Vulkan is a new API by the Khronos group (known for OpenGL) that provides a much better abstraction of modern graphics cards.
Coordinate system
For vulkan, the Normalized Device Coordinates (NDC) are:
(-1, -1) (1, -1)
+--------+
| |
| |
| |
| |
+--------+
(-1, 1) (1, 1)