Friday, 15th September, 2006

Bleeding Textures

OK, apologies first. This could well be a complete no-brainer. Honestly, I'm almost expecting a "Well, DUH" comment from K , and the inevitable "Yup, that's what EVERYONE does doofus". But still, it's something I've worked out all by myself, and in my time-honoured-tradition of jumping up and down going "Whoo! Look what I did!", I wanted to share. Also, this is a post about texture baking in Second Life, and has nothing to do with my 'usual' subject matter. If you're expecting to see a picture of me in a dress halfway down the page, then I'd look away now. Personally.

OK, a little bit of history second. I have (as Ali' noted on yesterday's post) been building a gallery in Second Life to show my (and other's) work in. I've been building a lot of things ever since I started over a year ago, and on the whole I'm rather chuffed with them. Thing is though, due to the rather 'limited' graphics in SL, they never quite look real enough.

Know what I mean?

Anyway, a while back I was buying some furniture for another place I'd built, and I noticed that the creator had put a shadow underneath a table — and how much that added to the sense of realism.

"Cool!" I thought. "I could do that..."

And I started to whack prims with a shadow texture all over the place...

Using extra prims for each shadow though, is incredibly wasteful, so it occurred to me that I could draw the shadows directly on the existing surfaces...

"Well, DUH. That's what EVERYONE does doofus. It's called Texture Baking"

But anyway Back to the gallery.

I used Illustrator to mark out the floorplan, then worked out where I wanted to put lights and drew massive circles for each. Then I used various tools to cut out shadows in those circles — based on walls and stuff.

I brought that into Photoshop, and using copious amounts of Gaussian Blurs, various layer modes (Multiply and Screen mostly), and a fair bit of splashing around by hand with a large soft brush, came up with this¹...

Then I opened that up in GraphicConvertor, and using it's handy "Split..." function when saving, ended up with thirty six Targa images, all 512 pixels square, and all named rather handily so I could work out which floor-prim to stick them on.

And the result, as you've no doubt seen over the past few days, is this...

Thing is though, as you also might have noticed over the past few days, I've been getting all het-up about the strange lines that I've been getting on the edges of the prims...

It's been really bugging me There's not really much point in going to all the effort to make laborious floor textures if you're going to get nasty rendering artifacts like those, is there?

I thought it was because the prims were mysteriously not lining up properly (and it's true that there's a weirdly tiny difference in their z-positions, even though the numbers all match perfectly). But, a sudden realisation on my part, combined with an observation from Jessica...

Maybe its [...] the interpolation on the texture?

...made me realise what's going on.

Correct me if I'm wrong here, but when the SL client renders the texture on a prim, it does so independently of the other prims around it. It tiles the texture on all sides, then works out which bit to draw on the screen. So it sort of looks like this...

With me?

But because the texture is only 512x512, it blurs it slightly when it scales it up for the screen — so the edges bleed slightly. If it was a seamless texture, it would be no problem — but because one side is darker than the other, I get dark and light bits bleeding over the edges, giving me the unsightly lines. So, for example, I'll get a tiny bit of the bottom edge (dark) blurring into the top edge (light)...

Yes?

I'd thought that the way to get around this was to use a higher resolution texture. But as K pointed out, that would be a "lag bomb".

Thing is though, the answer's been staring me in the face

...

When I'm working in print, if I want to have a colour (or image, or text) going right up to the edge of the page, I have to give it some bleed. To make sure that when the guillotine slices the page, I don't get an unsightly white lines (because of inaccuracies), I give it some overlap as a fail-safe — usually about 3mm.

And it suddenly dawned on me that that's exactly what I needed to do with my textures. I needed to give them a little bit of overlap.

So, here's what I did...

For each texture, I take it — and it's eight neighbours — into Photoshop. I resize them all from 512 to 450 pixels (I'll explain why in a second), then I make the canvas size of the one I'm working on 1350 pixels square.

Then I reassemble all the neighbours around it, and trim it down (using Image > Canvas Size...) to 500 pixels — effectively giving me 25 pixels of 'bleed' all around the original texture.

Then I upload them into Second Life (have you any idea how many L$ I've spent uploading textures in the past couple of days? ), and whack them on the relevent prims.

Obviously, they don't line up properly — so I change the "repeats per face" of each to 0.9 — because 450 is 90% of 500 — and voila!

Beautifully aligned pre-baked textures, with no crappy artifacts on the edges.

/me bows

...

Once again, sorry if all that was a complete no-brainer. I suppose if I Googled a bit, I'd probably find out that a lot of other people use the exact same technique. But this is what I'm like I guess — I like working things out on my own

Right. Two floor textures done, seventy to go²...

¹ Astute readers will notice that the bottom right-hand corner of the final texture doesn't match the Illustrator image above it. This is because I am a numpty and got the floor-plan wrong initially

² You know, the whole process is very laborious. It's going to take me a fair few hours to get everything absolutely right — and if I decide to tweak the shadows at a later date, I'll have to do it all again. This would appear to be the perfect job for some kind of script...

Record Store Cats

My favourite, is Techno Tim — (Thanks Loz! )

If I'd Known It Was "Low Fat", I Wouldn't Have Bought It

I remember what I was going to write about today — my sleep patterns are totally fucked-up. This whole Weird Intense Dream Period™ is still going strong, although it's more like I have memories of having dreams, rather than remembering the actual dreams themselves at the moment.

The really strange thing about last night though, was waking up on the sofa at 6am, not quite sure about what was going on. It wasn't a Me Passing Out Because I Was Pissed™ thing — although I did get through a fair bit¹ — I remember quite clearly making a cup of hot chocolate and lying down "for a few moments" at some point in the early hours.

Somewhere at the back of my head there was the sensation of having just had some noctural adventure, but I was more focused on getting a pint of water down my neck, and refilling my bloodstream's nicotine levels, so, by the time I'd hauled my arse upstairs and got into bed properly, whatever dream it had been had long gone.

Anyway — the hot chocolate. I absent-mindedly grabbed the first jar that came to hand when out shopping the other day. As much as I like hot milky drinks, sometimes I just can't be arsed to boil up a pan, so I wanted to get some instant chocolate stuff.

I did toy with the idea of buying Sainsbury's Basics — being as it was about 50p rather than £1.50 — but decided (based on recent tuna adventures) that it would probably taste like shit.

Back at home, I was contemplating the fact that this jar I'd bought had a white lid — unlike all the other times when I've bought the stuff² when it's had a red one.

It was then that I noticed the "Less than 1% fat!" in big letters on the side of the jar.

Now in my experience, low fat stuff never tastes as good as its chubbier siblings, and to be honest I avoid it like the plague — in a similar vein to my avoidance of organic stuff³. As pathetic as it might seem, I rather enjoy the subtle naughtiness of buying 'bad' products.

But whatever. I never really found out what it was like.

I passed out before I even took a sip.

¹ But not tonight. No booze for me...

² That would be a grand total of "once", by the way.

³ One day soon I'll rant about organic products. Personally I think it's all just a big pile of crap myself. Having said that, I did get some organic double cream last night — but only because it was reduced to 10p. God, I'm such a fucking cheapskate...