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Johnny
01-30-2007, 05:39 AM
I've been tangling for a few weeks with a large render requested by a client. by "large," I mean 8 feet tall, 6 feed wide.

this beast uses a bump map which is 300 dpi; fine for print, the orginal purpose of the image. But now that it's to be a large image, that 300 dpi bump has had it's pixels magnified, too, with the result of some nasty artifacts..

I am lucky in that I created this particular bump map in Illustrator, then rasterized in PS, so I can retrace my steps at higher resolution.

I'm tinkering with that map now at 1200dpi. things are what you'd call pokey, as that new bump map is way larger than the original.

I'm wondering if I ought to just cut out a square of that map, and have it tile in LW, but I'm not sure how to make this pattern line up the same way as in the original key to this; they want the giant picture to be just like the one in their brochure. Only GIANT.

any suggestions from those who've done this, or is it going to be by trial-and-error?

Also, if I just use the much higher-rez map, will the giant render take impossibly longer, owing to the increased number of pixels, or negligibly longer?

Thanks!

J

Lightwolf
01-30-2007, 05:48 AM
if LW can handle it (i.e. no swapping, the image fits into RAM), it should take negligibly longer.
As a bump map, greyscale will do (if it isn't already).

How many pixels os the bump, you final render and the part of the bump that is actually visible?

Cheers,
Mike

Johnny
01-30-2007, 06:06 AM
ahh..good to know..in my little test renders, I'm having to crank the bump values a LOT, such as 200 for texture amplitude, and 15000 for the Bump value in order fo that bump to show up with the same bump height in the image.

As for how much of that map makes it to the final image, I'd say about half.

the object is basically a sphere, and the camera can see appx half of it.

think I'm right to go with 1200 dpi in the bump map, or think I need to go higher yet? Problem is, this render takes about 30 hours to do, so, to see if the full size render is OK is not a quick thing.

thank you for the information.

J

Lightwolf
01-30-2007, 06:19 AM
Well, dpi has no meaning in 3D rendering, so I have no idea... if you mean 300dpi in relation to your 8x6 feet that would be... erm, darn english system, erm, 12 inches to a foot? - 28 000 pixels wide, right?

LW should be able to handle that, especially as a greyscale image. You could try UV mapping your sphere (spherically), cut off one side and apply half of the image to the remaining side.

Bump maps tend to need a different strength depending on the size of the underlying image map. The higher the bump res, the higher the strength you need.

Cheers,
Mike

Johnny
01-30-2007, 06:28 AM
well, right..DPI has no meaning, but what I have observed is that when a render is scaled way up, and the associated bit maps are not increased in their resolution, you get the result of the same number of pixels being used to cover a much larger area; nasty stairstepping results.

So maybe it's better to say "pixel density" than dpi when talking about 3D?

I'm smackin my head right now..it's one of those things I have known for years...I just whiffed on it when it came time to render this large image.

I think I'm going to be able to pull it off, tho...

J

Lightwolf
01-30-2007, 06:31 AM
So maybe it's better to say "pixel density" than dpi when talking about 3D?

How about just plain resolution? If you state the render size and the texture map size in pixels, it should be o.k.

Cheers,
Mike

Johnny
01-30-2007, 06:41 AM
works for me...

I've been tinkering with settings here, and I think I've gotten the map just about "there" with respect to the visual intensity I had before.

thanks for the tips...when I'm not under such deadline pressure, I'm going to play around with those ideas to get comfortable with them.

J

Lightwolf
01-30-2007, 06:55 AM
You're welcome. Well, if anything comes up, I suppose we'll be here ;)

Cheers,
mike