确定
MaterialAppearance 实例支持的 Material 类型。这是在灵活性（广泛的材质选择）与内存/性能（所需的顶点格式和GLSL着色器复杂度）之间的权衡。Members
static constant Cesium.MaterialAppearance.MaterialSupport.ALL : MaterialAppearance.MaterialSupportType
All materials, including those that work in tangent space, are supported.
This requires
position, normal, st,
tangent, and bitangent vertex attributes.
static constant Cesium.MaterialAppearance.MaterialSupport.BASIC : MaterialAppearance.MaterialSupportType
仅支持基础材质，仅需
position 和 normal 顶点属性。
static constant Cesium.MaterialAppearance.MaterialSupport.TEXTURED : MaterialAppearance.MaterialSupportType
Materials with textures, which require
position,
normal, and st vertex attributes,
are supported. The vast majority of materials fall into this category.