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 identical to textures for vanilla model JSON files. However, the textures are only available and applied only when JMX is loaded.

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": {
        "layer0": "cutout_mipped",
        "layer1": "cutout_mipped",
        "emissive1": true,
        "ambient_occlusion1": false,
        "diffuse1": false
    }
}

The material attributes that can be specified are listed below. The -N suffix must be 0 or 1 and indicates which sprite layer is affected. If an attribute is omitted, the default value will be used.

Attribute Name	Default Value	Description
layerN	solid	Render layer for this sprite. See Choosing the Right Layer(s) for more info.
emissiveN	false	When true, sprite texture and color will be rendered at full brightness.
ambient_occlusionN	determined by model	When true, sprite color will be modified for ambient occlusion shading.
diffuseN	determined by shade attribute	When true, sprite color will be modified for diffuse shading.
colorIndexN	true	When true, sprite color will be affected by the quad's color index. (If the color index is some value other than -1.)
colorN	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.
depth	2 if any other attribute references the second layer. 1 otherwise.	Only necessary when a double-layer material is needed but no attributes for the second layer are present. A value of 1 is ignored if any other attribute references the second layer.
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."

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 three 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_tex0": "#jmx_tex_down0", "jmx_tex1": "#jmx_tex_down1", "jmx_material": "#jmx_mat_down" },
                "up":    { "texture": "#up", "cullface": "up", "jmx_tex0": "#jmx_tex_up0", "jmx_tex1": "#jmx_tex_up1", "jmx_material": "#jmx_mat_up" },
                "north": { "texture": "#north", "cullface": "north", "jmx_tex0": "#jmx_tex_north0", "jmx_tex1": "#jmx_tex_north1", "jmx_material": "#jmx_mat_north" },
                "south": { "texture": "#south", "cullface": "south", "jmx_tex0": "#jmx_tex_south0", "jmx_tex1": "#jmx_tex_south1", "jmx_material": "#jmx_mat_south" },
                "west":  { "texture": "#west", "cullface": "west", "jmx_tex0": "#jmx_tex_west0", "jmx_tex1": "#jmx_tex_west1", "jmx_material": "#jmx_mat_west" },
                "east":  { "texture": "#east", "cullface": "east", "jmx_tex0": "#jmx_tex_east0", "jmx_tex1": "#jmx_tex_east1", "jmx_material": "#jmx_mat_east" }
            }
        }
    ]
}

The tags and their meaning are as follows.

Tag	Description
jmx_tex0	Reference to a texture variable defined in a textures element. Must be prefixed with a #. Will be used for the first sprite layer if present. If not present, the vanilla texture attribute will be used instead.
jmx_tex1	Reference to a texture variable defined in a textures element. Must be prefixed with a #. Will be used for the second sprite layer and must be present if the quad material has two sprite layers. If not present, the quad will have the "missing" texture. Set to null to quiet errors for missing textures when using parent JMX models that define both textures but only the first is needed.
jmx_uv_rot0 jmx_uv_rot1	Defines non-locked UV texture coordinates and/or texture rotation for the first or second 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 sprite defined by jmx_tex0 or jmx_tex1.
jmx_material	TODO