OK,
I'm confused.
But then, I'm learning Terragen; of course I'm confused..............and frustrated.
Right - I'm trying to create a simple {err...cough..} planetary ring using image maps and a disc object.
I was working on a tutorial but when the instructor started to use multiple discs to create multiple rings, I thought... I'd better not say what I thought.
Now, I have numerous tgd/tgc files for procedural rings (some with rocks, some without) but I wanted to use image maps because, at this stage of my learning, I understand image maps (although I am still confused with mapping modes but I have that sorted in this case.............. even if I'm not quite sure why....).
Now, I started with using an Image map shader connected to the Default shader the disc already had (why the Image map shader can only connect to the colour FUNCTION input rather than the colour IMAGE input of the Default shader is beyond me, but there you go.........) but discovered the Default shader already has the ability to map images onto a surface so went with using the Default shader only.
I managed to get an image mapped to the disc (colour) but really started to have issues when I tried to create any sort of opacity variation (to create the multiple ring/variable density ring structures).
1. When opacity is set below 0.5, the disc is invisible! Why? Even if I set the opacity to 0.49, there's no disc (screencap 1) - however, it's shadow is still there........... This is whether an image map is mapped to the disc or not.
After a lot of stuffing around (a technical, scientific term - I have a B of App Sci - I know what I'm talking about... yeah sure...), I decided to try being a bit more methodical; even if my results didn't reflect the same...............
2. When I tried using a simple big, black 'E' on a white background as a transparency map and started to get some results I understood (screencap 2).
3. Then, keeping the same map, I changed the opacity setting to 0.5 (screencap 3a) - the big E is still clearly working but notice the "spottiness" of the remaining disc..........
Then again, the same setting except for the opacity being dropped from 0.5 to 0.49 - only a miniscule change with a not so miniscule change (screencap 3b).
4. Up until now, the transparency map was a simple jpg; I thought I'd try a tif with a transparent background (so, only the big black E) (screencap 4a). Here, the transparency appears to have made the whole thing transparent..........
Then the same but with "Use alpha map" checked (screencap 4b). Now black appears now appears to be opaque, but that's because the alpha would be white; yes? So it's white that "keeps" the image opaque/visible?
5. OK; let's test this theory with a big white E with a clear background......... (screencap 5). So white "stops" the transparency function........I think.
All of this has me rather confused and I have yet to do the same with the ring colour map (Changing it to greyscale, inverting and then using it as a transparency map). This is because I need to understand the concepts I have highlighted in this post...
So the problems remain; why can't I get degrees of opacity/transparency? As it stands, white is opaque, black is transparent and greys having more black than white are transparent whilst greys with more white than black are opaque!
There appear to be no shades of grey........ literally.
Help!!
FYI; The last 2 images show the type of effect that I am after (regarding the rings); but these are out of Vue (which has considerably more issues than Terragen)...........