Distance font rendering

One drawback to using bitmap font is that it shows significant aliasing when the font is scaled. Therefore, fonts such as small, normal, big, and so on will usually be created for a particular font to cope with different scaling intervals.

This can create a huge memory overhead. The article Http://www.valvesoftware.com/publications/2007/SIGGRAPH2007_AlphaTestedMagnification.pdf of value refers to a

Scale friendly method, the result of the implementation is as follows.

Implementation method:

1. Use FreeType, or Windows GDI to create a bitmap of characters. The super-sample is used here. For fonts with a base 20 height, use a font of X Supersamplescale to create bitmaps. It is created in the X 4来.

2. For each character of the bitmap, convert and down the scale to signed distance field. It is important to note that in Bitmap-font we always store and render characters in the smallest bounding box of a character bitmap. But for distance field, you must

Large expansion of the perimeter of the bounding box of the character. For example, the bitmap size of ' A ' is 16x20, so for the creation of distance field, we have to expand to (16+paddingx*2) * (+paddingy*2), and then put the character bitmap in the middle position after the

Distance calculation. Otherwise, in texture sampling, linear filtering should cause the edges of the characters to cross over adjacent characters.

3. Convert the distance after the down scale to a bitmap and pack the storage.

Basically now the article that the Google comes out is to deal with a whole package of bitmap, for example:

Https://github.com/libgdx/libgdx/wiki/Distance-field-fonts

https://crimild.wordpress.com/2013/09/01/improving-text-rendering-with-signed-distance-fields/

https://www.mapbox.com/blog/text-signed-distance-fields/

This way I feel a problem, it requires that the characters are very sparse in Atlas, and carefully specify a sweep radius to ensure that the distance is not affected by other characters in the area of a character.

, due to the problem of arranging and scanning radii, the pixels that surround the a character, the Red line mark area, and the nearest edge computed by its distance may be located on the G character. There will be incorrect results when rendering.

Adjusts the scan radius and the processing results after padding.

• . The singed distance field font has a good effect when zoomed in, but it is very ugly when the font shrinks.
• About Smoothstep.

Smoothstep (0.5-smoothbais, 0.5 + Smoothbais, Distance);

The value of Smoothbais can severely affect the final rendering quality. I finally chose the fontheight/texturesize. Smoothbais is a data that follows the texture size and is more sensitive to sampling patterns, and may be better with DDX Ddy.

Wip:

• Render quality.
• Glow & Shadow.

Distance font rendering