Output not affecting Bump?

[Stroker]

Did a little more playing around, and I'm not exactly happy with my findings.

Output has no affect on maps that contribute directly to the final map. For example, Noise in Bump and Output in the Noise does nothing.

I don't like this behavior. Suck!

Output does affect, however, portions that *composite* the final map. Let's say you are using Mix and have Noise in the Mask slot. Well, Output in the Mask (being Noise) does work.

I still can't help but wonder if I'm missing something. If I have to, I'll resort to baking, but that's a last ditch.

[EricChadwick]

The Bump Amount spinner is the only one that affects, well, you know. The others have no affect on maps in the bump channel, except as you found out, if they are masks or other maps that do not directly contribute to the bump itself.

Have you read the "Output Rollout" section in the help file? They don't say this really, but there is some good info in there.

[Stroker]

Yeah, I caught the blurb about Bump Amount, which almost seems applicable (at a glance).
Something like, "If you have Diffuse and Bump instanced, then use this because it's independant."
But I haven't seen hide-nor-hair mention of Output having no direct affect on bump.

This really sucks.
I'll try to find a hack around tomorrow.
I don't want to resort to baking, but that's what it's looking like right about now.

Thanks.
I'm off to weep.

[EricChadwick]

Why not just fiddle with the main cellular settings instead of messing with curves?

[Stroker]

Because output curves are good for modifying for more things. Yeah, that.

In the case of cellular, I was going for flaking paint and rust things. Cellular is a decent enough base, but it needs some creative curving for the fit that I want(ed).
Why, oh why? :sniff:

Taking your suggestion, I did try to get cellular's colours to get close to what I'm going for. You know, high, low and middle colour dohickies. Guess what? Even that didn't work. Cellular looked just like cellular dispite the colour changes in the colour thingies.

I'm resigned.
Guess I'll be baking and using other hack arounds.
The really suck part is that I was gearing up to write a buttload of tutorials about this junk.

[EricChadwick]

Hehheh, best way to learn! Post links to them when you're ready, I'd like to learn more.

This bump issue was discussed last summer on the Discreet forum, about how the bump channel works in 3ds max. The thread has probably scrolled off by now, so here's what I saved of it...

====================
Topic: How do bump maps work? (no, really) (1 of 8), Read 189 times
Conf: Rendering Materials & Lighting
From: Tim Chang
Date: Sunday, August 24, 2003 03:23 AM
Originally Posted 22-Aug-2003 20:35

Hello All

The usual explanation you get re. bump maps is that they "perturb" a face's normals. I used to take this as read but now find it somewhat lacking.

Surely, perturbing a normal is what the 3-part data (commonly referred to as RGB) in a normal map does? As far as I can gather, a b&w bump map can only provide a scalar quantity.

However, even if I'm right so far, the explanation must go deeper than that because the scalar value provided by a bump map pixel seems to also depend on the bump values of other pixels around it. To elaborate: a bump map that's completely black gives the same effect as a completely white map, or completely grey map. ie, there's no relative difference between one pixel and the next, therefore no bump effect.

Can anyone confirm that my thoughts on this are correct?

TC
(Completely bereft of a formal CG education)

------------------------------
Topic: How do bump maps work? (2 of 8), Read 153 times, 2 File Attachments
Conf: Rendering Materials & Lighting
From: Tim Chang
Date: Sunday, August 24, 2003 03:17 AM

Okay I've left that little puzzler behind. Besides, what I really wanted to play with were normal maps. Someone told me there's a normal map plugin that goes into the bump slot of a standard max shader. Can anyone tell me whether or not this functions as a proper normal map in the renderer, or is it just for viewing purposes in the viewport? I think that in order to render, the plugin must alter the workings of the Bump Slot so that the map inside it functions differently (as a normal map, not a bump map. I don't believe the two are interchangeable).

The big picture is that I'm interested in hi-rez object renderings from low-poly proxies. Normal maps are one way of doing this, but I had a poke around Mankua and found the free TLunwrap and got distracted with that. In case anyone's interested, I found a quick n' dirty way of using it to create displacement difference maps between a hi-poly object and a low-poly stand in. Basically, I used depth fogging (a black fog render of each TLunwrapped object, with the objects given a luminous white material), and then using photoshop to create the difference between the two renders. This then becomes a standard displacement map.

Here are some pictures to demonstrate. I used a simple cylinder, the hirez version being detailed up with a bit of greebling. Rendering was done with max's standard scanline. I imagine a later-technology renderer (like VRay) would do a much better job.

(I just found it interesting.)

:o)

TC


MAXTLUNWRAP.JPG (160KB)

------------------------------
Topic: How do bump maps work? (no, really) (3 of 8), Read 130 times
Conf: Rendering Materials & Lighting
From: Alex McLeod
Date: Sunday, August 24, 2003 07:35 PM

>Surely, perturbing a normal is
>what the 3-part data (commonly
>referred to as RGB) in a
>normal map does? As far as I
>can gather, a b&w bump map can
>only provide a scalar
>quantity.

