Physically Accurate Emissive Material


I work for an arch-viz company and we are exploring the use of unreal to replace some current workflows. During the planning process we create a ZTV (Zone of theoretical visibility) where the proposed scheme is rendered with a very bright emissive material. This casts harsh shadows on the surrounding context and gives an idea of where the scheme can be seen from. Currently we use v-ray to render this. We want to use unreal so the scheme can be altered in real-time showing the effect different heights and geometry will have on the ZTV. From initial research, it looks like the emissive material in unreal is not physically accurate and its very hard to replicate the effect we want. I have created a blueprint to place point lights at the top corners of the scheme which produces what we want, but this will not be accurate as buildings will have complex geometry and many point lights will have to be placed within its volume.

Any ideas on how to create a physically accurate emissive material or any workarounds?

Thanks in advance!