Handling Shader Precision in Three.js

Based on your experience with shader precision issues on Android devices, I can provide some guidance on how to handle this in Three.js.

Three.js Precision Handling

In Three.js, you can specify the shader precision when creating a WebGLRenderer instance. Looking at the constructor documentation, there's a specific parameter for this:

JAVASCRIPTCopied
const renderer = new THREE.WebGLRenderer({
  precision: "highp" // Can be "highp", "mediump" or "lowp"
});

By default, Three.js uses "highp" if supported by the device. This is generally the safest approach for consistent rendering across different platforms.

Best Practices for Shader Precision

1. Use the renderer's precision setting: Let Three.js handle the precision declarations in your shaders by setting it at the renderer level.

2. Consider conditional precision: If performance is a concern on some devices, you could detect the device type and set the appropriate precision:

JAVASCRIPTCopied
const isMobile = /Android|webOS|iPhone|iPad|iPod|BlackBerry|IEMobile|Opera Mini/i.test(navigator.userAgent);
const precision = isMobile && !isIOS ? "highp" : "mediump";

const renderer = new THREE.WebGLRenderer({
  precision: precision
});

3. For custom shaders: If you're writing custom shaders in Three.js, you generally don't need to include the precision declarations as Three.js will handle this for you based on the renderer settings.

Recommendations

Based on your specific issue:

1. For most cases, using "highp" is the safest option for consistent visual results across devices.

2. If you're concerned about performance, you could implement device detection and use "highp" specifically for Android devices while using "mediump" for others.

3. When writing custom shaders in Three.js, you can typically omit the precision declarations and GL_ES conditionals, as Three.js will inject the appropriate precision based on the renderer settings.

4. For your specific case, since the visual difference is significant, prioritizing "highp" for Android seems like the right approach.

Remember that using "highp" might have some performance impact on lower-end devices, but modern hardware should handle it well in most cases.