Re: [Oiio-dev] udim

[Larry Gritz]

(CC'ing osl-dev because the fun part of this is on the OSL side.)


On Feb 2, 2015, at 11:52 AM, haggi krey <ha...@haggi.de> wrote:

> I am reading image files with OIIO in my texure system.
> Is it possible to use udim tiled textures from Mari, Mudbox or Zbrush with OIIO?
> And if yes, how? Do I have to implement the reading of the correct file name by myself in my texture file osl shader or are there any helpful procedures in OIIO?


You need to generate the texture name based on the coordinates:

umap = int(s);
vmap = int(t);
udim = 1001 + 10*vmap + umap;
filename = format ("%s%04d.tx", basename, udim);

look up texture (filename, s-umap, t-vmap, ...)

or, if your v's are all upside down, then 1.0 - (t-vmap).

BUT... if you are using this from OSL (I'm presuming, because I see you on the mail list there frequently), the repeated calls to create strings on every shade will be a bottleneck. But there's a special trick to make it super fast and fully constant folded!


shader
udimtexture (string basename = "",
float s = 0 [[int lockgeom = 0]],
float t = 0 [[int lockgeom = 0]],
output color Cout = 0)
{
#define NAME(i) format("%s%d.tx",basename,i+1001)
#define TENNAMES(j) NAME(10*j+0),NAME(10*j+1),NAME(10*j+2),NAME(10*j+3),NAME(10*j+4), \
NAME(10*j+5),NAME(10*j+6),NAME(10*j+7),NAME(10*j+8),NAME(10*j+9)
#define TENROWS TENNAMES(0),TENNAMES(1),TENNAMES(2),TENNAMES(3),TENNAMES(4), \
TENNAMES(5),TENNAMES(6),TENNAMES(7),TENNAMES(8),TENNAMES(9)

string filenames[100] = { TENROWS };
// The magic here is that the 'format' calls, since their parameters in this
// macro expansion are all constant, will be constant-folded at runtime, and thus
// the entire filenames[] array will become just constant memory that is initialized
// just once, NOT every time the shader executes.
// NOTE: if you expect more than 10 rows in v, adjust the above as needed.

#undef NAME
#undef TENNAME
#undef TENROW

int umap = int(s);
int vmap = int(t);
int udim = 1001 + 10*vmap + umap;
string filename = filenames[udim]; // MAGIC! just an array lookup, no format calls
Cout = texture (filename, s-umap, 1.0 - (t-vmap));
}





--
Larry Gritz
l...@larrygritz.com

[haggi krey]

Just wanted to let you know that this procedure works really fine. I extended it a bit to be able to use ZBrush/Mudbox style udims as well. Thanks again.