three
Version:
JavaScript 3D library
107 lines (73 loc) • 2.14 kB
JavaScript
import Node from '../core/Node.js';
import { nodeImmutable, float, Fn } from '../tsl/TSLBase.js';
import { BackSide, DoubleSide, WebGLCoordinateSystem } from '../../constants.js';
/**
* This node can be used to evaluate whether a primitive is front or back facing.
*
* @augments Node
*/
class FrontFacingNode extends Node {
static get type() {
return 'FrontFacingNode';
}
/**
* Constructs a new front facing node.
*/
constructor() {
super( 'bool' );
/**
* This flag can be used for type testing.
*
* @type {boolean}
* @readonly
* @default true
*/
this.isFrontFacingNode = true;
}
generate( builder ) {
if ( builder.shaderStage !== 'fragment' ) return 'true';
//
const { renderer, material } = builder;
if ( renderer.coordinateSystem === WebGLCoordinateSystem ) {
if ( material.side === BackSide ) {
return 'false';
}
}
return builder.getFrontFacing();
}
}
export default FrontFacingNode;
/**
* TSL object that represents whether a primitive is front or back facing
*
* @tsl
* @type {FrontFacingNode<bool>}
*/
export const frontFacing = /*@__PURE__*/ nodeImmutable( FrontFacingNode );
/**
* TSL object that represents the front facing status as a number instead of a bool.
* `1` means front facing, `-1` means back facing.
*
* @tsl
* @type {Node<float>}
*/
export const faceDirection = /*@__PURE__*/ float( frontFacing ).mul( 2.0 ).sub( 1.0 );
/**
* Converts a direction vector to a face direction vector based on the material's side.
*
* If the material is set to `BackSide`, the direction is inverted.
* If the material is set to `DoubleSide`, the direction is multiplied by `faceDirection`.
*
* @tsl
* @param {Node<vec3>} direction - The direction vector to convert.
* @returns {Node<vec3>} The converted direction vector.
*/
export const directionToFaceDirection = /*@__PURE__*/ Fn( ( [ direction ], { material } ) => {
const side = material.side;
if ( side === BackSide ) {
direction = direction.mul( - 1.0 );
} else if ( side === DoubleSide ) {
direction = direction.mul( faceDirection );
}
return direction;
} );