Eevee: Small code codestyle and fixes.

Rename get_specular_dominant_dir to get_specular_reflection_dominant_dir.
Add Zero length N check everywhere.

source/blender/draw/engines/eevee/shaders/bsdf_common_lib.glsl

@@ -281,7 +281,7 @@ vec3 get_world_space_from_depth(vec2 uvcoords, float depth)
 	return (ViewMatrixInverse * vec4(get_view_space_from_depth(uvcoords, depth), 1.0)).xyz;
 }
 
-vec3 get_specular_dominant_dir(vec3 N, vec3 V, float roughness)
+vec3 get_specular_reflection_dominant_dir(vec3 N, vec3 V, float roughness)
 {
 	vec3 R = -reflect(V, N);
 	float smoothness = 1.0 - roughness;
@@ -334,7 +334,7 @@ vec3 F_area(vec3 f0, vec2 lut)
 	return saturate(50.0 * dot(f0, vec3(0.3, 0.6, 0.1))) * fac.y + fac.x * f0;
 }
 
-/* Fresnel approximation for LTC area lights (not MRP) */
+/* Fresnel approximation for IBL */
 vec3 F_ibl(vec3 f0, vec2 lut)
 {
 	/* Unreal specular matching : if specular color is below 2% intensity,

source/blender/draw/engines/eevee/shaders/bsdf_direct_lib.glsl

@@ -105,7 +105,7 @@ vec3 direct_ggx_sun(LightData ld, vec3 N, vec3 V, float roughness, vec3 f0)
 vec3 direct_ggx_sphere(LightData ld, vec3 N, vec3 V, vec4 l_vector, float roughness, vec3 f0)
 {
 	vec3 L = l_vector.xyz / l_vector.w;
-	vec3 spec_dir = get_specular_dominant_dir(N, V, roughness);
+	vec3 spec_dir = get_specular_reflection_dominant_dir(N, V, roughness);
 	vec3 P = line_aligned_plane_intersect(vec3(0.0), spec_dir, l_vector.xyz);
 
 	vec3 Px = normalize(P - l_vector.xyz) * ld.l_radius;

source/blender/draw/engines/eevee/shaders/bsdf_sampling_lib.glsl

@@ -6,12 +6,16 @@ uniform float invSampleCount;
 
 vec2 jitternoise = vec2(0.0);
 
-#ifdef NOISE_SIZE
+#ifndef UTIL_TEX
+#define UTIL_TEX
+uniform sampler2DArray utilTex;
+#endif /* UTIL_TEX */
+
 void setup_noise(void)
 {
-	jitternoise = texture(texJitter, gl_FragCoord.xy / NOISE_SIZE).rg; /* Global variable */
+	jitternoise = texture(utilTex, vec3(gl_FragCoord.xy / LUT_SIZE, 2.0)).rg; /* Global variable */
+	jitternoise.g = (jitternoise.g - 0.5) * 2.0;
 }
-#endif
 
 #ifdef HAMMERSLEY_SIZE
 vec3 hammersley_3d(float i, float invsamplenbr)

source/blender/draw/engines/eevee/shaders/effect_ssr_frag.glsl

@@ -191,7 +191,7 @@ out vec4 fragColor;
 void fallback_cubemap(vec3 N, vec3 V, vec3 W, float roughness, float roughnessSquared, inout vec4 spec_accum)
 {
 	/* Specular probes */
-	vec3 spec_dir = get_specular_dominant_dir(N, V, roughnessSquared);
+	vec3 spec_dir = get_specular_reflection_dominant_dir(N, V, roughnessSquared);
 
 	/* Starts at 1 because 0 is world probe */
 	for (int i = 1; i < MAX_PROBE && i < probe_count && spec_accum.a < 0.999; ++i) {

source/blender/draw/engines/eevee/shaders/lightprobe_lib.glsl

@@ -167,8 +167,7 @@ vec3 probe_evaluate_world_spec(vec3 R, float roughness)
 
 vec3 probe_evaluate_planar(
         float id, PlanarData pd, vec3 W, vec3 N, vec3 V,
-        float rand, float roughness,
-        inout float fade)
+        float roughness, inout float fade)
 {
 	/* Find view vector / reflection plane intersection. */
 	vec3 point_on_plane = line_plane_intersect(W, V, pd.pl_plane_eq);

source/blender/draw/engines/eevee/shaders/lit_surface_frag.glsl

@@ -45,8 +45,6 @@ vec3 eevee_surface_lit(vec3 N, vec3 albedo, vec3 f0, float roughness, float ao,
 
 	vec3 V = cameraVec;
 
