Code:

---

action make_transparent
{
	my.transparent = on;
	my.alpha = 20; // play with this
	wait(1); // registers the above
	my.dynamic = off; // not dynamic to speed up rendering of this entity
}

---

This. Alpha is transparency. In Gamestudio, it uses a percentage, from 0 to 100. With 0%, it's the same as making it invisible. With 100%, it's fully opaque. With something in between, you can see through it. If you look out a standard window of about 5 millimeters, the glass has an alpha of 16 (6.3%) and thus easily able to be seen through. A thin trash bag would have an alpha of about 208 (81.3%) and very easily seen, but you can still see through it. For setting the transparency of each pixel individually, you'll need a 32-bit TGA or DDS texture image with alpha channel in it. GIMP is a useful program for making images with alpha channel.