靠近建築物外所種植的樹木，通常會影響室內採光，枝葉的分布有如百葉窗一般，會對光線有遮擋、穿透、反射、散射的影響；在真實世界中，樹冠疏密程度對光的影響可從視覺感官感受，但在電腦模擬時卻少有表現樹冠特性，若能在光環境模擬時加入樹冠特性，將會對光環境有更真實、準確的模擬。
樹冠影響光環境的三種尺度，分別為樹冠和建築物的距離，樹冠透光率，以及單株枝葉的透光率，本研究以樹冠透光率為出發點，以建立透光率實驗及建模方法為中心，實驗分為二大部份，首先是透光率實驗，目的為分析不同樹種透光率與樹冠特性，第二部分是樹冠模型測試，先實測真實樹冠，再將實驗所得之透光率放於模擬軟體中，將模擬與實驗所得輝度結果做比較。
在第一部分實驗後，分析四個不同樹種的透光率，得到透光率線段的趨勢，也將透光率和密度做比較，發現枝葉密度會影響光線穿透，但並非所有樹種的枝葉密度都與透光率有高度相關，枝葉較分散稀疏的樹，密度與透光率的相關性低。第二部分的實驗結果發現，因實驗時的天氣狀況在模擬時無法詳細描述出來，因此實驗點的11 個輝度值差距大，僅由立面窗口的輝度值比例來比較。
本研究利用魚眼鏡頭及HDR 照片取得透光率，用來製作樹冠模型或進行透光特性分析，日後可沿用此實驗方法於其他樹種，並應用於室內空間光環境模擬。

The position of trees outside of a building will impact indoor lighting. The
distribution of tree branches and leaves are similar to shutter, it will block the light and influence penetration, reflection, and scattering of the light. In our daily life, we can use our sensory organs to feel the change in light because of the tree canopy density. There is only little research conducted with computer simulation method for analyzing the characteristics of light related to tree canopy. If the tree canopy characteristics can be added into the light environment computer simulation, it will create more realistic and accurate light environment simulation.
There are three main factors that tree canopy can affect light environment: the
distance between tree canopy and a building, the tree canopy transmittance rate,
and the transmittance rate of single branch. This study only focused on the tree
canopy transmittance rate. The experiment is separated into two parts; the first one is transmittance rate for analyzing light transmittance and tree canopy characteristics with different types of trees. The second one is tree canopy model testing to obtain the light transmittance of tree canopy, which will be used in computer simulation and in the end, compared the luminance results between experiment and simulation.
In this study, fisheye lens and HDR photo are the instruments to obtain the light transmittance for creating canopy model or analysis characteristics of light transmittance. This experimental method can be applied to other species of tree and indoor light environment simulation.

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