Friday, October 26, 2012

Perfect alpha cutouts

Getting something cut out of a background in SL perfectly can be difficult and frustrating- unless you know the trick of it.  Many people use the green screen trick, but you can have slight acid green bleed in your semi transparent areas, like hair whisps.

First requirement: you need to be able to take at least 2 completely identical pictures, aside from background colour (if there are flexis, you might want to turn them off after you've gotten everything into position, including your camera- Advanced menu>Rendering Features>Flexible Objects.  This CAN be optional, your flexis might not move so long as nothing moves...but then again, they might, depending on settings and conditions)- and you need to be able to change that background colour.

Take one picture with your background solid fullbright white.  Take a second picture identical but for the background being solid black.  Optionally, take a third (or more) with the colour a general match for the touchy alpha issues- a vague match for your hair, any semi transparent spots, etc.

In Photoshop, one of the layer styles is "Difference"- copy paste the black or white background over the white or black background, and set the top layer to that.  The image will be all black and white- the background will be white, everything else in the shot will be black, with perfect alphaed edges for cutouts.  Select all and shift-copy, paste that into a channel mask for the image, and invert it, so it's a white outline on a black background.  If your picture has shadows, you probably WILL still have to clean this up in minor ways, due to lines and shadows rendering differently on different backgrounds- make sure the places that should be solid are white, with no grey spots from shadows not rendering quite the same, and if you're taking larger than screen size, the line problem will have to be fixed.  If you're not taking it with shadows on, your mask is already perfect- aside from occasional minor shiny glitches, so you might want to zoom in on those and make sure they're all white!

If your white and black aren't quite 100% pure (which can happen, even with fullbright- especially with shadows and Windlight), you may need to adjust the levels of your mask ever so slightly pulling the end arrow in to the center a tad.  You should not need much, if you need this step at all- but you can have a slightly messy background mask that is mostly, but not 100%, transparent, under some circumstances (i.e. SL having a bad day).

Now, you can use this mask on your white background picture, your black background picture, or the picture(s) with the alpha colours.  This last option works best- if you have multiple problem spots, layer them all only showing the bits you need where to prevent the colour bleed (if you're scaling the picture down, the colour bleed may disappear, depends on how much of a stickler you are as to how much effort to put in here- it's going to be minor even if you just use the white background version).  If you have antialiasing on, there will be VERY slight bleed over the entire outline, so if you're wearing black, might want to do your cutout on the black background copy (black halo can also be less immediately noticeable than white, "shadows" rather than "halo").  But whatever you decide to cut out, use that channel mask for your selection or mask for your cutout!

Wednesday, September 19, 2012

Lining up LODs

This is a prime example of why a public jira is a VERY GOOD THING.  I would have been thoroughly perplexed by the entire problem AND would have taken much longer (if ever) finding the solution without the ability to browse preexisting jiras for this problem.  (I made an assumption that was incorrect, because it made logical sense to work that way, and no logical sense to work the way it does.  And computers are all about logic, right?)

The problem: you can upload multiple separate mesh objects at once into one linked object (this is great for, say, everything already being in the right place instead of having to line shit up!  Hooray!).  HOWEVER, when one does this and attempts to also upload your own custom LODs and physics shapes, the objects do not always line up!  This leads to lower LODs being wacky shapes, or just plain saying "nope, not doing it" if you don't have the same material setup on them all (texture faces). can upload multiple items and have them all in the right places in respect to each other OR you can have control over your LODs.  Not both.  (As an aside, the auto generated LODs seem to trim off the objects semi randomly- sometimes one object will get the LOD jacked down a lot, and the other will be barely touched, it doesn't seem to do it evenly.)

The Real problem: the collada exporters just randomly decide on an order for your objects in the file, not based on order selected or any other criteria over which you have control.  This definitely holds true for the blender 2.62 exporter- but it is not alone, other programs also have this issue.

The solution: reorder your collada file by hand.  First step, in your modeling program, before exporting, name all your objects useful names.  You need to be able to distinguish what is the same object in different LODs by name only, so keep that nice and consistent!  Export your collada file now that everything is named and easy to tell apart blind.  Use a basic basic text editor (WordPad works perfectly), open up your dae file.  It's a bunch of xml code in there, nested <type> <subtype>.  Now, you're on your own here a bit, because collada files vary WILDLY in what they call things and how they're ordered.

There's going to be material data in there (probably), which you can just skip by.  You're looking for geometry or something similar.  In my current exporter, I'm looking for <geometry id="object_name" name="object_name"> (Note: those names don't have to be the same, and they are things you set, so you should know what names you're looking for).  There will be a bunch of nested attributes, and then a close geometry tag, and then another open tag with a new name for the next data block.  Find out what order your data blocks are in there!  Then open up another LOD file, scroll down to the same geometry blocks, and reorder each entire block into the same order as the first file- repeat for all LODs (the ENTIRE block needs to be moved, from start to end tag for an object).  Save the newly reordered files (just as text, don't let it do anything fancy, don't rename from .dae).  Now they should line up so the objects agree across LODs instead of randomly assigning!

Saturday, September 15, 2012

The Arcade

tiny arcade planet

It's been forever since I've posted anything here, and even longer since a tourism update.  I want to do those more often (I've been preoccupied with moving and a broken thumb and too many events and an occasional fashiony blog- I haven't BEEN much of anywhere a lot lately).

The Arcade

This time, I'm cheating.  Because, you see, I got in early because I'm a participant, so I have pictures that aren't crammed full of eleven jillion people (or, you know...30.  whatever the avatar limit is).  The Arcade!


