Skybox 360 Limitations

woochoo · Apr 27, 2009

Hi,
after looking round a few mas files it look to me like you can only have 6 different horizon/bkxx textures. At least it's the most i've seen. Those 6 maps cover around 90 degrees, so you can only have 90 degrees of accurate horizon mapping. I see they are re-distributed in order around the total 360 degrees to give some variation and the BTB/Krunch version (i don't know about others) has the option to mix it up with #5 and #6, but as i see it, one would need a total of 16 maps for a fully unique 360 degrees.

I've also read that if you muck with the gmt of the skybox/skyboxi/horizon that they wont work properly. Not sure why. My plan was to re-map the 16 individual panels of the horizon that Krunch has supplied in 3dsm. Does anyone know of any snags with this idea and is it related to the the sky icon that was visable in the teaser vid for v0.6 of BTB?

Eric Tozer · May 1, 2009

I'm sure it can be done & it makes sense to have 360 degrees of different horizons.
Just like in real life.
It's worth looking into.
I will put it on my to do list. (along with the rest of my life).

Martin Weare · May 1, 2009

If I change the BK0#.dds files in photoshop what format do i save them to get the invisible alfa grey above the horizon??

Is there a tutorial somewhere on how to edit horizons as well as sky boxes ?

Eric Tozer · May 1, 2009

You need to save them as DXT5 interpolated alpha.
Theres no tutorial as far as i know.

The important thing is to get them all to line up as some of them repeat.
I found the easiest way was to have all them horizons finish at the same height on the left & right edges

Martin Weare · May 1, 2009

Eric, are there any other settings? Ive created my image., 512/512 flattened image with grey horizon. DXT5 ARGB 8bpp | interpolated alpha. But I still have the grey strip in game where it is supposed to be invisible. When i go to 3d preview none of the images have a black background. only grey

woochoo · May 1, 2009

Martin, do you have an alpha channel in photoshop? alpha is a different concept to chroma key where you designate a colour to be invisable, but rather you designate pixel by pixel in a mask what is transparent on a %age of what is transparent (i apologise if you know this already).

For anyone who doesn't know, the alpha mask is defined in the channels section of photoshop (red, green, blue, & alpha (if you have an alpha channel)). It is a black/white image where black in transparent and white is visable, grey is semi visable). the way i do it for trees at least is to duplicate the blue channel, invert the colours (black to white, white to black etc), change the 'contras/brightness' til it fits the rgb image (i'm still using chroma for trees, not alpha), maybe do some work on the alpha mask with the eraser tool depending on the original rgb image, then save. this is probably only enough detail to get an average alpha mask, but it is a start. once you get the idea, try the selection>colour select tool. there would be MANY other people who could do this better than me and i hope they are on this forum and contribute a better guide to alpha masks.

i used 'explicit alpha' in the dds photoshop dialogue for horizon settings and i had the grey box. it has worked fine for my trees so far. for interest's sake i was just testing a 360 degree horizon with one image spread across the 16 horizon polygons. it was a big-wide image so i wouldn't try that for my final version.

so you say 'interpolated alpha' for the horizon, i'll try that next time

Do you have any details of specific differences between 'interpolated' and 'explicit'?

Martin Weare · May 2, 2009

Ho Woochoo. I'm totally new to all of this. I just blunder my way through. Finding tutorials is very hard.

I still need to learn how to

Creat an acurate horizon for my Coffs Harbour Track
Learn how to make my own 3D objects with textures.

I did put a post up offering a teamspeak channel for people to share information. Unfortunately only 2 or 3 people have joined in total so not much help there.

I have got BtB and 3D simEd and blender. Im starting to get my head around 3DsimEd but learning these proggies on your own is a daunting task.

Anyway, I'm allways on my teamspeak, you can get the details from my website: http://www.169thpanthers.com.au if someone feels like giving me a few basic lessons. I'll try to work out alpha channels today. Thanks again.

