Mantra Swizzle Coordinates (Direct X/Open GL Normal)

[kremiansky]

Hi all,

 

Not quite sure which coordinates by default Houdini Mantra uses for normal map, is it +X +Y -Z? I'm exporting Open GL normal maps from Substance Painter which were working like a charm in Maya, but seem not to be working correctly in Houdini?

Here's the comparison for other softwares.

Thanks!

Software	Red	Green	Blue
3ds Max	X+	Y-	Z+
Blender	X+	Y+	Z+
CryENGINE	X+	Y-	Z+
Maya	X+	Y+	Z+
Modo	X+	Y+	Z+
Source	X+	Y-	Z+
Toolbag	X+	Y+	Z+
Unity	X+	Y+	Z+
Unreal Engine	X+	Y-	Z+

[schiho]

Too less information to solve your problem from my standpoint, do you have an example file?

[jimmay]

The first thing to do is make sure that the Texture Color Space is set to Linear, for images where "flat" or unperturbed is defined as 0.5 float (or 127/128 in 8-bit channels).  I've had PNG's bite me that way before, where the file had a nonlinear gamma or something, and you just get "wrongness".

I'm fairly certain that Houdini uses +X +Y (on my Displacement Texture VOP node, both "Flip" checkboxes are off.)  This is, in terms of the appearance of the channels in Photoshop, "lit from the right" in X (red) and "lit from the top" in Y (green).  I can't speak to the Z blue channel, as its effects are really subtle, so if the blue channel were "wrong" in the textures I've been using, I wouldn't necessarily know by looking.  My current normal maps use 1.0 (255) for unperturbed, and range down to 128 for maximum perturbation, though mine are derived mine from the X and Y channel.  I would expect it to be +Z if for no other reason that it would be arbitrary to make that one -Z just to be contrary

I'm also assuming tangent space normals here.

 

Edited June 15, 2017 by jimmay

[kremiansky]

On 6/16/2017 at 0:48 AM, jimmay said:

The first thing to do is make sure that the Texture Color Space is set to Linear, for images where "flat" or unperturbed is defined as 0.5 float (or 127/128 in 8-bit channels).  I've had PNG's bite me that way before, where the file had a nonlinear gamma or something, and you just get "wrongness".

I'm fairly certain that Houdini uses +X +Y (on my Displacement Texture VOP node, both "Flip" checkboxes are off.)  This is, in terms of the appearance of the channels in Photoshop, "lit from the right" in X (red) and "lit from the top" in Y (green).  I can't speak to the Z blue channel, as its effects are really subtle, so if the blue channel were "wrong" in the textures I've been using, I wouldn't necessarily know by looking.  My current normal maps use 1.0 (255) for unperturbed, and range down to 128 for maximum perturbation, though mine are derived mine from the X and Y channel.  I would expect it to be +Z if for no other reason that it would be arbitrary to make that one -Z just to be contrary

I'm also assuming tangent space normals here.

 

yep, tangent space normals, should've mentioned that, although I think object space normals work with same system.