# Saving and Loading Materials with .j3m Files

In the Material Definitions article you learned how to configure Materials programmatically in Java code. If you have certain commonly used Materials that never change, you can clean up the amount of Java code that clutters your init method, by moving material settings into .j3m files. Then later in your code, you only need to call one setter instead of several to apply the material.

If you want to colorize simple shapes (one texture all around), then .j3m are the most easily customizable solution. J3m files can contain texture mapped materials, but as usual you have to create the textures in an external editor, especially if you use UV-mapped textures.

## Writing the .j3m File

1. For every Material, create a file and give it a name that describes it: e.g. `SimpleBump.j3m`
2. Place the file in your project's `assets/Materials/` directory, e.g. `MyGame/src/assets/Materials/SimpleBump.j3m`
3. Edit the file and add content using the following Syntax, e.g.:

       Material shiny bumpy rock : Common/MatDefs/Light/Lighting.j3md {
            MaterialParameters {
                Shininess: 8.0
                NormalMap: Textures/bump_rock_normal.png
                UseMaterialColors : true
                Ambient  : 0.0 0.0 0.0 1.0
                Diffuse  : 1.0 1.0 1.0 1.0
                Specular : 0.0 0.0 0.0 1.0
            }
       }

How to this file is structured:

1. Header
   1. `Material` is a fixed keyword, keep it.
   2. `shiny bumpy rock` is a descriptive string that you can make up. Choose a name to help you remember for what you intend to use this material.
   3. After the colon, specify on which Material definition you base this Material.
2. Now look up the choosen Material Definition's parameters and their parameter types from the Material table. Add one line for each parameter.
   - For example: The series of four numbers in the example above represent RGBA color values.
3. Check the detailed syntax reference below if you are unsure.

In the jMonkeyEngine SDK, use File→New File→Material→Empty Material File to create .j3m files. You can edit .j3m files directly in the SDK. On the other hand, they are plain text files, so you can also create them in any plain text editor.

## How to Use .j3m Materials

This is how you use the prepared .j3m Material on a Spatial. Since you have saved the .j3m file to your project's Assets directory, the .j3m path is relative to `MyGame/src/assets/…`.

    myGeometry.setMaterial(assetManager.loadMaterial("Materials/SimpleBump.j3m"));

Tip: In the jMonkeyEngine SDK, open Windows>Palette and drag the `JME Material: Set J3M` snippet into your code.

## Syntax Reference for .j3m Files

### Paths

Make sure to get the paths to the textures (.png, .jpg) and material definitions (.j3md) right.

- The paths to the built-in .j3md files are relative to jME3's Core Data directory. Just copy the path stated in the Material table.
  `Common/MatDefs/Misc/Unshaded.j3md` is resolved to `jme3/src/src/core-data/Common/MatDefs/Misc/Unshaded.j3md`.
- The paths to your textures are relative to your project's assets directory.
  `Textures/bump_rock_normal.png` is resolved to `MyGame/src/assets/Textures/bump_rock_normal.png`

### Data Types

All data types (except Color) are specified in com.jme3.shader.VarType. “Color” is specified as Vector4 in J3MLoader.java.

Name | jME Java class | .j3m file syntax
--- | --- | ---
Float | (basic Java type) | a float (e.g. 0.72) , no comma or parentheses
Vector2 | `com.jme3.math.Vector2f` | Two floats, no comma or parentheses
Vector3 | `com.jme3.math.Vector3f` | Three floats, no comma or parentheses
Vector4 | `com.jme3.math.Vector4f` | Four floats, no comma or parentheses
Texture2D | `com.jme3.texture.Texture2D` | Path to texture in `assets` directory, no quotation marks
Texture3D | `com.jme3.texture.Texture3D` | Same as texture 2D except it is interpreted as a 3D texture
TextureCubeMap | `com.jme3.texture.TextureCubeMap` | Same as texture 2D except it is interpreted as a cubemap texture
Boolean | (basic Java type) | `true` or `false`
Int | (basic Java type) | Integer number, no comma or parentheses
Color | `com.jme3.math.ColorRGBA` | Four floats, no comma or parentheses
FloatArray |  | (Currently not supported in J3M)
Vector2Array |  | (Currently not supported in J3M)
Vector3Array |  | (Currently not supported in J3M)
Vector4Array |  | (Currently not supported in J3M)
Matrix3 |  | (Currently not supported in J3M)
Matrix4 |  | (Currently not supported in J3M)
Matrix3Array |  | (Currently not supported in J3M)
Matrix4Array |  | (Currently not supported in J3M)
TextureBuffer |  | (Currently not supported in J3M)
TextureArray |  | (Currently not supported in J3M)

