texture filter?

[sharktacos]

Is there a man page that describes the various options for the new texture filtering attribute?
What is the default behavior without this attribute?

[Zdravko]

The additional texture filter attributes works similar to the Maya native texture filter but they give you better control and predictable results.
Here you can find description for some of the option, as they are also used in the Texture filter for Substance nodes options:
http://www.spot3d.com/vray/help/maya...htm#tex_filter

[sharktacos]

The additional texture filter attributes works similar to the Maya native texture filter but they give you better control and predictable results.
Here you can find description for some of the option, as they are also used in the Texture filter for Substance nodes options:
http://www.spot3d.com/vray/help/maya...htm#tex_filter

Thanks for that link. Let me sum up what I am understanding, and then ask some questions based on this:
There are 4 options under the texture filter:

nearest
smooth
smooth w/ mipmaps
SAT

The manual describes these as:

• Nearest - the nearest texel from the map is taken, without any interpolation;
• Bilinear - the colors are computed with bilinear interpolation from the texels;
• Mipmaps - pyramidal MIP map filtering is used to compute the texture color;
• SAT - a summed area table is used to compute the texture color.

Then there are 3 smooth methods below these:

bilinear
"bicibuc" (I am assuming this is a typo and should really be bicubic),
biquadratic

I found a description of these here :

• Bilinear - the image values are interpolated from four pixels in the bitmap. This is the fastest interpolation method, but the result is not continuous (non-smooth) and may produce artifacts when the map is used for displacement or bump mapping.
• Bicubic - the image values are interpolated from sixteen pixels in the bitmap. This is the slowest method, but the results are smooth without too much blur;
• Biquadratic - the image values are interpolated from nine pixels in the bitmap. This method is faster than the Bicubic interpolation, but may smooth the image too much.

It says here that the default (in Max) is to use Bilinear for HDR and EXR images and Bicubic for all other formats. It seems however that the Maya default is bilinear all formats.

QUESTIONS:
1) Mipmaps: My understanding is that mipmaps require a special format. So if we have a jpeg texture and select mipmaps (the default selection here) or SAT (a varaition of mipmaps) will it:
a) auto convert the jpeg into a mipmap on the fly (if so does it store these somewhere like mental ray does)?
b) do nothing since it is not mipmap format and revert the default smooth method? (I think it is doing "b")

The big question here is whether there is a way to have texture maps auto converted to mipmaps in vray, like mental ray does. Last I read, you had to use img2tiledexr to manually convert them all to a special multi-tiled EXR in the shell which is kind of a hassle. Has this changed?


2) Smoothing Methods: How do the smoothing methods work in conjunction with the texture filter type? My understanding is that they only apply when it is set to "smooth":

nearest - "without any interpolation" so no smooth method is used.Smooth method drop-down has no affect and should be greyed out.
smooth - bilinear, bicubic or biquadratic. The default is bilinear.
smooth w/ mipmaps - Using smooth (above) + mipmaps.
SAT - Using mipmaps with SAT smoothing, so the smooth methods do not apply since it uses SAT instead. Smooth method drop-down has no affect and should be greyed out.
Could someone verify the accuracy of this?

3) Texture filter Off: As Vlado explained, it is important when using transparency to set the filter to "off" to avoid extremely slow render times. Even if it is set to "off" in the Maya texture filter, Vray will still apply a filter to it. We therefore need to override this with the vray attribute. However I do not see an "off" option here. So how do we turn off filtering in this case?
[Edit: This can be turned off globally in the Render Settings, however in most cases one would not want to do this globally, but rather only for specific transparency maps as needed]

Thanks!

[Zdravko]

do nothing since it is not mipmap format and revert the default smooth method?

The mipmaps option won't change the .jpg images, as you suggested.

you had to use img2tiledexr to manually convert them all to a special multi-tiled EXR in the shell which is kind of a hassle.

For now you would have to use img2tiledexr tool to convert to OpenEXR file, V-Ray can't do that on the fly.

2) Smoothing Methods: How do the smoothing methods work in conjunction with the texture filter type? My understanding is that they only apply when it is set to "smooth":

Yes, you are right they are only applied if you have the texture filter set to Smooth mode.

However I do not see an "off" option here. So how do we turn off filtering in this case?

To disable the filtering you need to set it to Nearest.

I hope that helps.