Eric Tozer · May 2, 2009

woochoo said:
Martin, do you have an alpha channel in photoshop? alpha is a different concept to chroma key where you designate a colour to be invisable, but rather you designate pixel by pixel in a mask what is transparent on a %age of what is transparent (i apologise if you know this already).

so you say 'interpolated alpha' for the horizon, i'll try that next time Do you have any details of specific differences between 'interpolated' and 'explicit'?

When using Chroma i don't bother with the "colour to be invisable".
I did try once or twice but it never really worked properly.
I assume it's meant to be like a "Green Screen" that they use in movies to drop in a new BG.
I just save with an Alpha mask & use curves on my mask to make sure there are no grey tones.
Even if you have a tone of 99% it will behave as 0% using Chroma, so you need to get your masks just right if using Chroma.

As far as using DXT3 explicit Alpha, i had trouble with this mode.
I was making guardrails with nice straight masks but once saved as DXT3 explicit for some reason the straight edges became bumpy.
So now do everything as DXT5. (unless it has no mask, then it's DXT1 no alpha)
I think it just gives a better result.

Eric Tozer · May 2, 2009

Martin_Weare said:
Eric, are there any other settings? Ive created my image., 512/512 flattened image with grey horizon. DXT5 ARGB 8bpp | interpolated alpha. But I still have the grey strip in game where it is supposed to be invisible. When i go to 3d preview none of the images have a black background. only grey

If you want you can email me your sky.mas file & i can have a look & see where it's going wrong.

ennisfargis (at) gmail.com

Cheers

woochoo · May 2, 2009

Eric Tozer said:
When using Chroma i don't bother with the "colour to be invisable".
I did try once or twice but it never really worked properly.
I assume it's meant to be like a "Green Screen" that they use in movies to drop in a new BG.
I just save with an Alpha mask & use curves on my mask to make sure there are no grey tones.

yep, i probably could have added that when i do 'chroma' i use the alpha layer rather than the basic/traditional 'key knockout' or whatever one might call it.

i have seen the errors when using explicit alpha but i wasn't sure why it was happening. I guess i'll move to DXT5 interpolated.

Martin, i can understand the daunting-ness of 3D programs. The good news is alpha channels are comparitivly easy

arty2:. good luck with it. as you can see i'm still learning too.

Martin Weare · May 2, 2009

I've spent the whole day trying to learn the basics of Blender. Lol! I still know next to nothing.

Martin Weare · May 3, 2009

Finally got the effect I was looking for.

woochoo · May 3, 2009

That looks really good. are you making a 360 degree horizon or just replacing the original BKxx images?

Martin Weare · May 3, 2009

it about 240 degrees. The east side is beaches so it wont be seen.

Eric Tozer · May 3, 2009

Nice :laugh2:

woochoo · May 29, 2009

evening gents, and any ladies who might be around,

i've been fiddling with a 360 degree sky box, and it seems there is no reason why it wont work.

in brief steps, this is what you have to do, in 3d studio max at least:

multi-subobject maps > gmotor material (as usual for gmt export)

assign a map (you'll need 16 maps with alpha channels) to each of the 16 pairs of triangles that make up the 360 degree horizon (in the case of Krunch's BTB skybox at least).

set each map as "source blend=src alpha" & "dest blend=inv src alpha"
set each map as 'no z-buffer'
shader 't1' i think, for each dx level.

export gmt "horizon" with only "move" ticked
edit: i've also set the shading to "none" and other as "use pointy normals"

so in brief steps, and as far as i can tell, that's what you do. there might be better settings (please chime in), but this got it working at least.

(if you edit the BTB skybox you should still give Krunch credit because of the altitude correction, assuming he doesn't mind it being edited...)

Emery · Jun 6, 2009

So, Martin, that looks marvelous!

I'm guessing that you applied the texture to the horizon with 3DSimEd after massaging the images in Blender? Or did you take another approach?

240 deg for a skyline would be excellent. The two tracks I'm putting together (Oregon International Raceway from 1964-1966 & Continental Divide Raceway circa 1965-1970) back into a mountain/hill and, like yours, you can only see 240 deg of horizon from the track anyways.