solved Cubemap SKYBOX_MODE projection origin

[V!nc3r]

Hi all!

I need to reproduce an effect 360-wall-mapping like. To do that, a cubemap projection using SKYBOX_MODE is perfect.

Here my example playground: http://www.babylonjs-playground.com/#JCZIXE#7:

• click on Cubemap02 button (this assign a cubemap using SKYBOX_MODE)
• you can see that the skybox projection use the object origin as projection origin (screenshot from Blender, showing where is the object origin)
• click on switch cam button: this teleport you on a FreeCam at the object origin (the orange sphere), and you can see that the cubemap isn't deformed at all despite of its projection on the 3D mesh: that's the result wanted.

BUT: click on the Cubemap01 button: this applied another cubemap on the mesh, using the same object origin... Except I want to project this lightmap from the green sphere point of view.

Only for reference, if you unzoom you will see the same object duplicate twice but with different origins, showing cubemap projected from other coordinates.

(you can download test scene sources here).

So my question is: is it possible to dynamically change the center of a skyxbox cubemap projection?

Potential bonus: couldn't this projection technique leads us to point light cubemap shadowing?

[Sebavan]

We do not support changing the center as by default cubemap are considered at infinite distance so would look the same.

You could try to use local cubemap for this section Using local cubemap mode of http://doc.babylonjs.com/how_to/reflect#cubetexture

[V!nc3r]

Yes but it seems local cubemap mode doesn't work with SKYBOX_MODE http://www.babylonjs-playground.com/#JCZIXE#8 (line 74), and unfortunatly the SKYBOX_MODE is the only way to get the texture projection I want.

[Sebavan]

Yup this would be interesting to add indeed, I ll check what I can do.

[sharp]

1 hour ago, Sebavan said:

We do not support changing the center as by default cubemap are considered at infinite distance so would look the same.

Can't we fake the center ? We tried to change pivot point &  matrix / reflectionTextureMatrix, = without success ?

[Sebavan]

Ok I got something allowing adding a reflection texture matrix for skybox mode.

Basically the matrix will fit with your translations from origin to new origin.

I will make a PR and new release ASAP.

[Sebavan]

The pull request is out : https://github.com/BabylonJS/Babylon.js/pull/4982

The result once deployed will be testable on: http://www.babylonjs-playground.com/#JCZIXE#9

Basically you can add this on the texture to offset it:

// Offset the skybox center.

var point1ToPoint2 = cameraPoint02.position.subtract(cameraPoint01.position);

var reflectionMatrix = BABYLON.Matrix.Translation(point1ToPoint2.x, point1ToPoint2.y, point1ToPoint2.z);

otherOriginRefMat.reflectionTexture.setReflectionTextureMatrix(reflectionMatrix);

 

[V!nc3r]

You roxx! 'can't wait to test that ?

[V!nc3r]

It works \o/

Thanks :)

[Guest]

Excellent! Flagging as solved!

[V!nc3r]

And is this new functionnality can help to get point light cubemap shadows?

[V!nc3r]

Yay! Updating skybox position on each render : http://www.babylonjs-playground.com/#JCZIXE#12

Nice job @Sebavan

[Guest]

Excellent!