Reference: JMX Specification

NOTE: You should already be familiar with the un-modded Minecraft JSON model format before trying to create JMX model files. You can find more information on the Gamepedia Minecraft Wiki.

JMX Model Overrides

The jmx root-level tag defines textures and materials that should be used when JMX is loaded. It will not be used if a frex tag is present and a FREX renderer (i.e. Canvas) is active.

"jmx": {
    "textures": { },
    "materials": { }
}

FREX Model Overrides

The frex root-level tag defines textures and materials that should be used when a FREX renderer (i.e. Canvas) is active. When present and active, it overrides the jmx tag.

A frex block allows models to use different textures and material properties when shaders are available. Such models should still define a still-enhanced-but-without-shaders appearance in the jmx block to be used when shaders aren't available.

This "override" behavior only applies within the same JSON file. Texture and material names within the frex block can reference texture and material names provided via jmx blocks in other JSON model files (or even vanilla models for texture names.)

"frex": {
    "textures": { },
    "materials": { }
}

Textures

Textures are included in the jmx or frex elements via the textures tag. Usage of this tag is similar to textures for vanilla model JSON files. However, the textures are only available and applied only when JMX is loaded. Additionally, the special tag layered_textures can be used to apply textures to a certain sprite layer.

The layered_textures tag should contain an array of objects. Each object in the array has the same format as a regular textures object, but the textures defined within are adapted by JMX to match up with the given sprite layer.

If jmx and frex elements are both present, only one of them will be loaded. If a FREX-compliant renderer is active, the frex textures will be used. Otherwise the textures in the jmx element will apply.

Note that a vanilla textures element at the root level is not overriden by the jmx and frex blocks. This avoids compatibility problems with parent/child vanilla models that may still depend on the vanilla textures. For this reason, texture variable names within a block (names that are meant to be used with a # prefix) should be different from their vanilla counterparts.

Materials

Materials operate much like textures, but instead define a RenderMaterial to be associated with one or more faces.

Like textures, a materials element can occur inside both the jmx and frex elements. When a FREX renderer is active, the materials in the frex element will be used instead of the materials inside the jmx element.

A material value can be defined three ways:

Material Variable Reference

As with textures, materials can reference material variables to be defined in a child model, using the # prefix.

"materials": {
    "jmx_mat_down": "#jmx_mat_all",
    "jmx_mat_up": "#jmx_mat_all",
    "jmx_mat_north": "#jmx_mat_all",
    "jmx_mat_east": "#jmx_mat_all",
    "jmx_mat_south": "#jmx_mat_all",
    "jmx_mat_west": "#jmx_mat_all"
}

Material Properties

Material attributes can be directly specified within a sub-element. The name of the sub-element will be used to resolve symbolic material names.

"materials": {
    "jmx_mat_all": {
        "layers": [
            { "layer": "cutout_mipped" },
            { "layer": "cutout_mipped", "emissive": true, "ambient_occlusion": false, "diffuse": false }
        ]
    }
}

The material attributes that can be specified are listed below. If an attribute is omitted, the default value will be used.

Attribute Name	Default Value	Description
layers	(none)	List of material layer attribute objects.
depth	length of layers array, 0 if layers is not present.	Defines the number of sprite layers. Can be larger than the size of layers.
tag	0	Can be used to identify quads or carry other information. Useful when the quad is meant to transformed or filtered by a mod.
preset	(none)	See the following section on "Named Materials."

The material layer attributes that can be specified are listed below. If an attribute is omitted, the default value will be used.

Attribute Name	Default Value	Description
layer	solid	Render layer for this sprite. See Choosing the Right Layer(s) for more info.
emissive	false	When true, sprite texture and color will be rendered at full brightness.
ambient_occlusion	determined by model	When true, sprite color will be modified for ambient occlusion shading.
diffuse	determined by shade attribute	When true, sprite color will be modified for diffuse shading.
colorIndex	true	When true, sprite color will be affected by the quad's color index. (If the color index is some value other than -1.)
color	true	Values other than 0xFFFFFFFF modify the sprite color. The effect is in addition to any tinting done via quad color index. Colors must be in ARGB order and can be signed integers or hex values that begin with 0x.

Technical Note: In the Fabric Renderer API color and tag are not attributes of a render material but are instead part of the quad itself. JMX represents colors and tags as part of a material so they can be easily included in material inheritance.

Named Materials

"materials": {
    "jmx_mat_all": { "preset": "jmx:redstone" }
}

The preset tag causes JMX to look for a named render material that is pre-registered by the active renderer or by another mod.

If a named material is found, it will override all other material settings except color and tag.

Presets are useful for shader-based materials in the Canvas Render. FREX provides a material loader that can create named, custom shader materials without Java code. For more information, see: How To: Create Named Shader Materials with JSON Files

Face Element Extensions

JMX introduces new tags that can be included in a model face element.

{
    "parent": "minecraft:block/block",
    "elements": [
        {
            "from": [ 0, 0, 0 ],
            "to": [ 16, 16, 16 ],
            "faces": {
                "down": {
                    "texture": "#down",
                    "cullface": "down",
                    "jmx_material": "#jmx_mat_down",
                    "layered_textures": [ { "jmx_tex": "#jmx_tex_down" }, { "jmx_tex": "#jmx_tex_down" } ]
                },
                "up": {
                    "texture": "#up",
                    "cullface": "up",
                    "jmx_material": "#jmx_mat_up",
                    "layered_textures": [ { "jmx_tex": "#jmx_tex_up" }, { "jmx_tex": "#jmx_tex_up" } ]
                },
                "north": {
                    "texture": "#north",
                    "cullface": "north",
                    "jmx_material": "#jmx_mat_north",
                    "layered_textures": [ { "jmx_tex": "#jmx_tex_north" }, { "jmx_tex": "#jmx_tex_north" } ]
                },
                "south": {
                    "texture": "#south",
                    "cullface": "south",
                    "jmx_material": "#jmx_mat_south",
                    "layered_textures": [ { "jmx_tex": "#jmx_tex_south" }, { "jmx_tex": "#jmx_tex_south" } ]
                },
                "west": {
                    "texture": "#west",
                    "cullface": "west",
                    "jmx_material": "#jmx_mat_west",
                    "layered_textures": [ { "jmx_tex": "#jmx_tex_west" }, { "jmx_tex": "#jmx_tex_west" } ]
                },
                "east": {
                    "texture": "#east",
                    "cullface": "east",
                    "jmx_material": "#jmx_mat_east",
                    "layered_textures": [ { "jmx_tex": "#jmx_tex_east" }, { "jmx_tex": "#jmx_tex_east" } ]
                }
            }
        }
    ]
}

The tags and their meaning are as follows.

Tag	Description
layered_textures	An array of JMX texture data objects. If not present, the vanilla texture attribute will be used instead.
jmx_material	Reference to a material variable defined in a materials element. Must be prefixed with a #.

The JMX texture data format is defined below.

Tag	Description
jmx_tex	Reference to a texture variable defined in a textures element. Must be prefixed with a #.
jmx_uv_rot	Defines non-locked UV texture coordinates and/or texture rotation for the current sprite layer. Value must be an new element, enclosed by curly braces ( { } ), that contains a uv array, a rotation value, or both. The uv and rotation tags work the same as they normally do within a vanilla face element, except they apply only to the current sprite layer.