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, 20 insertions, 6 deletions

diff --git a/source/blender/draw/engines/eevee_next/eevee_velocity.cc b/source/blender/draw/engines/eevee_next/eevee_velocity.cc
index 9626582983f..36734f0c28c 100644
--- a/source/blender/draw/engines/eevee_next/eevee_velocity.cc
+++ b/source/blender/draw/engines/eevee_next/eevee_velocity.cc
@@ -32,8 +32,7 @@ namespace blender::eevee {
 
 void VelocityModule::init()
 {
-  if (inst_.render && (inst_.film.enabled_passes_get() & EEVEE_RENDER_PASS_VECTOR) != 0 &&
-      true /* TODO(fclem) Motion blur */) {
+  if (inst_.render && (inst_.film.enabled_passes_get() & EEVEE_RENDER_PASS_VECTOR) != 0) {
     /* No motion blur and the vector pass was requested. Do the steps sync here. */
     const Scene *scene = inst_.scene;
     float initial_time = scene->r.cfra + scene->r.subframe;
@@ -68,10 +67,12 @@ void VelocityModule::step_camera_sync()
 {
   inst_.camera.sync();
   *camera_steps[step_] = inst_.camera.data_get();
+  step_time[step_] = inst_.scene->r.cfra + inst_.scene->r.subframe;
   /* Fix undefined camera steps when rendering is starting. */
   if ((step_ == STEP_CURRENT) && (camera_steps[STEP_PREVIOUS]->initialized == false)) {
     *camera_steps[STEP_PREVIOUS] = *static_cast<CameraData *>(camera_steps[step_]);
     camera_steps[STEP_PREVIOUS]->initialized = true;
+    step_time[STEP_PREVIOUS] = step_time[step_];
   }
 }
 
@@ -216,6 +217,7 @@ void VelocityModule::step_swap()
     SWAP(VelocityObjectBuf *, object_steps[step_a], object_steps[step_b]);
     SWAP(VelocityGeometryBuf *, geometry_steps[step_a], geometry_steps[step_b]);
     SWAP(CameraDataBuf *, camera_steps[step_a], camera_steps[step_b]);
+    SWAP(float, step_time[step_a], step_time[step_b]);
 
     for (VelocityObjectData &vel : velocity_map.values()) {
       vel.obj.ofs[step_a] = vel.obj.ofs[step_b];
@@ -242,10 +244,7 @@ void VelocityModule::step_swap()
 
 void VelocityModule::begin_sync()
 {
-  if (inst_.is_viewport()) {
-    /* Viewport always evaluate current step. */
-    step_ = STEP_CURRENT;
-  }
+  step_ = STEP_CURRENT;
   step_camera_sync();
   object_steps_usage[step_] = 0;
 }
@@ -364,6 +363,21 @@ bool VelocityModule::camera_has_motion() const
          *camera_steps[STEP_NEXT] != *camera_steps[STEP_CURRENT];
 }
 
+bool VelocityModule::camera_changed_projection() const
+{
+  /* Only valid after sync. */
+  if (inst_.is_viewport()) {
+    return camera_steps[STEP_PREVIOUS]->type != camera_steps[STEP_CURRENT]->type;
+  }
+  /* Cannot happen in render mode since we set the type during the init phase. */
+  return false;
+}
+
+float VelocityModule::step_time_delta_get(eVelocityStep start, eVelocityStep end) const
+{
+  return step_time[end] - step_time[start];
+}
+
 /** \} */
 
 }  // namespace blender::eevee