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I would like to render game UI, and for that I need rectangles. However, since a button could be textured just as well as solid color or (multistop)gradient a problem arises. I would also like all types of rectangles(buttons) somehow at least partially uniform at handling.
I have been puzzled by this issue for quite a time and idea came across my mind - what if I stored colors to a 1D texture array and treat all rectangles as textured. Could you give me some example how to do this? Or event better a reason not-to solve it this way and point to better solution?

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  • \$\begingroup\$ Why not just use a vertex attribute? \$\endgroup\$
    – API-Beast
    Commented Aug 10, 2014 at 11:47
  • \$\begingroup\$ Vertex attribute would require unnecessary data(each vertex would have to get both color and UV) and either additional math or condition jump. Remember - rectangle can have either texture or color. \$\endgroup\$
    – wondra
    Commented Aug 10, 2014 at 11:56
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    \$\begingroup\$ You don't need condition jump, a invalid texture (texture index 0) is always 100% white. This seems to be a very premature optimization to me. \$\endgroup\$
    – API-Beast
    Commented Aug 10, 2014 at 12:14
  • \$\begingroup\$ +1, I didnt know that about 0 texture. However, this is not much about optimization but the goal was to have a rectangle that can be processed exactly same way regardless background type as background is irrelevant for other (GUI) logic. \$\endgroup\$
    – wondra
    Commented Aug 10, 2014 at 12:28
  • \$\begingroup\$ @API-Beast i'm afraid that's not always true: on my gpu/implementation/whatever, a 0 texture acts as if it's filled with zeroes (which would be black and 100% transparent as RGBA). this also makes for interesting effects if used with compositing window managers (I can actually render holes into the window) \$\endgroup\$
    – nonchip
    Commented Sep 13, 2014 at 5:55

1 Answer 1

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You could do this:

  • Create a texture holding all the colors you want.

  • For the actual button geometry, set the texture coordinates to the appropriate region of the color texture (they can all be the same value, in fact).

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  • \$\begingroup\$ And what if I dont know in advance how many colors(and which) do I need? Is better to use 1d array, rectangle texture or just classic 2d texture? \$\endgroup\$
    – wondra
    Commented Aug 10, 2014 at 11:18
  • \$\begingroup\$ Doesn't matter, really; in all cases you'd need to add the new texels to the texture. \$\endgroup\$
    – user1430
    Commented Aug 10, 2014 at 17:19

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