ConeGeometry has wrong side faces and triangles

[longriver1012]

Description

when create the conegeometry,set the heightSegments up to 1,example 3,there is a error that side faces show only half of faces and triangles, some triangles disappear

Reproduction steps

1. Create a cone geometry
2. set the heightSegments to 3, others keep default
3. check the side faces,there is an error

Code

const geometry = new THREE.ConeGeometry(1, 1, 32, 3);
const material = new THREE.MeshBasicMaterial();
const mesh = new THREE.Mesh(geometry, material);

Live example

• jsfiddle-latest-release WebGLRenderer
• jsfiddle-dev WebGLRenderer
• jsfiddle-latest-release WebGPURenderer
• jsfiddle-dev WebGPURenderer

Screenshots

Version

r169

Device

Desktop

Browser

Chrome

OS

Windows

[Mugen87]

This is actually a regression since cone geometries like above worked with r168, see https://jsfiddle.net/vwgLxn63/.

Reverting #29460 fixes the issue.

/ping @gkjohnson

[gkjohnson]

I can make a PR in a bit - looks like I forgot to account for multiple height segments. Adjusting #29460 to the following fixes the issue. It checks if we're creating the triangles that connect to the converging point:

if ( radiusTop > 0 || y !== 0 ) {

	indices.push( a, b, d );
	groupCount += 3;

}

if ( radiusBottom > 0 || y !== heightSegments - 1 ) {

	indices.push( b, c, d );
	groupCount += 3;

}