Merge branch 'astoecke-fix-6386-water-reflection' into 'master'

Use `gl_FragCoord`  in `water_fragment.glsl` (fixes #6386)

Closes #6386

See merge request OpenMW/openmw!1347

CHANGELOG.md

@@ -73,6 +73,7 @@
     Bug #6354: SFX abruptly cut off after crossing max distance; implement soft fading of sound effects
     Bug #6363: Some scripts in Morrowland fail to work
     Bug #6376: Creatures should be able to use torches
+    Bug #6386: Artifacts in water reflection due to imprecise screen-space coordinate computation
     Feature #890: OpenMW-CS: Column filtering
     Feature #2554: Modifying an object triggers the instances table to scroll to the corresponding record
     Feature #2780: A way to see current OpenMW version in the console

files/shaders/water_fragment.glsl

@@ -132,7 +132,6 @@ vec2 normalCoords(vec2 uv, float scale, float speed, float time, float timer1, f
     return uv * (WAVE_SCALE * scale) + WIND_DIR * time * (WIND_SPEED * speed) -(previousNormal.xy/previousNormal.zz) * WAVE_CHOPPYNESS + vec2(time * timer1,time * timer2);
   }
 
-varying vec3 screenCoordsPassthrough;
 varying vec4 position;
 varying float linearDepth;
 
@@ -152,6 +151,8 @@ uniform vec3 nodePosition;
 
 uniform float rainIntensity;
 
+uniform vec2 screenRes;
+
 #define PER_PIXEL_LIGHTING 0
 
 #include "shadows_fragment.glsl"
@@ -178,8 +179,7 @@ void main(void)
 
     float shadow = unshadowedLightRatio(linearDepth);
 
-    vec2 screenCoords = screenCoordsPassthrough.xy / screenCoordsPassthrough.z;
+    vec2 screenCoords = gl_FragCoord.xy / screenRes;
-    screenCoords.y = (1.0-screenCoords.y);
 
     #define waterTimer osg_SimulationTime
 

files/shaders/water_vertex.glsl

@@ -2,7 +2,6 @@
 
 uniform mat4 projectionMatrix;
 
-varying vec3  screenCoordsPassthrough;
 varying vec4  position;
 varying float linearDepth;
 
@@ -13,14 +12,6 @@ void main(void)
 {
     gl_Position = projectionMatrix * (gl_ModelViewMatrix * gl_Vertex);
 
-    mat4 scalemat = mat4(0.5, 0.0, 0.0, 0.0,
-                         0.0, -0.5, 0.0, 0.0,
-                         0.0, 0.0, 0.5, 0.0,
-                         0.5, 0.5, 0.5, 1.0);
-
-    vec4 texcoordProj = ((scalemat) * ( gl_Position));
-    screenCoordsPassthrough = texcoordProj.xyw;
-
     position = gl_Vertex;
 
     vec4 viewPos = gl_ModelViewMatrix * gl_Vertex;