-	vec4 rand = texture(utilTex, vec3(gl_FragCoord.xy / LUT_SIZE, 2.0));
-
 	/* ---------------- SCENE LAMPS LIGHTING ----------------- */
 
 #ifdef HAIR_SHADER
@@ -99,13 +97,13 @@ vec3 eevee_surface_lit(vec3 N, vec3 albedo, vec3 f0, float roughness, float ao,
 			float fade = probe_attenuation_planar(pd, worldPosition, N, roughness);
 
 			if (fade > 0.0) {
-				vec3 spec = probe_evaluate_planar(float(i), pd, worldPosition, N, V, rand.r, roughness, fade);
+				vec3 spec = probe_evaluate_planar(float(i), pd, worldPosition, N, V, roughness, fade);
 				accumulate_light(spec, fade, spec_accum);
 			}
 		}
 
 		/* Specular probes */
-		vec3 spec_dir = get_specular_dominant_dir(N, V, roughnessSquared);
+		vec3 spec_dir = get_specular_reflection_dominant_dir(N, V, roughnessSquared);
 
 		/* Starts at 1 because 0 is world probe */
 		for (int i = 1; i < MAX_PROBE && i < probe_count && spec_accum.a < 0.999; ++i) {
@@ -126,6 +124,8 @@ vec3 eevee_surface_lit(vec3 N, vec3 albedo, vec3 f0, float roughness, float ao,
 		}
 	}
 
+	vec4 rand = texture(utilTex, vec3(gl_FragCoord.xy / LUT_SIZE, 2.0));
+
 	/* Ambient Occlusion */
 	vec3 bent_normal;
 	float final_ao = occlusion_compute(N, viewPosition, ao, rand.rg, bent_normal);
@@ -178,11 +178,27 @@ vec3 eevee_surface_clearcoat_lit(
 	C_roughness = clamp(C_roughness, 1e-8, 0.9999);
 	float C_roughnessSquared = C_roughness * C_roughness;
 
-	vec3 V = cameraVec;
+	/* Zero length vectors cause issues, see: T51979. */
+#if 0
 	N = normalize(N);
 	C_N = normalize(C_N);
+#else
+	{
+		float len = length(N);
+		if (isnan(len)) {
+			return vec3(0.0);
+		}
+		N /= len;
 
-	vec4 rand = texture(utilTex, vec3(gl_FragCoord.xy / LUT_SIZE, 2.0));
+		len = length(C_N);
+		if (isnan(len)) {
+			return vec3(0.0);
+		}
+		C_N /= len;
+	}
+#endif
+
+	vec3 V = cameraVec;
 
 	/* ---------------- SCENE LAMPS LIGHTING ----------------- */
 
@@ -239,18 +255,18 @@ vec3 eevee_surface_clearcoat_lit(
 
 		if (fade > 0.0) {
 			if (!(ssrToggle && ssr_id == outputSsrId)) {
-				vec3 spec = probe_evaluate_planar(float(i), pd, worldPosition, N, V, rand.r, roughness, fade);
+				vec3 spec = probe_evaluate_planar(float(i), pd, worldPosition, N, V, roughness, fade);
 				accumulate_light(spec, fade, spec_accum);
 			}
 
-			vec3 C_spec = probe_evaluate_planar(float(i), pd, worldPosition, C_N, V, rand.r, C_roughness, fade);
+			vec3 C_spec = probe_evaluate_planar(float(i), pd, worldPosition, C_N, V, C_roughness, fade);
 			accumulate_light(C_spec, fade, C_spec_accum);
 		}
 	}
 
 	/* Specular probes */
-	vec3 spec_dir = get_specular_dominant_dir(N, V, roughnessSquared);
-	vec3 C_spec_dir = get_specular_dominant_dir(C_N, V, C_roughnessSquared);
+	vec3 spec_dir = get_specular_reflection_dominant_dir(N, V, roughnessSquared);
+	vec3 C_spec_dir = get_specular_reflection_dominant_dir(C_N, V, C_roughnessSquared);
 
