fix vertex normal generation error
fix vertex normal generation error

AnySDK/EarthWarrior3D,AnySDK/EarthWarrior3D,yylangchen/EarthWarrior3D,AnySDK/EarthWarrior3D,yylangchen/EarthWarrior3D,yylangchen/EarthWarrior3D,yylangchen/EarthWarrior3D,AnySDK/EarthWarrior3D,AnySDK/EarthWarrior3D,yylangchen/EarthWarrior3D