Added a heuristic component to the temporal filter to reduce its smea…

…ring of specular reflections.

With the new materials and BRDF, specular channel often becomes more pronounced, and the temporal filter blurs it by redistributing the energy between the bilinear taps from the previous frame. Shortening the effective history when the surfaces are moving helps reduce that effect.

src/refresh/vkpt/shader/asvgf_temporal.comp

@@ -151,6 +151,8 @@ main()
 		pos_prev = ((vec2(ipos) + vec2(0.5)) * vec2(global_ubo.inv_width * 2, global_ubo.inv_height) + motion.xy) * vec2(global_ubo.prev_width / 2, global_ubo.prev_height);
 	}
 
+	float motion_length = length(motion.xy * vec2(global_ubo.width, global_ubo.height));
+
 	// Load the parameters of the target pixel
 	float depth_curr;
 	vec3 normal_curr;
@@ -342,7 +344,8 @@ main()
 	if(temporal_sample_valid_spec)
 	{
 		// Same sequence as above, only for the specular channel
-		float antilag_alpha_spec = clamp(mix(1.0, global_ubo.flt_antilag_spec * grad_hf_spec.y, global_ubo.flt_temporal_spec), 0, 1);
+		float antilag = grad_hf_spec.y * global_ubo.flt_antilag_spec + motion_length * global_ubo.flt_antilag_spec_motion;
+		float antilag_alpha_spec = clamp(mix(1.0, antilag, global_ubo.flt_temporal_spec), 0, 1);
 		float hist_len_spec = min(temporal_color_histlen_spec.a * pow(1.0 - antilag_alpha_spec, 10) + 1.0, 256.0);
 		float alpha_color_spec = max(global_ubo.flt_min_alpha_color_spec, 1.0 / hist_len_spec);
 		alpha_color_spec = mix(alpha_color_spec, 1.0, antilag_alpha_spec);

src/refresh/vkpt/shader/global_ubo.h

@@ -37,6 +37,7 @@ with this program; if not, write to the Free Software Foundation, Inc.,
 	UBO_CVAR_DO(flt_antilag_hf, 1) /* A-SVGF anti-lag filter strength, [0..inf) */ \
 	UBO_CVAR_DO(flt_antilag_lf, 0.2) \
 	UBO_CVAR_DO(flt_antilag_spec, 2) \
+	UBO_CVAR_DO(flt_antilag_spec_motion, 0.004) /* scaler for motion vector scaled specular anti-blur adjustment */ \
 	UBO_CVAR_DO(flt_atrous_depth, 0.5) /* wavelet fitler sensitivity to depth, [0..inf) */ \
 	UBO_CVAR_DO(flt_atrous_deflicker_lf, 2) /* max brightness difference between adjacent pixels in the LF channel, (0..inf) */ \
 	UBO_CVAR_DO(flt_atrous_hf, 4) /* number of a-trous wavelet filter iterations on the LF channel, [0..4] */ \