简单地形索引公式[转自龙书]

简单地形索引公式:

三角形 ABC = Vector3(i*_numVertsPerRow+j, i*_numVertsPerRow+j+1, (i+1)*_numVertsPerRow+j);
三角形 CBD = Vector3((i+1)*_numVertsPerRow+j, i*_numVertsPerRow+j+1, (i+1)*_numVertsPerRow+j+1);