Draw Triangle - how?

CesiumJS
1

I am trying to draw a triangle and rotate with an snglle. I use React, cesium, resium with javascript.
I tries to use chatgpt to find a way but always get an error (tried Primitive etc)
Do you have a simple code that you know that works with which I czn use to draw triangle?

Thanks

2

Here’s Sample code

const {
	BoundingSphere,
	Cartesian3,
	Color,
	ColorGeometryInstanceAttribute,
	ComponentDatatype,
	GeometryAttribute,
	GeometryInstance,
	PerInstanceColorAppearance,
	Primitive,
	PrimitiveType,
	Viewer
} = window.Cesium;

const viewer = new Viewer("cesiumContainer", {});

const firstVertex = Cartesian3.fromDegrees(-115.0, 37.0);
const secondVertex = Cartesian3.fromDegrees(-115.0, 32.0);
const thirdVertex = Cartesian3.fromDegrees(-107.0, 33.0);

const positions = [firstVertex, secondVertex, thirdVertex];

const rawPositions = [
	firstVertex.x,
	firstVertex.y,
	firstVertex.z,
	secondVertex.x,
	secondVertex.y,
	secondVertex.z,
	thirdVertex.x,
	thirdVertex.y,
	thirdVertex.z
];

const index = [0, 1, 2];

const position = new GeometryAttribute({
	componentDatatype: ComponentDatatype.DOUBLE,
	componentsPerAttribute: 3,
	values: new Float64Array(rawPositions)
});

const trianglePrimitive = new Primitive({
	geometryInstances: new GeometryInstance({
		geometry: new Cesium.Geometry({
			attributes: {
				position: position
				// normal: normal,
				// st: st
			},
			indices: new Uint16Array(index),
			primitiveType: PrimitiveType.TRIANGLES,
			boundingSphere: BoundingSphere.fromVertices(rawPositions)
		}),
		attributes: {
			color: ColorGeometryInstanceAttribute.fromColor(Color.RED)
		}
	}),
	appearance: new PerInstanceColorAppearance({
		flat: true,
		closed: true,
		translucent: false
	}),
	asynchronous: false
});

viewer.scene.primitives.add(trianglePrimitive);