WebGL_0006：PlayCan替换材质和贴图的方法

                // 6 9 0 10 8
                // this.body2.model.model.meshInstances[22].material.emissive = new pc.Color(255, 0, 0);
                // 替换材质
                mod.body.model.model.meshInstances[6].material = mod.MB_Mat[0].resource;
                mod.body.model.model.meshInstances[9].material = mod.MB_Mat[1].resource;
                mod.body.model.model.meshInstances[0].material = mod.MB_Mat[2].resource;
                mod.body.model.model.meshInstances[10].material = mod.MB_Mat[3].resource;
                // 替换贴图
                mod.MB_Mat[4].resource && (mod.MB_Mat[4].resource.diffuseMap = mod.MB_Tex[0].resource, mod.MB_Mat[4].resource.emissiveMap = mod.MB_Tex[0].resource, mod.MB_Mat[4].resource.update());