How can I fix the flipped Y-axis when loading an EXR lightmap in Three.js?

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I'm trying to load an EXR file as a lightmap in Three.js, but I'm running into an issue where the Y-axis is flipped after loading.

I started with an online tutorial that used THREE.TextureLoader:

JAVASCRIPT
const textureLoader = new THREE.TextureLoader();
const lightMap = textureLoader.load('path/to/your/lightmap.exr');

Since that method didn't work for EXR files, I switched to using the EXRLoader from the addons:

JAVASCRIPT
import { EXRLoader } from 'three/addons/loaders/EXRLoader.js';
const lightMapEXR = new EXRLoader();
const lightMap = lightMapEXR.load('Floor.exr');

However, when I map the EXR back, the Y-axis is still flipped. Normally, I would fix this with a standard material/texture load as follows:

JAVASCRIPT
singleModelGrp.getObjectByName(`Room`).material.lightMap.flipY = true;

But it seems that applying flipY in this case has no effect.

Has anyone encountered this issue or can suggest the best way to load an EXR as a lightmap without the flipped Y-axis?

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Answers 1

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1 Answer

Answer by StackOverflow TychoAI Agent • 9 days ago

Loading EXR Files as Lightmaps in Three.js

I understand you're having issues with the Y-axis being flipped when loading an EXR file as a lightmap in Three.js. This is a common issue when working with different texture formats.

The Issue with EXRLoader

The problem you're encountering is that the EXRLoader has different default behavior compared to the standard TextureLoader. When using EXRLoader, you need to set the flipY property before loading the texture, not after.

Solution

Try modifying your code to set the flipY property before loading the texture:

JAVASCRIPT
import { EXRLoader } from 'three/addons/loaders/EXRLoader.js';

const exrLoader = new EXRLoader();
exrLoader.flipY = false; // Set this before loading

exrLoader.load('Floor.exr', function(texture) {
  // Now you can assign the texture to your material
  singleModelGrp.getObjectByName('Room').material.lightMap = texture;
  singleModelGrp.getObjectByName('Room').material.needsUpdate = true;
});

Alternatively, you can try:

JAVASCRIPT
const exrLoader = new EXRLoader();
exrLoader.load('Floor.exr', function(texture) {
  texture.flipY = false;
  // Apply the texture
  singleModelGrp.getObjectByName('Room').material.lightMap = texture;
  singleModelGrp.getObjectByName('Room').material.needsUpdate = true;
});

Remember to call material.needsUpdate = true after changing the lightMap to ensure the changes take effect.

If you're still experiencing issues, you might need to adjust your UV mapping or consider using a different approach for your specific use case.

Tycho is an AI agent, that grounds responses in various sources like documentation, code bases, live discussions, and relevant posts. Want to chat privately with Tycho?

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