 	/* Starts at 1 because 0 is world probe */
 	for (int i = 1; i < MAX_PROBE && i < probe_count && spec_accum.a < 0.999; ++i) {
@@ -280,6 +296,8 @@ vec3 eevee_surface_clearcoat_lit(
 		accumulate_light(C_spec, 1.0, C_spec_accum);
 	}
 
+	vec4 rand = texture(utilTex, vec3(gl_FragCoord.xy / LUT_SIZE, 2.0));
+
 	/* Ambient Occlusion */
 	vec3 bent_normal;
 	float final_ao = occlusion_compute(N, viewPosition, ao, rand.rg, bent_normal);
@@ -330,9 +348,19 @@ vec3 eevee_surface_clearcoat_lit(
 vec3 eevee_surface_diffuse_lit(vec3 N, vec3 albedo, float ao)
 {
 	vec3 V = cameraVec;
-	N = normalize(N);
 
-	vec4 rand = texture(utilTex, vec3(gl_FragCoord.xy / LUT_SIZE, 2.0));
+	/* Zero length vectors cause issues, see: T51979. */
+#if 0
+	N = normalize(N);
+#else
+	{
+		float len = length(N);
+		if (isnan(len)) {
+			return vec3(0.0);
+		}
+		N /= len;
+	}
+#endif
 
 	/* ---------------- SCENE LAMPS LIGHTING ----------------- */
 
@@ -371,6 +399,8 @@ vec3 eevee_surface_diffuse_lit(vec3 N, vec3 albedo, float ao)
 
 	/* ---------------- DIFFUSE ENVIRONMENT LIGHTING ----------------- */
 
+	vec4 rand = texture(utilTex, vec3(gl_FragCoord.xy / LUT_SIZE, 2.0));
+
 	/* Ambient Occlusion */
 	vec3 bent_normal;
 	float final_ao = occlusion_compute(N, viewPosition, ao, rand.rg, bent_normal);
@@ -410,9 +440,19 @@ vec3 eevee_surface_glossy_lit(vec3 N, vec3 f0, float roughness, float ao, int ss
 	float roughnessSquared = roughness * roughness;
 
 	vec3 V = cameraVec;
-	N = normalize(N);
 
-	vec4 rand = texture(utilTex, vec3(gl_FragCoord.xy / LUT_SIZE, 2.0));
+	/* Zero length vectors cause issues, see: T51979. */
+#if 0
+	N = normalize(N);
+#else
+	{
+		float len = length(N);
+		if (isnan(len)) {
+			return vec3(0.0);
+		}
+		N /= len;
+	}
+#endif
 
 	/* ---------------- SCENE LAMPS LIGHTING ----------------- */
 
@@ -462,13 +502,13 @@ vec3 eevee_surface_glossy_lit(vec3 N, vec3 f0, float roughness, float ao, int ss
 			float fade = probe_attenuation_planar(pd, worldPosition, N, roughness);
 
 			if (fade > 0.0) {
-				vec3 spec = probe_evaluate_planar(float(i), pd, worldPosition, N, V, rand.r, roughness, fade);
+				vec3 spec = probe_evaluate_planar(float(i), pd, worldPosition, N, V, roughness, fade);
 				accumulate_light(spec, fade, spec_accum);
 			}
 		}
 
 		/* Specular probes */
-		vec3 spec_dir = get_specular_dominant_dir(N, V, roughnessSquared);
+		vec3 spec_dir = get_specular_reflection_dominant_dir(N, V, roughnessSquared);
 
 		/* Starts at 1 because 0 is world probe */
 		for (int i = 1; i < MAX_PROBE && i < probe_count && spec_accum.a < 0.999; ++i) {
@@ -489,6 +529,8 @@ vec3 eevee_surface_glossy_lit(vec3 N, vec3 f0, float roughness, float ao, int ss
 		}
 	}
 
+	vec4 rand = texture(utilTex, vec3(gl_FragCoord.xy / LUT_SIZE, 2.0));
+
 	/* Ambient Occlusion */
 	vec3 bent_normal;
 	float final_ao = occlusion_compute(N, viewPosition, ao, rand.rg, bent_normal);