Abstract. Ninety per cent of urban areas' total noise pollution is caused by traffic. Green areas are a very important factor for noise reduction. They will absorb noise from 5dB (A) to 10 dB (A). Nonetheless, some major concerns can be addressed, such as: how can green areas be established in the urban city?, how trees absorb noise?, what are the equations to calculate noise absorption by trees?, and what are the best survey methods to measure the trees' properties?, and is it possible to visualize trees in three-dimensional (3D) space?. Thirty-five (35) research papers were selected under the subtopics, green spaces and urban forms, noise absorption by green spaces, and green spaces visualization in 3D to find solutions for the above problems. The review has identified how to increase green spaces in urban forms like core, star, satellite, and linear. Next, the leaves are the main possible part to absorb noise, and depend on the leaves' surface area, tree depth, and noise absorption coefficient. These parameters must be considered to formulate an equation to identify sound absorption by leaves. Furthermore, the Light Detection and Ranging (LiDAR) technique can be used for determining the surface area of leaves and tree depth, due to its high resolution of point clouds. The Digital Surface Model (DSM) is not applicable for visualizing green areas, because it represents the only top view of trees, and tree depth cannot be identified properly. Proper visualization of green spaces in 3D will convey a significant point of view to visualize noise absorption accurately in a 3D urban city.

Abstract. Voxelization of data is discretizing the 3D space, in which the simplest form is a single voxel. There is a large number of publications that are related to voxelization. However, this paper focuses on the voxelization technique implemented in 3D building modelling. This paper aims to get the development idea of the voxelization technique throughout these past years to determine the suitable technique and method for including a 3D voxelized building model in Computational Fluid Dynamics (CFD). From the search and analysis, it is found that this technique is not only related to data modelling of the 3D voxelized model; the voxelization technique can also be utilized in the data segmentation process. First, for the data segmentation, the voxelization technique is implemented to manage the large amount of point cloud data that were obtained from the 3D scanner and sensors, which is done by reducing the number of data to avoid data redundancy and unused data using each of the voxels that exist in that environment. Second, for data modelling, popular input data to generate the 3D voxelized model is also in the form of a point cloud. However, there are still other forms, such as line and surface. Nevertheless, this paper reviews the voxelized technique in building modelling despite some data segmentation. The review shows various input data, applications, and techniques associated with the voxelization process based on building model generation. However, there is still room for improvement that allows the 3D model to be modelled in the voxelized form in the CFD domain.

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