What's a bump map?

I know it sounds stupid, but what is it? :confused:

Bump maps (and Normal maps)

One could say that bumpmaps affect how bright which parts of the underlying texture will be in the final output, right?

No, those are Reflection maps, or Diffuse maps.

They are short cuts to lighten the load on weary Blender artists. :wink:

They come in two types: Normal maps and Displacement maps.

Now, if you were making a Blender mesh of a spaceship that had lots of hull plate edge lines all over it, you could cut every single line into the mesh. It would look real nice, but it would take you weeks to do. So instead one can use Normal maps or Displacement maps.

Both use a special type of texture map, one that is all gray scale. The whiter the section of the texture map, the “higher” the surface will be “bumped up.”

Now, with a Normal map, the surface of the mesh is not actually moved. Instead, fake highlights and shadows are painted on the rendered image to make the illusion of a bumpy surface. If you aim the camera edge on the surface the render will show that the surface is still flat.

With a Displacement map, the vertices are actually moved as per the texture map. But this means that the mesh has to have lots of vertices (generally done by doing a few levels of SubSurf) or the mesh will look like a tangled mess. This sends the polygon count through the roof.

So one uses Displacement maps when one doesn’t mind a large polygon count, otherwise use a Normal map.

Here is an example of a bump map. A sphere was subsurfed about four times, and the bump map shown was applied. The bump map was only 256x256 pixels. In the texture panel I hit the Disp button twice so it was yellow. This made it so the darker the map the more it was bumped up.
http://img159.imageshack.us/img159/3218/displacementmapoe1.th.jpg

So it’s like UV mapping, but easier? And you can get these off the net? How do you apply the map to an object?

Well, it is not really UV mapping. UV mapping is just a way to place materials on an object. It tells the object about the material orientation.

Some definitions (and perhaps a non-technical aproach to describe it), to help you in the djungle of different maps. Say you have an engraved golden watch and want to represent it in blender. In the real world you see it as one material: gold. To define “gold” in the computer we need to break it into different properties in order to accurately represent it. For example: we have the color (yellow), we store that property into something we call a colormap (also called diffuse map), we have the reflection - since it is a metal, we store that in a reflection map. Gold has shiny properties when light reflects on it, we call this specularity and hence stores it in a specular map. All these properties gives the watch it’s golden looks. If you took away the reflection for example it would not look like gold anymore but rather like plastic. If we instead took away the colormap it would be colorless and look like chrome, and so fourth. Now, bump mapping isn’t a conventional property like those I mentioned earlier. It’s sole purpose is to add “bumps” to the surface. Small features and imperfections, dents, engravings and so fourth. Stuff that really are 3D but generally are so small or complex that we would rather not represent them using polygons. Think for example if you had to model by hand every small rock in a gravel road. That would take ages. But still, you don’t want it to look like a flat picture. You want more realism, breathe some life into it. This is where bumpmaps come in handy. They make the gravel road look uneven and bumpy instead of flat. Bump maps are not 3D but gives the illusion of being so. What they do is really to reflect the light into different directions (instead of miroring it directly at you, like a flat surface would). This scattering of light fools your brin into seeing it like a 3D surface. It is a bit of a cheap effect sometimes and large details will look fake at close range. But smaller details like scratches, jewelry engravings (from a distance) and perhaps wrinkles on a face will gain a lot from the details added by a bump map. Normap maps are basicly the same thing but a bit more refined method. Displacement maps also tries to do the same thing but here the difference is that they DO actually change the 3D of the object. These are real 3D displacements and therefore gives the best result, but they require a very dense geometry on the object they are applied on to give a smooth and nice result. Bump and normalmaps does not.

Here is an example about the difference:
http://www.dm.univaq.it/blender236/PartM/textures/gfx/displacementMap_dispDiff.png

The image on the left is bump mapped. Without the bumpmap it would just be a smooth half-sphere. Now it looks like it has a rough surface, it is still smooth though. On the right is a displaced object. It is the same object as the left one, but with a displacement map instead. Just like the left object it has a rough surface, but instead of being a perfect half-sphere it has a lot of bumps and imperfections. This is because it’s geometry has been “displaced”. Parts of it’s surface have moved outward from the object. This gives a much more realistic impression of being a rough object.

Great info here guys. This cleared things up.thanx

Well, but a bumpmap does affect the direction of the surface normals, right? And that will result in different shading -> bumps.

I’ve never heard of reflection or diffuse maps. They’re not real textures, are they? Or do you mean environment mapping with reflection mapping? But that’s more like a property than a map, isn’t it?

Diffuse is obviously color, reflection map is another texture channel that can be used to set the reflection value, white parts of a greyscale image would be reflective while black parts non-reflective, this channel is the amount of light reflected off the material, not actual mirror reflections, you use the RayMir channel to affect that.

Specular would be similar to reflection except that it is the highlite, you could use it for example on the texture for a table top that is old and has worn spots that would not be shiny.

Here is an example of RayMir, Reflection, and Specular maps, plust the three images I used in the respective channels.

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uh ok thnx, but again, can i get some off the net?

You will have to register (it’s free) but there are some here:
http://www.lwg3d.org/v3/presets.php?cat=38

The Magma SFTP textures are in sets. So in the “Panels” archive, there is a Panel 5 Color texture, a Panel 5 Bump texture, a Panel 5 Diffuse Shading texture, and a Panel 5 Specularity texture.

Hazard, diffuse is not the color, that is not correct.

Diffuse is the amount of light which gets reflected by the body, or in other words how much bright or dark you can illuminate an object.

the amount of reflected light will let you see the object to be bright, or dark together with the objects own color.

specular are for example actualy not just the hightlight light illuminating but a reflection of the light emiting object. Thats also an issue in 3D apps. Light objects far away normaly produce a small specular and a light bulb very close creates a bigger specular reflection. That you have to set in Blender by hand. That is because the specular highlight is a real reflection.

The diffuse value is in relationship with the objects surface property.

actualy diffuse and specular cancel out the mirrow reflection because a perfect smooth surface would be reflective on its own.

this is all a bit abstract but makes much sense after understanding the light shader models. i can only advice to read the new second edition of:
Digital Lighting & Rendering

that book has some very good explanations about it.

http://www.amazon.com/gp/product/0321316312/sr=8-1/qid=1154297793/ref=pd_bbs_1/104-9884015-3882334?ie=UTF8

Ok, thank you…if anyone else has bump map sites, stick 'em here…

how do i open the files/use them??? (from the site)

You need to be registered and logged
in to be able to download the files.

i’ve alredy downloaded them, how do i put them into blender??

create a material, add a texture and for that texture select image.
and than just load the bumb map!

:wink:

In my experience with 3D (not too much) prior to Blender you found color in the diffuse channel, easily confused since without the light you would have no color, I should have stated that ‘Ref’ in Blender = Diffuse, since it is the amount of light coming from the surface, thanks for pointing that out, with different apps using different terms for the same thing, it can get confusing.

Hi Hazard,

no problem, that topic is just quite crazy. when you see it this way an object has also no reflective value. or let me say an object is always reflective but the vivibility of the reflection depends on the smoothness of the surface.

color is always linked to diffuse which makes sense but thats as far as i understand not quite right because diffuse deals with the absorbtion and reflection of the incoming light rays. the body color itself than provides the color. ah well anyway that is like we are counting peas :wink: