# Difference between Vulkan and OpenGL

Viewport:

- Y axis is flipped like D3D
- Clipped Z axis is not [-1; 1] but [0; 1]

![normalized viewport coordinates](./images/normalized_device_coordinates.svg)
![coord_sys](./images/coord_sys.png)

See: [Vulkan Tutorial (Vertex step)](https://vulkan-tutorial.com/Drawing_a_triangle/Graphics_pipeline_basics/Shader_modules) and [VK_KHR_maintenance1 (Allow negative height)](https://registry.khronos.org/vulkan/specs/latest/man/html/VK_KHR_maintenance1.html#_description)