You may have found that certain black & white maps don't produce bumps at all. Try using any texture to mix between black & white in a Mix map, for example - absolutely no bump effect.

This is because textures have to explicitly generate a bump value in order perturb the normal at render-time, which as you've rightly surmised is a point3 (vector) value. The surface normal is perturbed by the texture differential - the rate of its change in UV space.

------------------------------
Topic: How do bump maps work? (no, really) (4 of 8), Read 126 times
Conf: Rendering Materials & Lighting
From: Tim Chang
Date: Sunday, August 24, 2003 10:45 PM

>You may have found that
>certain black & white
>maps don't produce bumps
>at all. Try using any texture
>to mix between black &
>white in a Mix map,
>for example - absolutely
>no bump effect.

Yes. For along time I thought a bump channel was anything with b & w values that I could see in the material editor. All you did was stick it in the bump slot and there it was: a bump channel. The image generators in the ME (eg. bitmap maps, gradient ramp maps, noise maps) give that impression because they automatically create a corresponding bump channel that matches the RGB level of the image. I'll put my hand up and say I was easily fooled into thinking they were one and the same thing, and that the difference only came about because of the use that you put it to (either the diffuse slot or the bump slot). Now I know better.

TC

------------------------------
Topic: How do bump maps work? (no, really) (5 of 8), Read 123 times
Conf: Rendering Materials & Lighting
From: Ben Lipman
Date: Monday, August 25, 2003 07:06 AM

Maybe my resent experiences in codeland can offer some insight. A bump map is a method for perturbing a surfacenormal based on some texture. Usually this texture is the intensity of the map(mono channel, greyscale). The derivative (rate of change) of the U and V becomes normalperturb, usually. BUT. This only thing guaranteed about a bump map is that the normalperturb function of that map is called. That code can be anything. For instance, my gammamap plugin doesn't have any bump map code. It just calls for the normal perturb code of the submap. (It's a pass through.) My gNormal map plugin uses submap color information to perturb normals.

So what have we learned.
1. The normal perturbing code is within each texture, not the shader.
2. The texture directly sitting in the bumpmap slot gets called for the bump code.
3. This texture might not have any bumpping code. {return point3(0,0,0);}

hope this helps.

Ben.

------------------------------
Topic: How do bump maps work? (no, really) (6 of 8), Read 95 times
Conf: Rendering Materials & Lighting
From: Tim Chang
Date: Tuesday, August 26, 2003 12:52 AM

Thanks guys. I'm getting the picture.

Ben, your gNormal map-type would seem to be the plugin that was recommended to me. Will it work in max4?

I've downloaded a utility from ATI that contains a max model exporter and normal map generator, so I'll have a play with that. Since this is only for personal interest I can't justify purchase of Mankua's Kaldera (although it interests me greatly).

There's also a "Discreet Normalmap Generator Utility". Does anyone know if this is this freely available, and if so, where from? Does it do anything beyond the ATI utilities?

fooTools also has a Normal TExture map but I think it's only good for putting Normals into the Diffuse slot (to view), not the Bump slot.

TC

------------------------------
Topic: How do bump maps work? (no, really) (7 of 8), Read 103 times
Conf: Rendering Materials & Lighting
From: Ben Lipman blipman@anatomicaltravel.com
Date: Tuesday, August 26, 2003 06:45 AM

>Ben, your gNormal map-type
>would seem to be the plugin
>that was recommended to me.
>Will it work in max4?
>

no. sorry.

>I've downloaded a utility from
>ATI that contains a max model
>exporter and normal map
>generator, so I'll have a play
>with that. Since this is only
>for personal interest I can't
>justify purchase of Mankua's
>Kaldera (although it interests
>me greatly).
>
I haven't tryed Kaldara so I can't commnent.


>There's also a "Discreet
>Normalmap Generator Utility".
>Does anyone know if this is
>this freely available, and if
>so, where from?

it should be on discreet website. somewhere.

Does it do
>anything beyond the ATI
>utilities?
>

its easier to use. I hear. since ati is commandline.

>fooTools also has a Normal
>TExture map but I think it's
>only good for putting Normals
>into the Diffuse slot (to
>view), not the Bump slot.
>

John Burnett's normal texture is for generating rgb from normals.
you can use this with render-to-texture to make normalmaps.

I am only aware of kaldara and my plugin that will let you render normal maps in the max renderer.(not realtime dx9 stuff)

Ben.

------------------------------
Topic: How do bump maps work? (no, really) (8 of 8), Read 99 times
Conf: Rendering Materials & Lighting
From: Tim Chang
Date: Tuesday, August 26, 2003 06:35 PM

Ben, thanks. Mucho Gracias.

TC

[Stroker]

Dude. Big thanks for that.
Reminds me of something Teddy said: "It's not in the box. It's in the band."

(I really should start frequenting the Discreet forums.)

I'll have to do some more digging so I can understand the process completely, totally, and explicitly. Then I'll get to writing about it. In the meantime, I guess I'll stick to other MatEd tutorials. Once I get a few more done, I'll post a link in the resources sub-forum.

Again, thanks.

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