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Fix clip coordinates/normalized device coordinates explanation
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‎03_Drawing_a_triangle/02_Graphics_pipeline_basics/01_Shader_modules.md‎

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@@ -53,23 +53,31 @@ on to the fragment shader, like color and texture coordinates. These values will
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then be interpolated over the fragments by the rasterizer to produce a smooth
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gradient.
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Clip coordinates are [homogeneous coordinates](https://en.wikipedia.org/wiki/Homogeneous_coordinates)
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A *clip coordinate* is a four dimensional vector from the vertex shader that is
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subsequently turned into a *normalized device coordinate* by dividing the whole
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vector by its last component. These normalized device coordinates are
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[homogeneous coordinates](https://en.wikipedia.org/wiki/Homogeneous_coordinates)
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that map the framebuffer to a [-1, 1] by [-1, 1] coordinate system that looks
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like the following:
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![](/images/clip_coordinates.svg)
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![](/images/normalized_device_coordinates.svg)
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You should already be familiar with these if you have dabbed in computer
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graphics before. If you have used OpenGL before, then you'll notice that the
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sign of the Y coordinates is now flipped. The Z coordinate now uses the same
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range as it does in Direct3D, from 0 to 1.
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For our first triangle we won't be applying any transformations, we'll just
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specify the positions of the three vertices directly in clip coordinates to
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create the following shape:
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specify the positions of the three vertices directly as normalized device
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coordinates to create the following shape:
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![](/images/triangle_coordinates.svg)
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We can directly output normalized device coordinates by outputting them as clip
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coordinates from the vertex shader with the last component set to `1`. That way
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the division to transform clip coordinates to normalized device coordinates will
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not change anything.
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Normally these coordinates would be stored in a vertex buffer, but creating a
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vertex buffer in Vulkan and filling it with data is not trivial. Therefore I've
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decided to postpone that until after we've had the satisfaction of seeing a

‎05_Uniform_buffers/00_Descriptor_layout_and_buffer.md‎

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@@ -93,7 +93,11 @@ Note that the order of the `uniform`, `in` and `out` declarations doesn't
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matter. The `binding` directive is similar to the `location` directive for
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attributes. We're going to reference this binding in the descriptor layout. The
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line with `gl_Position` is changed to use the transformations to compute the
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final position in clip coordinates.
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final position in clip coordinates. Unlike the 2D triangles, the last component
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of the clip coordinates may not be `1`, which will result in a division when
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converted to the final normalized device coordinates on the screen. This is used
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in perspective projection as the *perspective division* and is essential for
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making closer objects look larger than objects that are further away.
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## Descriptor set layout
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images/clip_coordinates.svg renamed to images/normalized_device_coordinates.svg

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