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View Full Version : Bump issue - can't get it sharp and clean


bunnyld
09-29-2006, 04:08 PM
hey all

i'm new to xsi
making my self challenges and this days i'm learning about the lighting and materials of XSI

There is a strage problem when i'm add a bump to a texture on the floor
it looks like the original texture twice instade of Bump illusion
(what i did is to check the V next to BUMP on the color texture)

take a look

http://ramot-hefer.britannica-ks.com/users/www/565/s1.jpg


http://ramot-hefer.britannica-ks.com/users/www/565/s2.jpg


http://ramot-hefer.britannica-ks.com/users/www/565/s3.jpg

this next render I tried to use a separated BUMP map which gave me a similar low quality bump result: (used black and white image based on the original texture)

http://ramot-hefer.britannica-ks.com/users/www/565/s4.jpg


in this last render I play with the step of the bump. set ot higher then 0.001 as default, to 0.5 and it all go rong exept of some area i maked .. that came out very good

http://ramot-hefer.britannica-ks.com/users/www/565/s5.jpg

I am very confused ...
how can i get this bump work right?
in ather apps you can just add the bump texture and it works fine..
can it be a bug?

i use ver 4.0
Geforce 2 gts pro with latest drivers installed, win xp pro SP1 (32b)

thaks for reading .. and sorry for bad english

mocaw
09-29-2006, 06:20 PM
Setting up bump maps the "correct" way in XSI can be hard at first, but it has its benifits. Check the help and search the web for it. If you want what many other apps have try downloading this:

http://shaders.moederogall.com/zbump6.zip

Ben has several other great shaders you might want to check out as well.

Felipe
09-29-2006, 06:21 PM
Hi there,

Did you freeze the scale transformations? it should read 1,1,1 for x, y and z. This could be a problem when using bump.
When using an image as a bump, the step value should be 1/(size of image in pixels). For instance, if your image is 1024x1024, use 1/1024 for x, y and z.
Use the script editor to enter those values if you can't type them in.

Cheers,
Felipe

mocaw
09-29-2006, 08:59 PM
Hi there,

Did you freeze the scale transformations? it should read 1,1,1 for x, y and z. This could be a problem when using bump.
When using an image as a bump, the step value should be 1/(size of image in pixels). For instance, if your image is 1024x1024, use 1/1024 for x, y and z.
Use the script editor to enter those values if you can't type them in.

Cheers,
Felipe

Thanks for that 1/X tip. In the XSI production DVDs they go over the step values, but the person doing the demo just kind of guesses (maybe they were using a procedural). They do go on to speak on how it works in theory. I don't remember them giving such a definitive answer though- thank you it really helps!

Felipe
09-29-2006, 09:13 PM
I've got that tip from the production DVDs, he does explain about how bump works in great detail using procedurals and images. You probably missed this part :-)

Stoehr
09-30-2006, 12:21 AM
Could you upload the scene file, and we could take a look at it?
My first thought is, don't plug the bump map generator into the bump port of the illumination node. Instead, plug the bumpmap generator into the bump port of the material node.

mocaw
09-30-2006, 03:14 AM
I've got that tip from the production DVDs, he does explain about how bump works in great detail using procedurals and images. You probably missed this part :-)

Ah, I guess I should watch most of those videos again! I was stupid (when am I not) and tried to watch them all back to back before I'd used XSI for more than a few hours. I'm sure a lot more would sink in now...

bunnyld
09-30-2006, 09:03 AM
ok here is what i did

first i connected A bump generator map to the material (not to the shader)

but still the bump looks bad

so i did as you guys said and freeze the floor object by:

transforum -> freeze all transforums

and it fixed the low quality problem and the step of the bump

but why? what is this freeze?
thanks all for the help

ho.. and about that dvd tutorial, what it tech?

ruisantos
09-30-2006, 10:29 AM
Hi!
what i usually DID was to divide 0.001/number of repeats,in the script editor,like this:

SetValue "grid.Material.Bumpmap_generator.step.x", 0.001/40
SetValue "grid.Material.Bumpmap_generator.step.y", 0.001/40
SetValue "grid.Material.Bumpmap_generator.step.z", 0.001/1

but that is a waste of time,and a workflow stopper...so,
Thanks to a script writen by Guillaume Laforge,all that procedure is a lot quicker

You just setup your bump as always,and then just press the "Thegoodbumpstep" button
and it sets the step values correctly for all the bumps in the scene.

you can find it here:
http://www.vol2nuit.fr/guillaume/script_Render.htm

you can make it a button if you whish...

Rui

bunnyld
09-30-2006, 10:35 AM
yeah a button can be great

but how do i insert the script into a button?

ruisantos
09-30-2006, 10:46 AM
Ok...

Open XSI,open View->Toolbars->scripts(user)... Press F5...pick the scriptfile...drag and drop into the scripts window...

Give it a small name...and that's it.

but you should read the manual..the way you're connecting your bump map is not correct...
you should simplify your rendertree,
just use the bumpmap texture with a bumpmap generator and connect it either to
the shader or the material node.

Rui

ruisantos
09-30-2006, 10:49 AM
opps!! not press F5...but press 5..
sorry!

bunnyld
09-30-2006, 11:20 AM
I gonna try it right away.. =) thank you

this images render with 1 infinite area light from the front and a plane with low intensity at the back, using FG

now what i did is switch the infinite light to a point light
but now the render take far more time

maybe time 3 then it was with infinite light
i don't really see a huge different .. wierd

Is point light preduce better quality ?

(both lights was areas)

mocaw
09-30-2006, 07:01 PM
OK, so here is the question- if all that is ever needed is this 1/X use of bump step why isn't it just automaticly set that way? Though it is often not as high of quality, I find adjusting the step outside the "perfect" areas slightly allows me to tweak my bump map to render more quickly. Doesn't it control the amount of sampling in a way for the bump map? Is this not the reason that a user can adjust it?

I know the manual states:

"If necessary, adjust the Step values. This defines the UV offset within which the shader evaluates the object surface to determine the surface orientation.

The larger the texture used, the smaller the Step value should be. Typically, the Step value should be set in the 0.001 to 0.05 range. Larger values produce low quality bump maps with large numbers of artifacts."



Just wondering if anyone else sets the step outside of the optimal area for certain reasons (such as render speed etc.)...

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