Bump map: Difference between revisions
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== Format == | == Format == | ||
Each | Each pixel in a bump map contains the (x, y, z) coordinates that define a normalized vector. (ex. A line with a length 1 unit centered at (0,0,0) that passes through the point (x,y,z) ) | ||
# The '''red''' channel defines horizontal facing (X-axis) | Because of this each color channel in a bump map has a meaning: | ||
# The '''red''' channel defines the horizontal facing (X-axis coordinate) of the vector | |||
#:0 = left | #:0 = left | ||
#:128 = forward (facing viewer) | #:128 = forward (facing viewer) | ||
#:255 = right | #:255 = right | ||
# The '''green''' channel defines vertical facing (Y-axis) | # The '''green''' channel defines the vertical facing (Y-axis coordinate) of the vector | ||
#:0 = up | #:0 = up | ||
#:128 = forward (facing viewer) | #:128 = forward (facing viewer) | ||
#:255 = down | #:255 = down | ||
# The '''blue''' channel defines height (Z-axis) | # The '''blue''' channel defines the height (Z-axis coordinate) of the vector | ||
#:0 = | #: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. This is not possible.) | ||
#:128 = maximum depth capable of receiving dynamic light (it's a bad idea to go under this) | #:128 = maximum depth capable of receiving dynamic light (it's a bad idea to go under this) | ||
#:255 = | #:255 = facing 'out' of the texture towards the viewer | ||
The three channels | The three channels represent a normal vector for every pixel, allowing the engine to generate shadows and highlights on a two-dimensional surface. This is usually done with a simple lighting calculation such as dot( N, L ) where 'dot' is the [http://en.wikipedia.org/wiki/Dot_product dot product] equation, 'N' is the normal vector stored in the pixel, and 'L' is the lighting vector (ex. The direction the light is facing). | ||
A bump map is largely useless for really flat surfaces like smooth concrete or metal, but even rough concrete sometimes has enough depth to it to make one worthwhile. | A bump map is largely useless for really flat surfaces like smooth concrete or metal, but even rough concrete sometimes has enough depth to it to make one worthwhile. | ||
Revision as of 18:42, 4 July 2009
A bump map is an RGB image that can be used to simulate a three-dimensional surface through a process known as normal mapping. They are sometimes called normal maps.
Format
Each pixel in a bump map contains the (x, y, z) coordinates that define a normalized vector. (ex. A line with a length 1 unit centered at (0,0,0) that passes through the point (x,y,z) )
Because of this each color channel in a bump map has a meaning:
- The red channel defines the horizontal facing (X-axis coordinate) of the vector
- 0 = left
- 128 = forward (facing viewer)
- 255 = right
- The green channel defines the vertical facing (Y-axis coordinate) of the vector
- 0 = up
- 128 = forward (facing viewer)
- 255 = down
- The blue channel defines the height (Z-axis coordinate) of the vector
- 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. This 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
The three channels represent a normal vector for every pixel, allowing the engine to generate shadows and highlights on a two-dimensional surface. This is usually done with a simple lighting calculation such as dot( N, L ) where 'dot' is the dot product equation, 'N' is the normal vector stored in the pixel, and 'L' is the lighting vector (ex. The direction the light is facing).
A bump map is largely useless for really flat surfaces like smooth concrete or metal, but even rough concrete sometimes has enough depth to it to make one worthwhile.
Creation
A bump map should:
- Be at the same resolution as the albedo/s it is to be used with.
- Be stored in an uncompressed format (see Conversion).
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
- The GIMP
- 3D
- XSI
- ZBrush2
- Lightwave
- 3D Studio Max
- Maya
- Blender
- NVIDIA Melody
- Cinema 4D
- NormalMapper
- xNormal
- Other
- CrazyBump: Produces some very good normal maps. Some of them can be argued as almost having the same depth as a parallax map.
- ShaderMap: A free alternative to CrazyBump.
- SSBump Generator 5.0: Another free alternative to CrazyBump that generates Self Shadowed Bump Maps as well as normal maps.
- Normal2dudv: a third party tool for converting bump maps to Dx8-friendly du/dv maps.
Conversion
In VTFEdit
When converting your texture:
- Choose BGR8888 or BGRA8888 (if your texture has an alpha channel) as your image format.
Tip:You can sometimes get away with DXT compression. - 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 in the same resolution as the original texture. 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 1andnormal 1to <texture filename>.txt in the same folder as your texture, then compile.
Implementation
See $bumpmap.
See also
$ssbump: creation and usage of Valve's new self-shadowing bump maps.- An old article that explains normal mapping quite well.
- Material Creation
- [1]
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