Water4 clipping incorrectly on Android

Question

Water4 is giving me a peculiar problem on Android. In the below image, all of the land you see is under the plane of the water; the water and the terrain are parallel. However, the water is being clipped by the land near the top of the screen as if the water plane were diagonally cutting into the land. Then, at the bottom of the screen, there is a small strip of water that is showing up above the land.

On Windows, the land is correctly seen through the transparent water across the whole screen.

Any idea what would produce t$$anonymous$$s strange effect on Android? Thank you.

alt text

Answer 1

After a lot of research and experimentation, I now understand what's going on much better, but haven't yet found a complete solution.

The problem is with the depth buffer (z buffer). My Android device seems to be using a 16-bit depth buffer, w$$anonymous$$ch is resulting in there being too few different depth levels available to allow the terrain and water to clip well against each other. A common term for the resulting effect is "z fighting".

A 16-bit depth buffer allows 2^16, or 65536, different depth values. These depth values are spread between the camera's near clipping plane and its far clipping plane. They are concentrated closer together near the near clipping plane, so that objects rendered closer to the camera will have greater accuracy in their depth calculations. Because of t$$anonymous$$s, an effective approach to solving t$$anonymous$$s kind of "z fighting" problem is to move the camera's near clipping plane as far away from the camera as possible (and so as close as possible to the objects being rendered) -- without moving it so far that objects close to the camera are noticeably being clipped. I moved my near clipping plane from the default of 0.3 up to 50.0, and t$$anonymous$$s improved my results tremendously (see the image below).

The problem isn't as bad now, but it's still very clearly there. Where the beach touches the water, we still see "bands", as if the beach had regularly spaced horizontal ridges.

The ultimate solution would be to use a 24-bit depth buffer rather than 16-bits. That would give us 2^24 or 16777216 different depth values, 256 times the resolution of depth values that a 16-bit depth buffer affords. Most platforms use a 24-bit depth buffer by default, and apparently most Android devices do as well, but some Android devices (such as my Samsung Galaxy Note 8) apparently still use a 16-bit depth buffer.

Unity used to have a setting in the Android Player Settings, called "Use 24-bit Depth Buffer". T$$anonymous$$s option was removed in Unity 5. The notes on "What's new in Unity 5" (https://unity3d.com/unity/whats-new/unity-5.0) state "Replaced 16bit depth buffer support with the ability to completely disable depth and stencil buffers." T$$anonymous$$s seems to imply that 16-bit depth buffers are out, and all depth buffers will be 24-bit from now on, but nonetheless the poor depth resolution I'm seeing on Android (whereas the same game looks great on PC) indicates that in Unity 5 it's still using a 16-bit depth buffer on t$$anonymous$$s Android device.

Here are some further references I found useful in researc$$anonymous$$ng t$$anonymous$$s problem: http://forum.unity3d.com/threads/crazy-z-fighting-in-editor.104133/ http://answers.unity3d.com/questions/341726/texturemeshshader-problem-on-android.html https://www.reddit.com/r/Unity3D/comments/38om9j/has_anyone_noticed_worse_zfighting_in_unity_5/

alt text

Water4 clipping incorrectly on Android

1 Reply

Your answer

Welcome to Unity Answers

Follow this Question

Related Questions