pass custom attribute defined in GeometryInstance to the vertex shader

[mickae1]

Feature

For the moment, it's not possible to put custom attribute defined in the GeometryInstance to the vertexShader, this would be great to add more flexibility.

const geometryInstance1 = new Cesium.GeometryInstance(
	{
		geometry: new Cesium.PolylineGeometry({
		  positions : Cesium.Cartesian3.fromDegreesArray([
			0.0, 0.0,
			5.0, 0.0,
			5.0, 5.0
		  ]),
		  width : 10.0,
		  arcType: Cesium.ArcType.GEODESIC
		}),
		attributes: {
                    test: new Cesium.GeometryInstanceAttribute({
                               componentDatatype : Cesium.ComponentDatatype.FLOAT,
                               componentsPerAttribute : 1,
                               normalize : true,
                               value : [50]
                           })
		}
	}
);
const geometryInstance2 = new Cesium.GeometryInstance(
	{
		geometry: new Cesium.PolylineGeometry({
		  positions : Cesium.Cartesian3.fromDegreesArray([
			0.0, 0.0,
			-5.0, 0.0,
			-5.0, -5.0
		  ]),
		  width : 10.0,
		  arcType: Cesium.ArcType.GEODESIC
		}),
		attributes: {
                    test: new Cesium.GeometryInstanceAttribute({
                               componentDatatype : Cesium.ComponentDatatype.FLOAT,
                               componentsPerAttribute : 1,
                               normalize : true,
                               value : [50]
                           })
		}
	}
);





const primitive = new Cesium.Primitive({
  geometryInstances : [geometryInstance1, geometryInstance2],
  appearance: new Cesium.PolylineMaterialAppearance({
	translucent: false,
	vertexShaderSource: vertexShader,
	fragmentShaderSource: fragmentShader,
	material: new Cesium.Material({
	  // https://github.com/CesiumGS/cesium/wiki/Fabric
	  fabric: {
		materials: {
		  // The arrowMaterial provides the color and overall shape.
		  arrowMaterial: {
			uniforms: {
                              genericVariable that can be catched by the fragment shader
                              ....