[HOpenGL] Re: GPipe: Binding textures to geometry

[Achim Schneider]

Tobias Bexelius <tobias_bexelius at hotmail.com> wrote:

> I'm guessing you're trying to have different pictures on each side of
> the example cube? You could use a Texture3D and have an extra depth
> component for each uv-coordinate.
>
I'm rendering Glyphs, so I have a significant amount of small textures
(say, a hundred), replicated over properly positioned, orthogonal
projected geometry.

My concern is that using a Texture3D (or tiled Texture2D) would boycott
performance by forcing construction of a new texture way more often
than necessary (as I can't pre-construct the whole unicode range and
the needed glyph set will change over time), but I admittedly don't
have the numbers to back that up. I'm going to investigate.


> But you could also pair up each side with a separate texture as your
> doing now, and it will still only use one shader (but different
> sampler uniforms). For best performance however, you should put all
> six sides in a single 2D image and reference into this
> "texture-atlas".
>
From my current understanding of GPipe, using a chain of paint*
invocations invokes multiple full-screen render passes, am I correct?

In practice, rendering a single "H" reports frame times of mostly
around 1.5ms, some 5ms and a few 20-30ms. rendering "Hello, World"
takes about 20ms, and a-zA-Z0-9 a full 80ms, a thousand 'x's 1.3
seconds, spending 81% of the time in alpha-blended paintColor



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