Hedgehog engine 1¶
Texture types¶
Hedgehog Engine 1 games limit themselves to a few texture types (with exceptions), which can make configuring materials difficult, as many shaders use certain types differently than what their name suggests.
Here is a list of all texture types and how they are most commonly used:
File formats and encodings¶
Textures are always stored in DDS files, of which the vast majority use some form of block-compression encoding. Only a handful are not compressed.
Since HE1 is programmed with Direct3D 9, the number of available block compression encodings is limited to BC1, BC2 and BC3.
More info on DDS block compression can be found here.
Note
The Direct3D 11 mod for Sonic Generations (PC) by Skyth makes the game run on Direct3D 11, which can read newer DDS encodings like BC4, BC5, BC6, BC7 and more.
Kinds of textures¶
The majority of textures used by materials are one of the following kind of textures.
Diffuse¶
Reference
- File suffix:
_dif
- Composition:
RGBA
- Recommended encoding:
BC1_UNORM
when opaqueBC3_UNORM
when transparent
Diffuse textures are color-transparency textures that are sampled directly for the base color of a material.
Opacity¶
Reference
- File suffix:
_alp
,_a
, Often none- Composition:
Grayscale
- Recommended encoding:
BC1_UNORM
Opacity textures determine the transparency of a material.
Usually transparency is relayed to Diffuse textures, and actual opacity textures are only used when special alpha compositing happens.
Falloff¶
Reference
- File suffix:
_fal
- Composition:
Color
- Recommended encoding:
BC1_UNORM
Falloff textures change the color of the diffuse texture based on the viewing angle: The greater the angle between the camera and the surface of the model, the greater the influence.
Depending on the shader, the falloff color either gets mixed with the diffuse color or added to it.
Additionally, shaders with falloff colors or textures basically always come with a parameter that controls how the falloff factor gets calculated.
Environment map¶
Reference
- File suffix:
_ref
,_env
,_cube
- Composition:
RGBA
- Recommended encoding:
BC1_UNORM
when opaque,BC3_UNORM
when transparent
Environment textures are used to project a fake reflection of the surroundings onto a model based on the viewing angle.
Some get layered on top of e.g. a diffuse texture, and have an alpha channel for their layer-transparency.
Depending on the shader, these have 3 different layouts:
Cubemap¶
The most detailed, and probably best known type of reflection map. Uses 6 square areas, one for each side of a cube, to represent reflections from each axis.
Spherical environment map¶
The cheapest type of reflection, which always directly faces the camera.
Also known as MatCap textures.
Dual paraboloid environment map¶
Effectively a full skybox composed of 2 spherical environment maps that cover the front and back of an environment.
Covers the same area as a cubemap but with less detail.
Emission¶
Reference
- File suffix:
_ems
,_lum
- Composition:
Color
- Recommended encoding:
BC1_UNORM
Emission textures make parts of a model emit light.
Specular¶
Reference
- File suffix:
_spc
- Composition:
RGBA
- Recommended encoding:
BC3_UNORM
Specular textures contain 2 different maps:
The blinn phong lighting specular color in the RGB channels
The environment map (reflection) influence in the alpha channel
Gloss¶
Reference
- File suffix:
_pow
- Composition:
Grayscale
- Recommended encoding:
BC1_UNORM
Gloss textures determine the blinn phong lighting specular power.
Note
Almost every Hedgehog Engine 1 game calculates the gloss factor differently, which may cause the same gloss texture to look different in each game.
Normal map¶
Reference
- File suffix:
_nrm
(rarely_norm
,_nor
,_nml
)- Composition:
Color
- Recommended encoding:
BC1_UNORM
Normal map textures are used for faking bumps and dents on a model to affect lighting, falloff, environment maps and similar.
Note
Compared to blender, the green channel is inverted. This gets adjusted on import/export.