# Objective
PBR lighting was broken in the new renderer when using orthographic projections due to the way the depth slicing works for the clusters. Fix it.
## Solution
- The default orthographic projection near plane is 0.0. The perspective projection depth slicing does a division by the near plane which gives a floating point NaN and the clustering all breaks down.
- Orthographic projections have a linear depth mapping, so it made intuitive sense to me to do depth slicing with a linear mapping too. The alternative I saw was to try to handle the near plane being at 0.0 and using the exponential depth slicing, but that felt like a hack that didn't make sense.
- As such, I have added code that detects whether the projection is orthographic based on `projection[3][3] == 1.0` and then implemented the orthographic mapping case throughout (when computing cluster AABBs, and when mapping a view space position (or light) to a cluster id in both the rust and shader code).
## Screenshots
Before:
After:
<img width="1392" alt="Screenshot 2021-12-13 at 16 36 53" src="https://user-images.githubusercontent.com/302146/145847314-6f3a2035-5d87-4896-8032-0c3e35e15b7d.png">
Old renderer (slightly lighter due to slight difference in configured intensity):
<img width="1392" alt="Screenshot 2021-12-13 at 16 42 23" src="https://user-images.githubusercontent.com/302146/145847391-6a5e6fe0-22da-4fc1-a6c7-440543689a63.png">
c061ec33c8
