Adds resolve PBR compute shader

Also fixes sky shader as it was writing negative values for -Y
direction.

binaries/data/mods/mod/shaders/effects/compute_resolve_pbr.xml

@@ -0,0 +1,8 @@
+<?xml version="1.0" encoding="utf-8"?>
+<effect>
+	<technique>
+		<require shaders="glsl"/>
+		<require shaders="spirv"/>
+		<compute shader="compute_resolve_pbr"/>
+	</technique>
+</effect>

binaries/data/mods/mod/shaders/glsl/compute_resolve_pbr.cs

@@ -0,0 +1,34 @@
+#version 430
+
+#include "common/compute.h"
+
+BEGIN_DRAW_TEXTURES
+	TEXTURE_2D(0, inTex)
+END_DRAW_TEXTURES
+
+BEGIN_DRAW_UNIFORMS
+	UNIFORM(vec4, screenSize)
+	// Premultiplied exposure, already contains 2^exposure.
+	UNIFORM(float, exposure)
+END_DRAW_UNIFORMS
+
+STORAGE_2D(0, rgba8, outTex);
+
+vec3 applyTonemapper(vec3 color)
+{
+	float whitePoint = 10.0;
+	// Extendend Reinhard:
+	// https://www-old.cs.utah.edu/docs/techreports/2002/pdf/UUCS-02-001.pdf
+	return color * (vec3(1.0) + color / (whitePoint * whitePoint)) / (vec3(1.0) + color);
+}
+
+layout(local_size_x = 8, local_size_y = 8, local_size_z = 1) in;
+void main()
+{
+	ivec2 position = ivec2(gl_GlobalInvocationID.xy);
+	if (any(greaterThanEqual(position, ivec2(screenSize.xy))))
+		return;
+	vec3 hdrColor = texelFetch(GET_DRAW_TEXTURE_2D(inTex), position, 0).rgb;
+	vec3 sdrColor = applyTonemapper(hdrColor * exposure);
+	imageStore(outTex, position, vec4(sdrColor, 1.0));
+}

binaries/data/mods/mod/shaders/glsl/compute_resolve_pbr.xml

@@ -0,0 +1,4 @@
+<?xml version="1.0" encoding="utf-8"?>
+<program type="glsl">
+	<compute file="glsl/compute_resolve_pbr.cs"/>
+</program>

binaries/data/mods/mod/shaders/glsl/sky.fs

@@ -6,10 +6,10 @@
 
 void main()
 {
-    vec4 tex = SAMPLE_CUBE(GET_DRAW_TEXTURE_CUBE(baseTex), v_tex);
+    vec3 color = SAMPLE_CUBE(GET_DRAW_TEXTURE_CUBE(baseTex), v_tex).rgb;
 
     float m = (1.0 - v_tex.y) - 0.75;
     m *= 4.0;
 
-    OUTPUT_FRAGMENT_SINGLE_COLOR((v_tex.y > 0.0) ? (tex * m) : tex);
+    OUTPUT_FRAGMENT_SINGLE_COLOR(vec4((v_tex.y > 0.0) ? clamp(color * m, 0.0, 1.0) : color, 1.0));
 }