| #version 150 core |
| |
| uniform sampler2D distanceFieldTexture; |
| uniform float minAlpha; |
| uniform float maxAlpha; |
| uniform float textureSize; |
| uniform vec4 color; |
| |
| in vec2 texCoord; |
| in float zValue; |
| |
| out vec4 fragColor; |
| |
| void main() |
| { |
| // determine the scale of the glyph texture within pixel-space coordinates |
| // (that is, how many pixels are drawn for each texel) |
| vec2 texelDeltaX = abs(dFdx(texCoord)); |
| vec2 texelDeltaY = abs(dFdy(texCoord)); |
| float avgTexelDelta = textureSize * 0.5 * (texelDeltaX.x + texelDeltaX.y + texelDeltaY.x + texelDeltaY.y); |
| float texScale = 1.0 / avgTexelDelta; |
| |
| // scaled to interval [0.0, 0.15] |
| float devScaleMin = 0.00; |
| float devScaleMax = 0.15; |
| float scaled = (clamp(texScale, devScaleMin, devScaleMax) - devScaleMin) / (devScaleMax - devScaleMin); |
| |
| // thickness of glyphs should increase a lot for very small glyphs to make them readable |
| float base = 0.5; |
| float threshold = base * scaled; |
| float range = 0.06 / texScale; |
| |
| float minAlpha = threshold - range; |
| float maxAlpha = threshold + range; |
| |
| float distVal = texture(distanceFieldTexture, texCoord).r; |
| fragColor = vec4(color.rgb, color.a * smoothstep(minAlpha, maxAlpha, distVal)); |
| gl_FragDepth = gl_FragCoord.z - zValue * 0.000001; |
| } |