1 files changed, 38 insertions, 0 deletions
diff --git a/src/extras/shaders/gl3/distancefieldtext.frag b/src/extras/shaders/gl3/distancefieldtext.frag
new file mode 100644
index 000000000..4f0c9cac0
--- /dev/null
+++ b/src/extras/shaders/gl3/distancefieldtext.frag
@@ -0,0 +1,38 @@
+#version 150 core
+
+uniform sampler2D distanceFieldTexture;
+uniform float minAlpha;
+uniform float maxAlpha;
+uniform float textureSize;
+uniform vec4 color;
+
+in vec3 position;
+in vec2 texCoord;
+
+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 = color * smoothstep(minAlpha, maxAlpha, distVal);
+}