Merge 0.4.15 changes into stable-0.4

0.4.15 release!

1 files changed, 14 insertions, 2 deletions

diff --git a/client/shaders/wielded_shader/opengl_fragment.glsl b/client/shaders/wielded_shader/opengl_fragment.glsl
index 75dd1b674..ba7a8f12d 100644
--- a/client/shaders/wielded_shader/opengl_fragment.glsl
+++ b/client/shaders/wielded_shader/opengl_fragment.glsl
@@ -19,6 +19,8 @@ bool texSeamless = false;
 
 const float e = 2.718281828459;
 const float BS = 10.0;
+const float fogStart = FOG_START;
+const float fogShadingParameter = 1 / ( 1 - fogStart);
 
 void get_texture_flags()
 {
@@ -107,8 +109,18 @@ void main(void)
 	vec4 col = vec4(color.rgb, base.a);
 	col *= gl_Color;
 	if (fogDistance != 0.0) {
-		float d = max(0.0, min(vPosition.z / fogDistance * 1.5 - 0.6, 1.0));
-		col = mix(col, skyBgColor, d);
+		// Due to a bug in some (older ?) graphics stacks (possibly in the glsl compiler ?),
+		// the fog will only be rendered correctly if the last operation before the
+		// clamp() is an addition. Else, the clamp() seems to be ignored.
+		// E.g. the following won't work:
+		//      float clarity = clamp(fogShadingParameter
+		//		* (fogDistance - length(eyeVec)) / fogDistance), 0.0, 1.0);
+		// As additions usually come for free following a multiplication, the new formula
+		// should be more efficient as well.
+		// Note: clarity = (1 - fogginess)
+		float clarity = clamp(fogShadingParameter
+			- fogShadingParameter * length(eyeVec) / fogDistance, 0.0, 1.0);
+		col = mix(skyBgColor, col, clarity);
 	}
 	gl_FragColor = vec4(col.rgb, base.a);
 }