Bump map

A material's albedo (left) compared to its bump map.

The above material in-game.

Textures often called Bump Maps, or Normal Maps are used to simulate three-dimensional details on a two-dimensional surface by manipulating its lighting.

Note:Static props using bump maps can not be lit per-vertex, except in

. $lightmap is also incompatible with $bumpmap.

Note:Bump maps cannot be used on decal textures, except in

. In order for these to function properly, the surface that they are placed on must also have a bumpmap.

Format

Each pixel in a bump map contains the (x, y, z) coordinates that define a normalized vector.

Because of this each color channel in a bump map has a meaning:

Red

Horizontal facing (X axis)

0 = left
128 = forward, or facing viewer
255 = right

Green

Vertical facing (Y axis)

0 = up
128 = forward, or facing viewer
255 = down

Blue

Height (Z axis).

0 = facing 'in' to the texture, away from the viewer. This is a 'bad' value. Anything under 128 means that the surface should be facing away from the player, which is not possible.
128 = maximum depth capable of receiving dynamic light. It's a bad idea to go under this.
255 = facing 'out' of the texture towards the viewer.

Note:A flat bump map should be [128, 128, 255]. dev/flat_normal is a flat bump map present in every game.

The three channels represent a normal vector for every pixel which represents the direction that the pixel is facing in 3D space. This allows the engine to generate shadows and highlights on a two-dimensional surface, or give a 3D model more detail.

A bump map is largely useless for really flat surfaces like smooth concrete or metal, but even smooth concrete sometimes has enough depth to it to make one worthwhile, especially if used in conjunction with a cubemap.

Creation

A bump map should be rendered in Tangent space and use vector directions X+ Y- Z+.

Note:There are basically two sets of rules for normal maps: DirectX and OpenGL. Their interpretation of green channels are opposite. Source takes the former, whereas Source 2 takes the latter. Thus, the green channel may need to be inverted depending on the software used to create it.

Programs

Bump maps as created by various programs.

Various programs can automate the creation of bump maps, either by image analysis or by using 3D geometry the user provides.

2D: Photoshop or Paint Shop Pro; Substance Designer; The GIMP; nDo; Filter Forge; XBLAH's Modding Tool; nJob
3D: XSI; ZBrush; Lightwave; 3ds Max; Maya; Blender; Materialize; NVIDIA Melody; Cinema 4D; NormalMapper; xNormal
Other: NormalMap Online: A website for generating normal maps online.; SSBump Generator 5.3: Despite the name, it can also be used to generate bumpmaps, not just self-shadowing bump maps.; Substance B2M3: Previously known as BitMap2Material.; InsaneBump: Specifically made to be a free alternative to the now-superseded software "CrazyBump" (may trip antiviruses due to incompatibility)

Conversion

In VTFEdit

When converting your texture:

Choose your image format. Uncompressed formats like BGR888 are higher-quality than compressed formats like DXT1, but be wary of file size.
Check the "Normal map" box in the texture's flags list after the import is complete. It's about 1/5 of the way down the list.

Tip:VTFEdit can automatically generate bump maps. See the bottom-right of the import screen.

In Vtex

Save your normal map as a TGA. Give it a name that ends in _normal. The _normal at the end of the name will affect how Vtex converts it. For the brick wall example, we would name the file brickwall_normal.tga.
Add nocompress 1 and normal 1 to <texture filename>.txt in the same folder as your texture, then compile.

Implementation

Normal maps can be generated from a basetexture, using the Sobel Operator, by sampling the HSB Brightness of each pixel and adjoining pixel to determine the scale of the output Hue and Saturation values that are subsequently converted to RGB for the SetPixel operation.

   Bitmap image = (Bitmap) Bitmap.FromFile(@"yourpath/yourimage.jpg");
   int w = image.Width - 1;
   int h = image.Height - 1;
   float sample_l;
   float sample_r;
   float sample_u;
   float sample_d;
   float x_vector;
   float y_vector;
   Bitmap normal = new Bitmap(image.Width, image.Height);
   for (int y = 0; y < w + 1; y++)
   {
       for (int x = 0; x < h + 1; x++)
       {
           if (x > 0) { sample_l = image.GetPixel(x - 1, y).GetBrightness(); }
           else { sample_l = image.GetPixel(x, y).GetBrightness(); }
           if (x < w) { sample_r = image.GetPixel(x + 1, y).GetBrightness(); }
           else { sample_r = image.GetPixel(x, y).GetBrightness(); }
           if (y > 1) { sample_u = image.GetPixel(x, y - 1).GetBrightness(); }
           else { sample_u = image.GetPixel(x, y).GetBrightness(); }
           if (y < h) { sample_d = image.GetPixel(x, y + 1).GetBrightness(); }
           else { sample_d = image.GetPixel(x, y).GetBrightness(); }
           x_vector = (((sample_l - sample_r) + 1) * .5f) * 255;
           y_vector = (((sample_u - sample_d) + 1) * .5f) * 255;
           Color col = Color.FromArgb(255, (int)x_vector, (int)y_vector, 255);
           normal.SetPixel(x, y, col);
       }
   }

See $bumpmap.

Bump map

Contents

Format