### Flip and Repeat Syntax

- A texture can be flipped using the following syntax `NormalMap: Flip Textures/bump_rock_normal.png`
- A texture can be set to repeat using the following syntax `NormalMap: Repeat Textures/bump_rock_normal.png`
- If a texture is set to both being flipped and repeated, Flip must come before Repeat

### Syntax for Additional Render States

- A Boolean can be “On” or “Off”
- Float is “123.0” etc
- Enum - values depend on the enum

See the
javadoc for a detailed explanation of render states.

Name | Type | Purpose
--- | --- | ---
| (Boolean) | Enable wireframe rendering mode
| (Enum: FaceCullMode) | Set face culling mode (Off, Front, Back, FrontAndBack)
| (Boolean) | Enable writing depth to the depth buffer
| (Boolean) | Enable depth testing
| (Enum: BlendMode) | Set the blending mode
| (Float) | Set the alpha testing alpha falloff value (if set, it will enable alpha testing)
| (Float, Float) | Set the polygon offset factor and units
| (Boolean) | Enable color writing
| (Boolean) | Enable point sprite rendering for point meshes

## Examples

### Example 1: Shiny

    Spatial signpost = (Spatial) assetManager.loadAsset(
        new OgreMeshKey("Models/Sign Post/Sign Post.mesh.xml", null));
    signpost.setMaterial( assetManager.loadMaterial(
        new AssetKey("Models/Sign Post/Sign Post.j3m")));
    TangentBinormalGenerator.generate(signpost);
    rootNode.attachChild(signpost);

The file `assets/Models/Sign Post/Sign Post.j3m` contains:

    Material Signpost : Common/MatDefs/Light/Lighting.j3md {
        MaterialParameters {
             Shininess: 4.0
             DiffuseMap:  Models/Sign Post/Sign Post.jpg
             NormalMap:   Models/Sign Post/Sign Post_normal.jpg
             SpecularMap: Models/Sign Post/Sign Post_specular.jpg
             UseMaterialColors : true
             Ambient  : 0.5 0.5 0.5 1.0
             Diffuse  : 1.0 1.0 1.0 1.0
             Specular : 1.0 1.0 1.0 1.0
        }
    }

The JPG files are in the same directory, `assets/Models/Sign Post/…`.

### Example 2: Repeating Texture

    Material mat = assetManager.loadMaterial(
        "Textures/Terrain/Pond/Pond.j3m");
    mat.setColor("Ambient", ColorRGBA.DarkGray);
    mat.setColor("Diffuse", ColorRGBA.White);
    mat.setBoolean("UseMaterialColors", true);

The file `assets/Textures/Terrain/Pond/Pond.j3m` contains:

    Material Pong Rock : Common/MatDefs/Light/Lighting.j3md {
         MaterialParameters {
             Shininess: 8.0
             DiffuseMap: Repeat Textures/Terrain/Pond/Pond.png
             NormalMap:  Repeat Textures/Terrain/Pond/Pond_normal.png
         }
    }

The PNG files are in the same directory, `assets/Textures/Terrain/Pond/`

### Example 3: Transparent

The file `assets/Models/Tree/Leaves.j3m` contains:

    Material Leaves : Common/MatDefs/Light/Lighting.j3md {

        Transparent On

        MaterialParameters {
            DiffuseMap : Models/Tree/Leaves.png
            UseAlpha : true
            AlphaDiscardThreshold : 0.5
            UseMaterialColors : true
            Ambient : .5 .5 .5 .5
            Diffuse : 0.7 0.7 0.7 1
            Specular : 0 0 0 1
            Shininess : 16
        }
        AdditionalRenderState {
            Blend Alpha
            AlphaTestFalloff 0.50
            FaceCull Off
        }
    }

The PNG file is in the same directory, `assets/Models/Tree/…`

## Related Links

- Developer specification of the jME3 material system (.j3md,.j3m)

tag_material_texture_file_sdk_wireframe_documentation

view online version