TextureProjector .setFallOffPower doesn't work with parallel projection

I’d like to project a Texture with a falloff (fading) effect.

If I operate the projector’s camera and do Camera.setParallelProjection(true), the falloff effect does not work anymore. Is it a bug?
I’ve tried to adjust the frustum, but without the ParallelProjection I find it difficult to cover the area I want.

mhhh… what is TextureProjector?

Is a plugin:

However, my problem is that I don’t fully understand the camera.setFrustum(float, float, float, float, float.float) API.
I’d like to project a Texture without distortion, so ParallelProjection is probably desiderable, but this breaks the falloff effect for me… :frowning: