Hedgehog Engine - Textures
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:
| Type | Primarily used with | Occasionally used with |
|---|---|---|
| diffuse | Diffuse | Emission |
| opacity | Opacity | Diffuse |
| reflection | Environment Map | / |
| specular | Specular | Diffuse, Gloss |
| gloss | Gloss | Diffuse, Specular |
| normal | Normal map | / |
| displacement | General use texture type | Falloff, Emission |
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.
Kinds of textures
The majority of textures used by materials are one of the following kind of textures.
Diffuse
| Texture overview | |
|---|---|
| File Suffix | _dif
|
| Composition | RGBA
|
| Recommended encoding |
|
Diffuse textures are color-transparency textures that are sampled directly for the base color of a material.
Opacity
| Texture overview | |
|---|---|
| File Suffix | _alp, _a, often none at all
|
| Composition | Grayscale
|
| Recommended encoding |
|
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
| Texture overview | |
|---|---|
| File Suffix | _fal
|
| Composition | Color
|
| Recommended encoding |
|
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
| Texture overview | |
|---|---|
| File Suffix | _ref, _env, _cube
|
| Composition | RGBA
|
| Recommended encoding |
|
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
| Texture overview | |
|---|---|
| File Suffix | _ems, _lum
|
| Composition | Color
|
| Recommended encoding |
|
Emission textures make parts of a model emit light.
Specular
| Texture overview | |
|---|---|
| File Suffix | _spc
|
| Composition | RGBA
|
| Recommended encoding |
|
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
| Texture overview | |
|---|---|
| File Suffix | _pow
|
| Composition | Grayscale
|
| Recommended encoding |
|
Gloss textures determine the blinn phong lighting specular power.
Normal Map
| Texture overview | |
|---|---|
| File Suffix | _nrm (rarely _norm, _nor, _nml)
|
| Composition | Color
|
| Recommended encoding |
|
Normal map textures are used for faking bumps and dents on a model to affect lighting, falloff, environment maps and similar.
See normal mapping for reference.