if there any way to have no filtering on the texture map when used in surface shader ?

circusmonkey
if there any way to have no filtering on the texture map when used in surface shader ?

If you're using VOPs or VEX, it's easy.

1. Use the colormap() function (Color Map VOP) instead of the texture() function (Texture VOP), as the texture() function listens to shading derivatives and colormap() does not.

2. Or, in Texture VOP, set the filter to “Point” filtering.

I don't know if they have changed it but in H8 you still get some filtering even doing that because of the micro polygons and post blurring filters.
If you want absolutely no filtering at all, make sure you render into a deep raster channel with a unit box filter. If you render normally you have to change the pixel filter, the sampling, the dither channel, and render with raytracing.
It's unusual to want no filtering anywhere, its probably just me but those are the issues I've found in case you need the same thing….

Yes its just I do not want filtering on the texture maps as I am rendering 720 x 576. I find you just loose to much detail otherwise

circusmonkey
Yes its just I do not want filtering on the texture maps as I am rendering 720 x 576. I find you just loose to much detail otherwise

What about increasing the shading quality/rate from 1 to 2 (or 3). Or use a sharpening filter like sinc?

You can also try and change the filter on the ROP.

Here's an OldSchool Blog on just the thing with lots of texture mapped teapots.
http://www.sidefx.com/index.php?option=com_content&task=view&id=725&Itemid=216 [sidefx.com]

Jeese two plugs to my blogs tonight. I feel like a used car salesman…

Btw, using these same filters in the Texture VOP has the same/similar result on texture lookup. All but the min/max min and min/max max. For that you need to use the Color Map VOP as outlined above but that is highly not recommended. You WILL get aliasing issues.

Actually anything that is “crisp” at low resolutions (1k - 2k) will have aliasing issues when things move in and out from the camera.

Rayes based micropolygon renderers (RenderMan, Mantra micro-polygon mode) tend to have a soft-ish look. To get crispness try the different filters and combine that with higher shading quality levels as Jim mentioned above.
A shading quality of 1 results in your geometry being diced in to approximately 1 pixel sized grids. Higher levels cause your geometry to be subdivided even finer. A value of 2 will result in geometry cut up in to 1/2 pixel sized geometry. So, very high levels of shading quality ( 3, 4 and above) will result in a tremendous amount more geometry with the same number of shader calls. Not what you want to do but sometimes you need to. Generally not for texture maps though.

Wolfwood

circusmonkey
Yes its just I do not want filtering on the texture maps as I am rendering 720 x 576. I find you just loose to much detail otherwise

What about increasing the shading quality/rate from 1 to 2 (or 3). Or use a sharpening filter like sinc?

I agree with Wolfwood - this is what you want if you want better texture sharpness (with the Micropolygon rendering engine). Increase your Shading Quality and you'll see all greater detail appear. You'll still have correctly filtered textures but the higher sampling rate should bring out more detail.

Usually you only want to really start messing with point-filtering and sharpening filters if you're rendering either technical images or stills for print. For moving images, (especially for slow moving cameras or objects) you want to still use filtering in order to combat aliasing and properly represent highly detailed textures stuffed into one pixel.

Thanks for the input guys …… No wonder Ive bought houdini with all this advice floating around

Rob

Jason, do you stick with the default Gaussian 2x2 in both texture filtering and ROP output filtering for all your renders?

jeff
Jason, do you stick with the default Gaussian 2x2 in both texture filtering and ROP output filtering for all your renders?

We use the default texture filtering and the default pixel filter most of the time, yes.