Cone Geometry and Cylinder Geometry

They are almost Same. 😃

• The Basic Syntax of Cylinder Geometry is CylinderGeometry(radiusTop : Float, radiusBottom : Float, height : Float, radialSegments : Integer, heightSegments : Integer, openEnded : Boolean, thetaStart : Float, thetaLength : Float).
• Here radiusTop and radiusBottom are the radius of the top end and bottom end respectively. Default: 1 for both .
• height of the cylinder is as shown below. Default: 1

• radialSegments are the number of segmented faces along the circumference of the cylinder. Default: 8.
• heightSegments are the number of rows of faces along the height of the cylinder. Default: 1.
• openEnded is the boolean value that determines if the cylinder should be open or closed/capped. It basically removes the top and bottom faces.

• thetaStart is the start angle of the first segment that is generated. Default: 0.
• thetaLength is the angle of the sector that we want to create. Default: Math.PI * 2.

By now you would have guessed that if we have either radiusTop or radiusBottom as 0 then we will get a Cone.😄😄

Now for Cone Geometry: ConeGeometry(radius : Float, height : Float, radialSegments : Integer, heightSegments : Integer, openEnded : Boolean, thetaStart : Float, thetaLength : Float).

• radius is the radius of the Cone. Default: 1.
• height is the length of height of the Cone. Default: 1.

  radialSegments, heightSegments, openEnded, thetaStart & thetaLength are the same as that in cylinder.

• radialSegments are the number of segmented faces along the circumference of the cylinder. Default: 8.
• heightSegments are the number of rows of faces along the height of the cylinder. Default: 1.
• openEnded is the boolean value that determines if the cylinder should be open or closed/capped. It basically removes the top and bottom faces.
• thetaStart is the start angle of the first segment that is generated. Default: 0.
• thetaLength is the angle of the sector that we want to create. Default: Math.PI * 2.

In the below code try changing the parameters as CylinderGeometry( 5, 0, 20, 32, 1, false, 0, Math.PI * 2).

See that when we change the value to CylinderGeometry( 5, 5, 20, 32, 1, false, 0, Math.PI). Then we get a part/sector of Cylinder.

const cylinderGeometry = new THREE.CylinderGeometry( 5, 5, 20, 32, 1, false, 0, Math.PI * 2);
const cylinderMaterial = new THREE.MeshNormalMaterial( {flatShading: true} );
const cylinder = new THREE.Mesh( cylinderGeometry, cylinderMaterial );
cylinder.position.x = -15;
cylinder.position.y = 0;
cylinder.position.z = 0;
cylinder.rotation.x = Math.PI / 2;
scene.add( cylinder );

const coneGeometry = new THREE.ConeGeometry(5, 20, 32);
const coneMaterial = new THREE.MeshNormalMaterial( {flatShading: true} );
const cone = new THREE.Mesh(coneGeometry, coneMaterial);
cone.position.x = 15;
cone.position.y = 0;
cone.position.z = 0;
cone.rotation.x = -Math.PI / 2;
scene.add( cone );


animate();

function animate() {
      requestAnimationFrame(animate);
      cylinder.rotation.x += 0.01;
      cylinder.rotation.y += 0.01;
      cylinder.rotation.z += 0.01;
      cone.rotation.x += 0.01;
      cone.rotation.y += 0.01;
      cone.rotation.z += 0.01;
      renderer.render(scene, camera);
}

Final:

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