3
$\begingroup$

I'm not sure if this is the proper community to ask this question. Feel free to move it if not, thanks.

I want to simulate an old CRT screen using 3D libraries. My question would be: Which geometrical object is the most similar to the surface of a CRT screen? (Or is it non-regular?)

If I know the answer for this, then I guess it will be easy to find the equations on the internet, so that is not required, although I would be grateful. I would prefer surfaces, which can be changed by multiple parameters, so some sort of fine-tuning is possible.

Many thanks!

UPDATE:

These are some example CRTs:

In case one would try to combine multiple geometric shapes, how is it possible to still have round edges where they meet. For example one could join these two ellipses, by always choosing the highest point for each vertical line:

Combine 2 ellipses

But then there would be edges at the blue dots.

  • 0
    Please post a picture of what you want, with an explicit enumeration of the surface(s). – 2017-01-02
  • 0
    @Yves Daoust: done – 2017-01-02
  • 0
    Sorry, you dit not enumerate the surfaces. – 2017-01-02
  • 0
    @Yves Daoust: You mean example surface pairs, which could be joined? I think that's not that important. I would be more curios about a general technique for joining them. (like cylinders, ellipsoids, etc.) – 2017-01-02

1 Answers 1

3

From this link:

The three most common CRT shapes are spherical (a section of a sphere, used in the oldest and most inexpensive monitors), cylindrical (a section of a cylinder, used in aperture-grille CRTs), and flat square (a section of a sphere large enough to make the screen nearly flat).

I suggest you use a section of a vertical cylinder, so that there is no curvature vertically, but a slight horizontal bending.

From this link:

Trinitron is Sony technology. The shadow mask ... is always straight in the vertical direction and curved in the horizontal direction, thus the shape is a cylinder. The tube surface is also cylindrical, ...

  • 1
    The surface can be rounded at edges, requiring additional spherical, cylindrical and toroidal patches. – 2017-01-02
  • 0
    Thanks, I could try that, although I have the feeling that this has vertical curvature too: https://www.youtube.com/watch?v=eSw0fcCaWqA – 2017-01-02
  • 0
    @Yves Daoust: is there a general way to "implement" these "patches"? Maybe with min/max over the two shapes? – 2017-01-02
  • 0
    @CrouchingKitten: what are the geometric primitives supported by your modeler ? – 2017-01-02
  • 0
    @Yves Daoust: I plan to implement it as a vertex shader, so it will map coordinates with an algorithm. Since I will only display characters, it's also possible to implement it by generating the corner-coordinates of rectangular polygons for each character. (the second solution can be done on the normal CPU) – 2017-01-02
  • 0
    On the shown samples, the edges are hidden behind a frame. In this case forget my other comment. (But now the frame has planar and cylindrical/conic patches.) Are you familiar with parametric equations of the surfaces ? - @joseph: sorry to clutter your post. – 2017-01-02
  • 0
    @Yves Daoust: yes, parametric equations would be the best. Like: (x1, y1, 0) -> (x2, y2, z2) – 2017-01-02
  • 0
    @Yves Daoust: now the closest thing i could implement is an ellipsoid, although I have the feeling that it wouldn't be the same. If I would try to combine objects with min/max, then there would be a sharp edge where they meet. – 2017-01-02
  • 0
    "to combine objects with min/max": no idea what you mean. Explain that in your post if you want. – 2017-01-02