quakeforge/libs/video/renderer/glsl/quaketxt.vert

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uniform mat4 mvp_mat;
/** Vertex position.
x, y, cx, cy
\a vertex provides the onscreen location at which to draw the character
(\a x, \a y) and which corner of the character cell this vertex
represents (\a cx, \a cy). \a cx and \a cy must be either 0 or 1, or
wierd things will happen with the character cell.
*/
attribute vec4 vertex;
/** The character to draw.
The quake character map supports only 256 characters, 0-255. Any other
value will give interesting results.
*/
attribute float char;
/** Coordinate in character map texture.
*/
varying vec2 st;
void
main (void)
{
float row, col;
vec2 pos, corner, uv;
const vec2 inset = vec2 (0.03125, 0.03125);
const vec2 size = vec2 (0.0625, 0.0625);
row = floor (char / 16.0);
col = mod (char, 16.0);
pos = vertex.xy;
corner = vertex.zw;
uv = vec2 (col, row) + inset * (1.0 - 2.0 * corner) + corner;
uv *= size;
gl_Position = mvp_mat * vec4 (pos + corner * 8.0, 0.0, 1.0);
st = uv;
}