January 27, 2016, 10:24:08 pm
Hi ak2rz, here's how:
Add a Standard material to the object in Lumion, add a texture with an alpha channel (see the video below) to the Color Map slot in the Standard material, then click on the More button, select the Advanced module and finally click on the Scissors button at the bottom.
Please note that the Standard material only supports a 1-bit Clip mask, so each pixel is either fully transparent (black) or fully opaque (white). If your Clip mask contains greyscale tones, they will be rounded up/down to pure black/white.
Here's how to make a transparency mask in the Alpha channel of the texture in Photoshop, i.e. saving it as a 32-bit TGA or BMP texture (see the video below).