kicad-developers team mailing list archive

[Mário Luzeiro <mrluzeiro@xxxxx>]

> This will lose accuracy on the board view... if I zoom in on the board
> near a character the character is correctly displayed (big)

Since it will be used for non board information, the display size can be controlled.
If it is displaying the net label, it doesn't need to zoom , it can keep the same font size on that net..

I think that Orson approach is the best for that propose, provide he controls the display size of the fonts and the best texture for the size he is rendering.

Maybe for a better texture support size, the font set can be split on multiple textures.

Mario Luzeiro
________________________________________
From: Kicad-developers [kicad-developers-bounces+mrluzeiro=ua.pt@xxxxxxxxxxxxxxxxxxx] on behalf of Maciej Sumiński [maciej.suminski@xxxxxxx]
Sent: 14 April 2016 11:02
To: Lorenzo Marcantonio
Cc: KiCad Developers
Subject: Re: [Kicad-developers] Bitmap fonts

On 04/14/2016 11:48 AM, Lorenzo Marcantonio wrote:
> On Thu, Apr 14, 2016 at 11:33:18AM +0200, Maciej Sumiński wrote:
>> Hi,
>>
>> As recently Jean-Pierre has reported he had been running out of memory
>> with complex boards, I decided to take another step to reduce memory
>> footprint of OpenGL canvas.
>>
>> Currently, the most expensive thing to draw is stroked text, as there
>> are lots of labels on tracks and pads. To reduce the drawing cost (and
>> memory requirements), texts that are not targeted to Gerber files (i.e.
>> pad & track labels) might be displayed using bitmap fonts. This way, a
>> single letter cost is reduced from tens of triangles to just two.
>
> This will lose accuracy on the board view... if I zoom in on the board
> near a character the character is correctly displayed (big), to have
> such resolution on a bitmap font you'll need a huge texture map. OTOH
> antialiased bitmap would be actually more readable than the current
> unconsistent-stroke-width one. Also you need quite a bit of a texture to
> contain the current repository (IIRC it's most of the latin space plus
> some greek plus some cyrillic).

I would argue if an enormous texture is a requirement. Currently the
code uses 2048 x 2048 @ 8-bit atlas [1], and I hope it can be supported
by the majority of popular GPUs. If you check, the atlas contains also
cyrillic, greek and what-not characters. You have to really zoom in to
see distortions resulting from using bitmap fonts.

Alternatively, there is 1024 x 1024 version too, but I would rather
switch to it, if I am wrong about my GPU capabilities prediction.

> Surely it is a good solution for non-design text, like net names and pin
> numbers; I'd make it optional for design text like silk and copper text.
>
> The performance issue is expected since 'modern' GPUs are biased versus
> texture pulling rather than geometry computation (the old FireGLs had an
> extremely idiotic texture unit but a blazing fast geometry coprocessor
> --- for the time, of course; and an hardware overlay bitplane :D)
>
> Could be worth a try; otherwise some more refined kind of view/LoD
> culling would be needed (changing during pan/zoom the visible geometry);
> definitely a lot more complex.

There is already a level-of-detail culling implemented. It was really
necessary to render net/pad names on complex board. Otherwise
performance was really poor.

> Another simple thing I suggested a while ago but didn't actually try:
> why don't use line strips for non-design text? That would be reasonable
> (2 point for segment), completely zoomable; you lose control of the line
> width (since for some reason many GPU have arbitrary limits on line
> width... 5px on the Intels IIRC) but it would be a lot better than
> textured text.

5 px is quite a limitation, do not you think? I would rather increase
the atlas texture resolution or split it into a few textures.

Regards,
Orson

1.
https://raw.githubusercontent.com/orsonmmz/kicad-source-mirror/97d20a1f279f6f3f051b440bbd8aaab7e38fcde9/helpers/gal_bitmap_font/bitmap_font_2048_0.png
2.
https://github.com/orsonmmz/kicad-source-mirror/blob/97d20a1f279f6f3f051b440bbd8aaab7e38fcde9/helpers/gal_bitmap_font/bitmap_font_0.png