God rays / particles and opacity map not working on primitive

arnon

So I copied / build a god ray and particle effect (primitive box with no reflection, some refraction and SSS) and it looks really good. However I want the box to fade out left to right as a point light (ambient light to light up the scene a bit) on the right interferes with the hard moonlight (spot light) through a window on the left.

So I put a white to black transition map into the opacity slot and left it at 1.00. The whole effect is gone! I thought perhaps I mistook the opacity colours or values, so for testing I put a white map and black map into this slot, changed the value - nothing. As long as there's whatever texture loaded the effect is zero. When I switch to none, the effect is there and the opacity slider works.

I want the effect to fade out left to right, what am I doing wrong?

magog_a4eb71ab

I could be wrong as I'm not entirely sure how the effect works in relation to the geometry of the primitive & the camera's orientation, but you should be aware that when using a cube primitive, the sides will not be textured properly for what you're trying to do unless you make an appropriate UV map for the object(i.e. the cube primitve). I was going to say try situating 6 plane primitives together to form a cube and use the proper gradient texture(s) on each face so that you have the effect of the cut-out opacity fading from one side of the cube structure to the other, but it probably needs to be one solid piece of geometry(having volume) for the effect to work, assuming that it does work. It might not work and you would end up having to rely on post-work editing in something like photoshop or similar free-alternative.

You should experiment with other non-primitive objects with a UV-map that you could do this with.

arnon

yes, I forgot about the proper UV map setting and naively considered this a left to right effect on just one plane. I have to unwrap it. Thanks!