Decal renderers display the particles as decals on the opaque geometry of the scene. A decal is a box that projects a texture on the geometry inside of it. In PopcornFX, the texture is projected from the top face of the box.
By default, the decal renderer is invisible and you need to enable the “diffuse” or the “emissive” feature to actually see it.
There are three different controls over the decal rendering:
- Fade Top: fade the decal depending on the distance to the bottom of the box: the closer it is the the bottom, the more faded is gets.
0 means no fade and 1 means “start to fade as soon as the geometry is closer to the bottom face than to the center of the box”
- Fade bottom: same as “Fade Top” but for the opposite face of the box.
- Fade Angle: not implemented yet. Should fade depending on the angle between the projected geometry and the box orientation.