Updated OpenGL LOS shader

Barotrauma/BarotraumaShared/Content/losshader_opengl.fx

@@ -6,12 +6,18 @@ Texture2D xLosTexture;
 sampler LosSampler = sampler_state { Texture = <xLosTexture>; };
 
 float4 main(float4 position : SV_Position, float4 color : COLOR0, float2 texCoord : TEXCOORD0) : COLOR0
-{	
-	float4 losColor = tex2D(LosSampler, texCoord);
-	float4 sample = tex2D(TextureSampler, texCoord);
-	
-	float4 outColor = float4(sample.x*losColor.x, sample.y*losColor.x, sample.z*losColor.x, losColor.x);
-		
+{
+	float4 sampleColor = xTexture.Sample(TextureSampler, texCoord);
+	float4 losColor = xLosTexture.Sample(LosSampler, texCoord);
+
+	float obscureAmount = 1.0f - losColor.r;
+
+	float4 outColor = float4(
+		sampleColor.r * color.r,
+		sampleColor.g * color.g,
+		sampleColor.b * color.b,
+		obscureAmount);
+
 	return outColor;
 }