How can I solve z-fighting using Three. Js

In ThreeJS, z-fighting is a common issue that occurs when two graphics are nearly overlapping on the same plane, causing flickering or zebra-stripe artifacts during rendering. This problem stems from the precision limitations of the depth buffer (Z-buffer), especially when two surfaces are very close, as the depth buffer cannot distinguish which one is in front.

Solving the z-fighting problem in ThreeJS can be approached with several strategies:

1. Adjusting the Camera's Near and Far Planes

By adjusting the camera's near and far clipping planes, you can optimize the use of the depth buffer. Ideally, set near to be as far as possible from the camera and far to be as close as possible to the farthest object, which increases the effective range and precision of the depth buffer. However, this approach has a drawback: if the objects in the scene are widely dispersed, it may be difficult to find an ideal near and far value.

javascript
camera = new THREE.PerspectiveCamera( 75, window.innerWidth / window.innerHeight, 1, 1000 );

2. Using polygonOffset

ThreeJS provides a material property called polygonOffset that can reduce z-fighting by slightly adjusting the depth values of each face. After enabling polygonOffset, you can set polygonOffsetFactor and polygonOffsetUnits to control the offset.

javascript
material = new THREE.MeshStandardMaterial({
    color: 0x808080,
    polygonOffset: true,
    polygonOffsetFactor: 1, // The factor affecting depth
    polygonOffsetUnits: 1  // The offset amount
});

3. Avoiding Overlapping Geometries

In model design, try to avoid creating overlapping geometry faces. If possible, modify the geometries appropriately to maintain some distance between them, which can fundamentally resolve the z-fighting issue.

4. Using Different Rendering Techniques

In some cases, consider using stencil buffer or shadow mapping techniques to handle or mitigate the z-fighting problem. These techniques process depth information in different ways, which may help resolve or bypass the z-fighting issue.

Example Project

In a previous project, I created a city building model with many walls and windows that were very close to each other. Initially, when the camera view was close to these buildings, noticeable z-fighting occurred. I resolved this issue by adjusting the camera's near and far values and applying polygonOffset to some overlapping window materials. This adjustment made the visual effect smoother, eliminating the previous flickering.

In summary, there are many ways to solve z-fighting, and the appropriate method should be chosen based on the specific situation. In ThreeJS, correctly using camera parameters and material properties can effectively mitigate or resolve this issue.