Is there anywhere I can find a comprehensive list of what tangent basis various apps use for rendering normal maps? If not, could we create one here?

For instance, I know 3ds Max uses +X and -Y, which is different from some other apps. With all the programs I use, it can become slightly confusing trying to remember if I need to flip the green channel or not. Any insight is appreciated.

I think it would be wiser to point out how the most common engines handle that.
Every program for rendering normal maps lets you decide how you want that.

Maya renders +y by default (right handed), but you can change this behaviour as you go. However tangent basis != handedness which is what you are looking for in your post.

Good point, tangent basis isn't really the same thing as handedness. I guess I had assumed that the handedness was derived from the tangent basis. Or maybe I'm just completely off track.

(If this is maintained, a simple "Software - Orienation" list would make life easier. Also, a Wiki Page might make more sense..)

AFAIK, xNormals uses the same basis as Max; if you're saying Max is +X/-Y, then xNormals is the same thing. I believe the Photoshop plugin defaults to the +X/+Y. So,

Max : +X, -Y
Maya: +X, +Y
xNormals : +X, -Y
Photoshop nVidia Plugin : +X, +Y

Like m4dcow mentioned, there's a way to change this setting in each of these programs; this is mostly helpful in making sure your settings match across your pipeline.

Some other good reading on how the Tangent Basis is calculated in several different packages (in case your developer starts shaking his fist at you): http://www.polycount.com/forum/showthread.php?t=84616

Originally Posted by SeanEG

I guess I had assumed that the handedness was derived from the tangent basis.

If Handedness = Polygon Winding direction, then I believe it depends. Our software derives tangents from the winding direction, but I guess that's not always standard, which freaks my devs out whenever they run across it (sort of like calling the sky Green or something).

It's not that simple. The axes thing is insignificant compared to the other differences between apps in calculating normal maps

what Perna said.

like, if i remember rightly, i read on the UDN site some time that they used an in-house app for generating their normals (makes sense), but that means that potentially there is no app on earth that would generate normals the same way Epic do.

which is of course, a problem.

edit:
http://udn.epicgames.com/Three/Impor...hTutorial.html

apparently the tool they used is called "SHTools".

... sure, but assuming you're not using in-house software, it's possible to take a Normal Map generated in xNormals (or whatever) and view it correctly in Max (or whatever). A Tangent-Space Normal Map relies on accurate normals, tangents, and axis inversion all working in unison. Assuming you've got the first two, the second is an easy toggle; I think the OP was just asking for a list of what to flip to and when.

Alternatively, if, say, Maya tangent generation differs from Max tangent generation, then that would still be a good thing to have a list of somewhere. A list of tangent/inversion compatibilities.

Originally Posted by almighty_gir

edit:
http://udn.epicgames.com/Three/Impor...hTutorial.html

apparently the tool they used is called "SHTools".

I've used SHTools a long time ago. We don't use it anymore even for unreal games.

I believe it was developed when epic was first using normalmaps because you couldn't bake normalmaps in max. It was that long ago.

I had to use that, sucks ass, there's no antialiasing.

Off the top of my head...

Max X+Y-Z+
Maya X+Y+Z+
ZBrush X-Y+Z+ (not 100% sure)
UDK X+Y-Z+
Marmoset X+Y+Z+
IDTech X+Y+Z+
CryEngine 3 X+Y-Z+
Blender 2.4x+ X-Y-Z+
Blender 2.57+ X+Y+Z+ (now uses mikktspace by default)
xNormal X+Y+Z+ (also uses mikktspace by default)
CrazyBump X+Y+Z+
Nvidia Filter X+Y-Z+
PixPlant X+Y-Z+
nDo2 X+Y+Z+

Feel free to correct them, if i got any wrong

While the axis that different programs use are insignificant when compared to the other complications, i still think it would be a good idea to get these on the Wiki, as when i was first starting out it used to drive me crazy trying to find them all out.

you forgot ue3/udk X+Y-Z+

@passerby:
Fifth row, take a good look and try again ;)

blah im stupid today

I updated my post to include CryEngine 3, which uses X+Y-Z+

We seriously need a standard...

Inverting the Green channel results in a percieved increase in quality for compressed normal maps, this is why it's all over the place.

Also...isn't tangent basis something completely different?, isn't this swizzle coordinates?.

Right Scruples, my question is, why are you guys worried about the XYZ negatives and positives if tangent basis doesn't mean that at all? For me tangent basis always meant the amount of angle the vertex normal converts the tangent of the surface, not the RGB info on the map. Am I wrong here?

We also had a long conversation about this not so long ago, comparing different tangent basis inbetween softwares here: http://www.polycount.com/forum/showthread.php?t=68173

Yeah, tangent basis wasn't the best term to use when creating the thread. I had assumed the "handedness", or direction of the Y axis, was derived from the tangent basis. Mods can feel free to change the thread title.

Originally Posted by Scruples

Inverting the Green channel results in a percieved increase in quality for compressed normal maps, this is why it's all over the place.

Not quite, try again.

Also...isn't tangent basis something completely different?, isn't this swizzle coordinates?.

Swizzling (as it applies to images) is swapping color channels around when exporting said image, such as DXT5NM

@metalliandy, Blender pushing for a tangent space standard is pretty cool

Isn't tangent basis how you calculate the bitangent/binormal and tangent components that come along with the vertex normals?

Originally Posted by kodde

Isn't tangent basis how you calculate the bitangent/binormal and tangent components that come along with the vertex normals?

that was my understanding. folks seem to be mixing it up with every other normal map buzz word.

Originally Posted by Scruples

Inverting the Green channel results in a percieved increase in quality for compressed normal maps, this is why it's all over the place.

Also...isn't tangent basis something completely different?, isn't this swizzle coordinates?.

The direction of the axis has absolutely no effect on the quality of the results you get. The only reason there is a difference, is because some shaders are coded to use a preferred set up

Originally Posted by bugo

Right Scruples, my question is, why are you guys worried about the XYZ negatives and positives if tangent basis doesn't mean that at all? For me tangent basis always meant the amount of angle the vertex normal converts the tangent of the surface, not the RGB info on the map. Am I wrong here?

We also had a long conversation about this not so long ago, comparing different tangent basis inbetween softwares here: http://www.polycount.com/forum/showthread.php?t=68173

Originally Posted by SeanEG

Yeah, tangent basis wasn't the best term to use when creating the thread. I had assumed the "handedness", or direction of the Y axis, was derived from the tangent basis. Mods can feel free to change the thread title.

Yea Axis and Tangent space are different. I posted the axis values, because i knew what Sean meant and its good to finally get a list of these down somewhere
He corrected himself in post 4 too

@Sean, maybe message a mod to change the thread title and edit your first post?

Originally Posted by throttlekitty

@metalliandy, Blender pushing for a tangent space standard is pretty cool

Yea, its a move in the right direction