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  • $\begingroup$ Thank you so much for the explanation! After writing this post I did come to the conclusion that I was supposed to render a box "inside out" but the "inside out" part I wasn't sure what was meant, so your advice to flip the normals clarified that. I am also additively blending. Now at this point I have the box rendering at world position (0,0,0) with the normals flipped. I am using the camera view and position in world space for now just to be safe and since the box is at (0, 0, 0) I should be fine. (continued) $\endgroup$ Commented Oct 13, 2021 at 20:40
  • $\begingroup$ Now the last question I have is, what value am I supposed to pass to pobject? From the book explanation, it sounds like I need to pass the current pixel position of the pixel that the box shader is currently rendering. But reading the comment above the description of the function it says: "This shader renders a halo effect of radius R at the object-space position pobject." so it makes it sound like in my case, I should pass (0,0,0). I tried both and neither give the result of rendering the basic shape of the halo. $\endgroup$ Commented Oct 13, 2021 at 20:40
  • $\begingroup$ Also I should mention, if I pass (0,0,0) to pobject, the result I get seem to be correct in the case where the camera is inside the radius R. If the camera steps outside of this radius, nothing is rendered. $\endgroup$ Commented Oct 13, 2021 at 20:52
  • $\begingroup$ pobject is the position values of the object which is the cube that is being rendered. So compute gl_Position using the mvp matrix and pass the the pobject values down to the fragment shader. $\endgroup$ Commented Oct 13, 2021 at 21:30
  • $\begingroup$ I used the pixel world position and it seems to (almost) work! I updated my post with the details. $\endgroup$ Commented Oct 14, 2021 at 5:11