EEVEE-Next: Motion Blur new implementation

The new implementation leverage compute shaders to reduce the
number of passes and complexity.

The max blur amount is now detected automatically, replacing the property
in the render panel by a simple checkbox.

The dilation algorithm has also been rewritten from scratch into a 1 pass
algorithm that does the dilation more efficiently and more precisely.

Some differences with the old implementation can be observed in areas with
complex motion.

1 files changed, 24 insertions, 0 deletions

diff --git a/source/blender/draw/intern/shaders/common_math_geom_lib.glsl b/source/blender/draw/intern/shaders/common_math_geom_lib.glsl
index ae82277d9a6..cb2da9d35bf 100644
--- a/source/blender/draw/intern/shaders/common_math_geom_lib.glsl
+++ b/source/blender/draw/intern/shaders/common_math_geom_lib.glsl
@@ -10,6 +10,11 @@ float point_plane_projection_dist(vec3 line_origin, vec3 plane_origin, vec3 plan
   return dot(plane_normal, plane_origin - line_origin);
 }
 
+float point_line_projection_dist(vec2 point, vec2 line_origin, vec2 line_normal)
+{
+  return dot(line_normal, line_origin - point);
+}
+
 float line_plane_intersect_dist(vec3 line_origin,
                                 vec3 line_direction,
                                 vec3 plane_origin,
@@ -104,6 +109,25 @@ float line_unit_box_intersect_dist_safe(vec3 line_origin, vec3 line_direction)
 }
 
 /**
+ * Same as line_unit_box_intersect_dist but for 2D case.
+ */
+float line_unit_square_intersect_dist(vec2 line_origin, vec2 line_direction)
+{
+  vec2 first_plane = (vec2(1.0) - line_origin) / line_direction;
+  vec2 second_plane = (vec2(-1.0) - line_origin) / line_direction;
+  vec2 farthest_plane = max(first_plane, second_plane);
+
+  return min_v2(farthest_plane);
+}
+
+float line_unit_square_intersect_dist_safe(vec2 line_origin, vec2 line_direction)
+{
+  vec2 safe_line_direction = max(vec2(1e-8), abs(line_direction)) *
+                             select(vec2(1.0), -vec2(1.0), lessThan(line_direction, vec2(0.0)));
+  return line_unit_square_intersect_dist(line_origin, safe_line_direction);
+}
+
+/**
  * Returns clipping distance (intersection with the nearest plane) with the given axis-aligned
  * bound box along \a line_direction.
  * Safe even if \a line_direction is degenerate.