EEVEE: Fix smooth transition when using render borders

The first sample buffer is fullscreen and needs to have its uvs
corrected to match the render border viewport.

2 files changed, 8 insertions, 3 deletions

diff --git a/source/blender/draw/engines/eevee/eevee_film.cc b/source/blender/draw/engines/eevee/eevee_film.cc
index 143c795f10f..a45d503a25c 100644
--- a/source/blender/draw/engines/eevee/eevee_film.cc
+++ b/source/blender/draw/engines/eevee/eevee_film.cc
@@ -166,8 +166,10 @@ void Film::end_sync()
   if (do_smooth_viewport_smooth_transition() && (data_.opacity < 1.0f || is_first_sample)) {
     char full_name[32];
     SNPRINTF(full_name, "Film.%s.first_sample", name_.c_str());
-    eGPUTextureFormat tex_format = GPU_texture_format(DRW_viewport_texture_list_get()->color);
-    first_sample_tx_.ensure(full_name, UNPACK2(data_.extent), 1, tex_format);
+    GPUTexture *dtxl_color = DRW_viewport_texture_list_get()->color;
+    eGPUTextureFormat tex_format = GPU_texture_format(dtxl_color);
+    int extent[2] = {GPU_texture_width(dtxl_color), GPU_texture_height(dtxl_color)};
+    first_sample_tx_.ensure(full_name, UNPACK2(extent), 1, tex_format);
     first_sample_ref_ = first_sample_tx_;
   }
   else {
diff --git a/source/blender/draw/engines/eevee/shaders/eevee_film_resolve_frag.glsl b/source/blender/draw/engines/eevee/shaders/eevee_film_resolve_frag.glsl
index 8b77649481e..bdf36d52e96 100644
--- a/source/blender/draw/engines/eevee/shaders/eevee_film_resolve_frag.glsl
+++ b/source/blender/draw/engines/eevee/shaders/eevee_film_resolve_frag.glsl
@@ -23,6 +23,9 @@ void main(void)
 
   out_color = film_data_decode(film, color, weight);
 
-  vec4 first_sample = textureLod(first_sample_tx, uv, 0.0);
+  /* First sample is stored in a fullscreen buffer. */
+  vec2 uv_first_sample = ((uv * film.extent) + film.offset) /
+                         vec2(textureSize(first_sample_tx, 0).xy);
+  vec4 first_sample = textureLod(first_sample_tx, uv_first_sample, 0.0);
   out_color = mix(first_sample, out_color, film.opacity);
 }