Add joint control to gltf model

GLTF Add joint control to the model

1. Preface

stay Cesium The official example provides an example of controlling the separation of the rocket fairing , Example link CZML Model Articulations. This example shows how to control glb/gltf In the model articulations To control the movement of some joints of the model . The premise is that There are in the model file articulations attribute , This article mainly introduces how to do it in Blender And other 3D modeling software gltf Add... To the model articulations attribute .

2. Environmental preparation

• Blender Or other mainstream 3d modeling software ： Used to export gltf Model
• VS Code： Need to install plug-ins glTF Tools and STK GMDF Tools, for gltf Model preview and injection articulations attribute
• Three dimensional model ： You can go to https://github.com/AnalyticalGraphicsInc/gmdf/tree/master/samples download

3. Operation steps

1. Blender Open the 3D model , With samples\VehicleTest\source\VehicleTest.blend For example , It can be seen that the model mainly includes the body 、 Front wheel and rear wheel , Exporting gltf After that can be nodes Find the corresponding part under the attribute ;

   

2. export gltf Format model ;

   

3. VS Code Preview gltf Model , You can see gltf In the document nodes Including the front wheels mentioned above 、 The rear wheel , Next, you can control the movement of the front and rear wheels by adding attributes ;

   

4. stay VehicleTest.gltf Created in the same level directory VehicleTest.gmdf file , The contents of the document are as follows ：

{
    
    "AGI_articulations": {
    
        "articulations": [
            {
    
                "name": "Wheels",
                "stages": [
                    {
    
                        "name": "Drive",
                        "type": "xRotate",
                        "minimumValue": -360,
                        "maximumValue": 360,
                        "initialValue": 0
                    }
                ],
                "modelNodes": [
                    "FrontWheels",
                    "RearWheels"
                ]
            }
        ]
    }
}

AGI_articulations and articulations All in fixed format , Main concern modelNodes and stages.modelNodes Used to describe the model joints to be controlled , It is the front and rear wheels in the above ;stages Used to explain how joints move , In the example type Indicates that the joint type is along x Shaft rotation ,minimumValue and maximumValue Used to control the range . For more specific meanings of attribute fields, please refer to https://github.com/KhronosGroup/glTF/blob/main/extensions/2.0/Vendor/AGI_articulations/README.md#overview

5. take gmdf File injection into gltf file , First, in the VS Code Choose VehicleTest.gltf file , Press and hold the shortcut key Ctrl + Shift + P, Search for GMDF, Choose the command inject GMDF into glTF, Then you can see in gltf There are new contents added in the document , After saving, you can see the operation interface of controlling joint motion in the model preview interface , You can control the movement of the wheel by dragging the slider ;

   

   

   

4. Reference link

[1]. Cesium Example

[2]. GMDF Tools and glTF Model example

[3]. AGI_articulations Detailed introduction

[4]. Converting Models To GlTF For STK