Aside from the actual, you know, the spendy money on awesome things reason to go, the venue is amazing.  It's an enclosed skydome, with an entire planned environment separate from everything else.

looking around

It is, as you can probably tell from looking, pretty much 100% mesh.  Mesh really does open up possibilities that were unavailable previously- sculpts helped (a LOT!), but mesh is much more flexible with efficiency and texture management.  (I'm also lucky/spoiled and can run with shadows on all the time on this computer, so I do, oh, how I do.)



sit here, trust me!

You super duper want to sit on a donation kiosk, whether you toss any money their way or not. Make sure you've got default camera (hit escape a couple of times).

the hall

the roof

Sunday, February 19, 2012

New Math

With meshes, we now have 2 ways to calculate prim count, old math (one prim = one prim), and new math (one prim = however many land impact prims depending on a number of variables). Any linkset linked to a mesh always uses new math (just one mesh in a linkset will force new math for the entire linkset, always). But you can choose to use new math on a linkset of traditional and sculpt prims as well.

But do that with care! There are reasons to do it, and reasons not to. Biggest reason to? In new math, a single prim can count as HALF a prim in a linkset, so one linkset of prims can be half the number of actual prims. Link six boxes and use new math? 3 land impact prims. (Note: this always rounds up. 5 prims will also be three prims, 7 prims will be 4). THIS ONLY APPLIES TO STATIC PRIMS. THEY CANNOT BE SCRIPTED OR PHYSICAL. It's a bonus modifier we get applied to "simple" prims, those that impact the server less.

However, new math is not straightforward like old math. There are 3 variables, and you have to figure out how to juggle them. Some people are just telling people to set entire linkset to Convex Hull and watch the savings: but if you don't have the right things in your linkset, your prims will count as MORE, and you may not be able to walk into your buildings anymore!

There is an easy way to find out what things will cost, and if it's worth trying (AND how to fix the not being able to walk into places problem). Click on the "More info" link to find out what your object will cost (it can take a bit to calculate though!):
That will bring up this second menu with all your infomation. The thing I currently have selected is 3 prims. The three things that make a difference to us for prim count are Download, Physics, and Server. This Features tab, with the Physics Shape thing? That's where you need to set Physics shape to use new math. If all prims in a linkset are traditional prims, and use Prim physics, that linkset will use old math. If ANY prims in the linkset are set to either of the other two options (Convex Hull or None), the entire linkset will use new math- this is how you set non mesh prims to mesh math.

Download is how complicated the object is. It calculates by number of faces and size, complicated prims have more faces. Aside from replacing prims with less complicated ones, or shrinking prims, or removing complicated prims from the linkset entirely, we can't get this number any lower. Sculpts are a MINIMUM of 1.3 Download, even tiny, even with faces thrown away in the sculpt map (that, in fact, doesn't seem to have any impact to sculpt calculation ever- sculpts seem to have a flat calculation, regardless of the sculpt). And they go up from there. Linking 2 sculpts together will become 2.6- which will count as THREE prims. So only use sculpts with new math if you can balance the cost with other prims! Sculpts and toruses and spheres and tubes- anything other than boxes and prisms (and how often do you use a prism?)- can cost you, depending on size and complexity, they can cost too much. Boxes are cool. Boxes are 0.1, even at 64mx64mx64m, hollowed (even circle hollowed) and cut! (NOT twisted. Twisted ads a very substantial amount more to it, because it requires many more faces for the twist.) So, say you have a linkset with a bunch of boxes and a sculpt? You may find you can link that together and use new math and prim count goes down. But you may not.

Physics is where you can really play with your linkset cost. Simple physics (boxes! But not as much cutting or hollowing this time!) cost very little. Complicated physics, especially hollowed or cut things, even boxes, start costing. You can reduce physics cost by making things Convex Hull, but that makes them VERY simple: you will not be able to walk though hollows or cuts, and the actual outer shape beyond that may not be what you expect (it's not straight up bounding box all the time, but sometimes it is). You can reduce physics further by setting SELECTED PRIMS IN THE LINKSET to None. The root prim CANNOT be set to None. Physics set to None works like Phantom: so you can mix Phantom and non Phantom prims in a linkset this way too! Hollowed or cut prims for doorways may have to be set to None (you can set them to Prim so long as the rest of your Physics allows for the calculations). Many sculpts you may want to set to None to take them out of the Physics calculation, as well as not having their physics get in the way. You can set all the prims in the linkset individually to your choice of the three options, and you may need to! These example prims? I need to set my physics to Convex Hull or None to bring down my cost before I use new math, or not use new math at all, as well as linking them together (in practice? The base had to be set as Convex Hull, AND all the linked prims had to be set to None, before I could get the Physics low enough to see enough savings to actually lower the prim count. They are a sculpt and 2 cut tubes, so, complicated- but those cut tubes actually don't cost all that much at this size, so I can get away with it, so long as I don't need proper physics collision).

The last variable here is Display. That will NEVER be less than half the number of prims in your linkset. In this case 3 prims, divided by 2, equals 1.5. This is an unscripted unphysical linkset, so I get the static bonus. If this is equal to the number of actual prims, it's not worth trying to use the new math, because you won't see any savings!

The largest of these three numbers will always be the one used. The land impact number is rounded by linkset, 1.5 will be 2 land impact prims, but 1.4 will round down to 1.

A lot of land impact can be saved if you are smart in how you juggle your physics- and in what you link together! But that large sculpt? You may want to unlink that to leave it using old math and make sure you select it too before you move your thing.