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, 26 insertions, 13 deletions

diff --git a/source/blender/draw/engines/eevee_next/shaders/eevee_velocity_lib.glsl b/source/blender/draw/engines/eevee_next/shaders/eevee_velocity_lib.glsl
index 3a958712885..c0a5b976810 100644
--- a/source/blender/draw/engines/eevee_next/shaders/eevee_velocity_lib.glsl
+++ b/source/blender/draw/engines/eevee_next/shaders/eevee_velocity_lib.glsl
@@ -2,8 +2,6 @@
 #pragma BLENDER_REQUIRE(common_view_lib.glsl)
 #pragma BLENDER_REQUIRE(eevee_camera_lib.glsl)
 
-#ifdef VELOCITY_CAMERA
-
 vec4 velocity_pack(vec4 data)
 {
   return data * 0.01;
@@ -14,6 +12,8 @@ vec4 velocity_unpack(vec4 data)
   return data * 100.0;
 }
 
+#ifdef VELOCITY_CAMERA
+
 /**
  * Given a triple of position, compute the previous and next motion vectors.
  * Returns uv space motion vectors in pairs (motion_prev.xy, motion_next.xy).
@@ -24,7 +24,15 @@ vec4 velocity_surface(vec3 P_prv, vec3 P, vec3 P_nxt)
   vec2 prev_uv = project_point(camera_prev.persmat, P_prv).xy;
   vec2 curr_uv = project_point(camera_curr.persmat, P).xy;
   vec2 next_uv = project_point(camera_next.persmat, P_nxt).xy;
-
+  /* Fix issue with perspective division. */
+  if (any(isnan(prev_uv))) {
+    prev_uv = curr_uv;
+  }
+  if (any(isnan(next_uv))) {
+    next_uv = curr_uv;
+  }
+  /* NOTE: We output both vectors in the same direction so we can reuse the same vector
+   * with rgrg swizzle in viewport. */
   vec4 motion = vec4(prev_uv - curr_uv, curr_uv - next_uv);
   /* Convert NDC velocity to UV velocity */
   motion *= 0.5;
@@ -45,7 +53,8 @@ vec4 velocity_background(vec3 vV)
   vec2 prev_uv = project_point(camera_prev.winmat, V).xy;
   vec2 curr_uv = project_point(camera_curr.winmat, V).xy;
   vec2 next_uv = project_point(camera_next.winmat, V).xy;
-
+  /* NOTE: We output both vectors in the same direction so we can reuse the same vector
+   * with rgrg swizzle in viewport. */
   vec4 motion = vec4(prev_uv - curr_uv, curr_uv - next_uv);
   /* Convert NDC velocity to UV velocity */
   motion *= 0.5;
@@ -53,16 +62,8 @@ vec4 velocity_background(vec3 vV)
   return motion;
 }
 
-/**
- * Load and resolve correct velocity as some pixels might still not have correct
- * motion data for performance reasons.
- * Returns motion vector in render UV space.
- */
-vec4 velocity_resolve(sampler2D vector_tx, ivec2 texel, float depth)
+vec4 velocity_resolve(vec4 vector, vec2 uv, float depth)
 {
-  vec2 uv = (vec2(texel) + 0.5) / vec2(textureSize(vector_tx, 0).xy);
-  vec4 vector = texelFetch(vector_tx, texel, 0);
-
   if (vector.x == VELOCITY_INVALID) {
     bool is_background = (depth == 1.0);
     if (is_background) {
@@ -79,6 +80,18 @@ vec4 velocity_resolve(sampler2D vector_tx, ivec2 texel, float depth)
   return velocity_unpack(vector);
 }
 
+/**
+ * Load and resolve correct velocity as some pixels might still not have correct
+ * motion data for performance reasons.
+ * Returns motion vector in render UV space.
+ */
+vec4 velocity_resolve(sampler2D vector_tx, ivec2 texel, float depth)
+{
+  vec2 uv = (vec2(texel) + 0.5) / vec2(textureSize(vector_tx, 0).xy);
+  vec4 vector = texelFetch(vector_tx, texel, 0);
+  return velocity_resolve(vector, uv, depth);
+}
+
 #endif
 
 #ifdef MAT_VELOCITY