diff --git a/code/renderergl2/glsl/lightall_fp.glsl b/code/renderergl2/glsl/lightall_fp.glsl
index b983d6fef6..871c527e34 100644
--- a/code/renderergl2/glsl/lightall_fp.glsl
+++ b/code/renderergl2/glsl/lightall_fp.glsl
@@ -167,7 +167,7 @@ vec3 EnvironmentBRDF(float gloss, float NE, vec3 specular)
 	return clamp( a0 + specular * ( a1 - a0 ), 0.0, 1.0 );
   #elif 0
 	// from http://seblagarde.wordpress.com/2011/08/17/hello-world/
-	return mix(specular.rgb, max(specular.rgb, vec3(gloss)), CalcFresnel(NE));
+	return specular + CalcFresnel(NE) * clamp(vec3(gloss) - specular, 0.0, 1.0);
   #else
 	// from http://advances.realtimerendering.com/s2011/Lazarov-Physically-Based-Lighting-in-Black-Ops%20%28Siggraph%202011%20Advances%20in%20Real-Time%20Rendering%20Course%29.pptx
 	return mix(specular.rgb, vec3(1.0), CalcFresnel(NE) / (4.0 - 3.0 * gloss));
@@ -379,7 +379,7 @@ void main()
 	N.xy = texture2D(u_NormalMap, texCoords).rg - vec2(0.5);
     #endif
 	N.xy *= u_EnableTextures.x;
-	N.z = sqrt((0.25 - N.x * N.x) - N.y * N.y);
+	N.z = sqrt(clamp((0.25 - N.x * N.x) - N.y * N.y, 0.0, 1.0));
 	N = tangentToWorld * N;
   #else
 	N = var_Normal.xyz;
@@ -473,7 +473,21 @@ void main()
   #endif
 
 	gl_FragColor.rgb  = lightColor   * reflectance * NL;
+
+#if 0
+	vec3 aSpecular = EnvironmentBRDF(gloss, NE, specular.rgb);
+
+	// do ambient as two hemisphere lights, one straight up one straight down
+	float hemiDiffuseUp    = N.z * 0.5 + 0.5;
+	float hemiDiffuseDown  = 1.0 - hemiDiffuseUp;
+	float hemiSpecularUp   = mix(hemiDiffuseUp, float(N.z >= 0.0), gloss);
+	float hemiSpecularDown = 1.0 - hemiSpecularUp;
+
+	gl_FragColor.rgb += ambientColor * 0.75 * (diffuse.rgb * hemiDiffuseUp   + aSpecular * hemiSpecularUp);
+	gl_FragColor.rgb += ambientColor * 0.25 * (diffuse.rgb * hemiDiffuseDown + aSpecular * hemiSpecularDown);
+#else
 	gl_FragColor.rgb += ambientColor * (diffuse.rgb + specular.rgb);
+#endif
 
   #if defined(USE_CUBEMAP)
 	reflectance = EnvironmentBRDF(gloss, NE, specular.rgb);
diff --git a/code/renderergl2/glsl/shadowmask_fp.glsl b/code/renderergl2/glsl/shadowmask_fp.glsl
index 4bac5ccdd8..b489fef549 100644
--- a/code/renderergl2/glsl/shadowmask_fp.glsl
+++ b/code/renderergl2/glsl/shadowmask_fp.glsl
@@ -18,6 +18,10 @@ uniform vec4   u_ViewInfo; // zfar / znear, zfar
 varying vec2   var_DepthTex;
 varying vec3   var_ViewDir;
 
+// depth is GL_DEPTH_COMPONENT24
+// so the maximum error is 1.0 / 2^24
+#define DEPTH_MAX_ERROR 0.000000059604644775390625
+
 // Input: It uses texture coords as the random number seed.
 // Output: Random number: [0,1), that is between 0.0 and 0.999999... inclusive.
 // Author: Michael Pohoreski
@@ -39,7 +43,7 @@ float PCF(const sampler2D shadowmap, const vec2 st, const float dist)
 {
 	float mult;
 	float scale = 2.0 / r_shadowMapSize;
-		
+
 #if defined(USE_SHADOW_FILTER)
 	float r = random(var_DepthTex.xy);
 	float sinr = sin(r) * scale;
@@ -71,6 +75,7 @@ float PCF(const sampler2D shadowmap, const vec2 st, const float dist)
 float getLinearDepth(sampler2D depthMap, vec2 tex, float zFarDivZNear)
 {
 		float sampleZDivW = texture2D(depthMap, tex).r;
+		sampleZDivW -= DEPTH_MAX_ERROR;
 		return 1.0 / mix(zFarDivZNear, 1.0, sampleZDivW);
 }
 
@@ -81,7 +86,7 @@ void main()
 	float depth = getLinearDepth(u_ScreenDepthMap, var_DepthTex, u_ViewInfo.x);
 	float sampleZ = u_ViewInfo.y * depth;
 
-	vec4 biasPos = vec4(u_ViewOrigin + var_ViewDir * depth * 0.99, 1.0);
+	vec4 biasPos = vec4(u_ViewOrigin + var_ViewDir * (depth - 0.5 / u_ViewInfo.x), 1.0);
 	
 	vec4 shadowpos = u_ShadowMvp * biasPos;