/file/d/1RVJuhqYzBjyvAz2FPOHRpubvSpMIL7Yl/view?usp=drive_link

Literally only marginally better xD

[tasxatzial]

I can confirm this is also happening on 1.20.1 with the default Makeup config of 9.4a

List of mods:
fabric-api-0.92.7+1.20.1.jar
indium-1.0.36+mc1.20.1.jar
iris-1.7.6+mc1.20.1.jar
reeses_sodium_options-1.7.2+mc1.20.1-build.101.jar
sodium-extra-0.5.9+mc1.20.1.jar
sodium-fabric-0.5.13+mc1.20.1.jar

[tasxatzial]

One more thing. It only happens with glowing item frames, not regular frames. Haven't tested with other things.

[EntokitoDezonze]

I found where problem happens.
solid_blocks_vertex.glsl

find:

    #if defined GBUFFER_ENTITIES
        if (entityId == 10102) {
            isEmissiveEntity = 1.0;
            directLightStrength = 1.0;
        }
    #endif

    Remove everything here.

Removing isEmissiveEntity = 1.0 fixes the bug. But I do not think that is what you want to do.

solid_blocks_fragment.glsl

find:

    #if defined GBUFFER_TERRAIN || defined GBUFFER_HAND || defined GBUFFER_ENTITIES
        if(isEmissiveEntity > 0.5) {
            finalCandleColor *= block_luma * 1.5;
        }
    #endif

Replace by

    #if defined GBUFFER_TERRAIN || defined GBUFFER_HAND || defined GBUFFER_ENTITIES
        if(isEmissiveEntity > 0.5) {
            finalCandleColor *= block_luma * 1.5;
        }
        #if defined GBUFFER_ENTITIES
            if (entityId == 10102) {
                finalCandleColor *= block_luma * 1.5;
            }
        #endif
    #endif

I recommend that you perform an entity check in FRAGMENT. Doing this will fix the problem.

Hope that I helped.

[javiergcim]

I see that it happens to several people; unfortunately, I can’t reproduce the problem on my system. Everything looks perfectly fine here—no flickering—using the same versions of Minecraft and Iris shown in your video. Without being able to reproduce the issue, it’s practically impossible to fix the bug (and it’s clear that it’s not in the shader; it must be something else. What exactly? No idea. It could range from the video driver, the Java virtual machine version, or any number of other things).

PLEASE CHECK WHETHER IT HAPPENS WITH THE NORMAL SHADOWS (NOT THE PIXELATED ONES).

(Does it only happen in MakeUp, or does it happen in other shaders as well? Does it happen in Vanilla?)

It would be good to know which OS and GPU you are using. I’m testing this with an AMD Radeon RX 9070 XT, an NVIDIA RTX 3050 Laptop, and the integrated GPU of an Intel CPU, all on Linux. The problem does not appear on any of them.

I’ll still take a look when I can to see whether the positions of the two objects (the object and the enchantment) are being calculated differently or through different paths.

@EntokitoDezonze I highly doubt that the code you posted here has any relation to the problem, which is almost certainly z-fighting.

The code you shared changes the brightness that a glowing object produces on itself. Perhaps the brightness change you introduce dampens the effect, but it wouldn’t be related to actually solving the issue.

BUT if you can post a video of your solution in action so we can see what’s really happening, that would help.

Since it doesn’t happen on my system, I can’t verify it myself.

The objects are detected in the vertex shader and not in the fragment shader, because doing it in the vertex shader is faster (it’s done once per vertex rather than once per pixel of the image).

[EntokitoDezonze]

@javiergcim I also found the cause of the problem strange, as I know that the code on vertex detects entity_flame. It seems to me to be an entity detection bug, I also know that it can be slower, but the impact of this correction was zero in my tests. Here is a video showing the fix in action:

https://streamable.com/dasypb