intersectTriangle method

Vector3? intersectTriangle(Map<String, Vector3> triangle, bool backfaceCulling, Vector3 result)

Performs a ray/triangle intersection test and stores the intersection point to the given 3D vector. If no intersection is detected, null is returned.

Implementation

Vector3? intersectTriangle(Map<String,Vector3> triangle, bool backfaceCulling, Vector3 result ) {
	// reference: https://www.geometrictools.com/GTEngine/Include/Mathematics/GteIntrRay3Triangle3.h
	final a = triangle['a']!;
	final b = triangle['b']!;
	final c = triangle['c']!;

	edge1.subVectors( b, a );
	edge2.subVectors( c, a );
	normal.crossVectors( edge1, edge2 );

	double ddN = direction.dot( normal );
	int sign;

	if ( ddN > 0 ) {
		if ( backfaceCulling ) return null;
		sign = 1;
	}
    else if ( ddN < 0 ) {
		sign = - 1;
		ddN = - ddN;
	}
    else {
		return null;
	}

	v1.subVectors( origin, a );
	final ddQxE2 = sign * direction.dot( edge2.crossVectors( v1, edge2 ) );

	// b1 < 0, no intersection
	if ( ddQxE2 < 0 ) {
		return null;
	}

	final ddE1xQ = sign * direction.dot( edge1.cross( v1 ) );

	// b2 < 0, no intersection
	if ( ddE1xQ < 0 ) {
		return null;
	}

	// b1 + b2 > 1, no intersection
	if ( ddQxE2 + ddE1xQ > ddN ) {
		return null;
	}

	// line intersects triangle, check if ray does
	final qdN = - sign * v1.dot( normal );

	// t < 0, no intersection
	if ( qdN < 0 ) {
		return null;
	}

	// ray intersects triangle
	return at( qdN / ddN, result );
}