Grainy Texture Maps

Bittles

When I import a texture map to use as a bump on glass they always look grainy (in lighter areas). Why and Is there a way to create a smooth looking bump on glass using a texture import?

I've tried all sorts of textures ones I've created and ones that come with Carrara they all produce the same grainy results.

Headwax

hya are you rendering with antialias on "Good'?
on noneor 'fast' it makes textures look grainy
if you already do that have you turned down the bump setting in the texture room?
if you've done that then you can blur the texture in ps and see how you go
if its a procedural texture you can export the object and with it the textures as a jpeg (?) and then smooth it
and reimport it.
if it's a noise bump just reduce the brightness of the noise (from memory) in the texture room

3DAGE

HI Bittles :)

It also helps a lot if you can post an image of what you're seeing, ...then we can see it too :)
also a screen capture of your rendering settings and perhaps the shader settings.

You can adjust the "brightness" slider on texture maps to decrease the effect of a Bump map, but you can control the strength of a Bump effect on the "Top Level" of the shader list.

You can also use Carrara's built in shader functions , such as "Fractal noise" to create a Bump effect.

Bittles

On the neck of the bottle I am adding the bump to emulate a ribbed glass. Just for the sake of experiment I also tried 3DPaint. It added an interesting affect...I little better but still noisy, also offset so it added a thickness to the neck which I don't want.

In the end I used a natural bump waves and it looks cool I'll share later.

I do want to know what I am doing wrong with my bumps though. I do bumps on glass often and they never work correctly (grainy).

3DAGE

Your Bump is set to 250 (highest value), also, if you increase the size of your original image map, then the JPG compression may create a less grainy bump.// or if you save them as PNG or tiff that may help since these are less compressed.
But...
the bottom line here is that you're trying to create a modelling effect using bump.
Bump is an effect created by using light and shadow based on the bump map.

You may get a better effect using displacement mapping, although your model definition needs to be high enough to create the effect.

Bump, makes the model's surface appear bumpy. (but the model is still flat)
Displacement, will alter the shape of the physical model to create high and low areas. it deforms the mesh.

modelling the shape you want is always the best option (IMO)
although, on a Square bottle it's trickier if you want that effect on the full length of the bottle, but it should be easy enough to do that with extrusion and some rotation of the mesh.

Quick rough modelling example.