DirectX Coordinate Spaces

I often find myself forgetting the conventions for coordinate spaces in DirectX, and for some reason I haven't found MSDN all that helpful. The DirectX 9 Projection Transform document has a nice diagram, but it's DirectX 9 specific which is now 3 versions out of date. So I wrote a tool to help me see what the conventions were. This document explains the tool and what I found. This also links together a bunch of the official MSDN documentation in a way that I find more intuitive.

DirectX provides several configuration settings that modify the behavior described here; this document attempts to describe the default behavior: I assume that if you're playing with culling or depth test settings you know how those settings change the pipeline's behavior.

Here's what we see:

With DirectX we also set a viewport. The viewport extents position the viewport in screen space (see below), and then clip space maps onto the viewport extents. Getting Started with the Rasterizer Stage is the best documentation I've found for how the viewport fits in.

The viewport maps clip space to screen space by placing the render target in screen space. The extents of clip space (the cuboid from (-1, -1, 0) to (1, 1, 1)) map to the extents of the viewport. For example, say we've set up a viewport as follows:

D3D11_VIEWPORT viewport;

viewport.Width = 200;

viewport.Height = 300;

viewport.TopLeftX = 100;

viewport.TopLeftY = 200;

viewport.MinDepth = 0.5f;

viewport.MaxDepth = 0.7f;

Then the clip space point (-1, -1, 0) will map to (100, 200) in screen space, with a depth of 0.5. The clip space point (1, 1, 1) will map to (300, 500) in screen space, with a depth of 0.7f.