How is Vertex Rendering in Step 1 of the Rendering Pipeline overview?

OpenGL
1

Hi,
I am trying to learn OpenGL from the great online documentation available on khronos.org.

However, I am confused about the operation of the Rendering pipeline as explained in the:
Rendering Pipeline Overview
(The “Create Topic” button says I cannot post links to that (or any) page …?)

The OpenGL rendering pipeline works in the following order:

  1. Prepare vertex array data, and then render it
  2. Vertex Processing:
    …

In step 1. the part “render it” links to the Vertex Renderer which states:

Vertex Rendering is the process of taking vertex data specified in arrays and rendering one or more Primitives with this vertex data.

I guess I don’t understand what the Vertex Rendering stage really does, and I find the documentaiton about this part really unclear. Does it already uses/create primitives, and then already draws (renders) them at this stage, as the description above suggests?

Reading the rest of the steps in the Pipeline overview and the related links to the sub-topics, the generation of the stream of Primitives seems to be produced at stage 2, the Vertex processing step.

If anyone could clarify this, it would be of great help.

Thanks in advance!

2

It’s not really a “stage” in the pipeline.

Vertex setup and rendering is merely the stuff you as a user have to do to initiate the OpenGL rendering pipeline. You have to set up a VAO with arrays of vertex data, and you have to call a vertex rendering function (technically, you also need a program, along with whatever resources the program requires). Doing those things starts the rendering process. That’s why the statement links to those two pages.

3

Thank you for clarifying this. I guess it is time for me to get practical and hands on with it to get a better understanding, rather than just reading the documentation, however excellent.
Cheers!