1 files changed, 42 insertions, 0 deletions

diff --git a/source/blender/draw/engines/eevee/eevee_effects.c b/source/blender/draw/engines/eevee/eevee_effects.c
index 79b4cb231a8..a4d3bc5b276 100644
--- a/source/blender/draw/engines/eevee/eevee_effects.c
+++ b/source/blender/draw/engines/eevee/eevee_effects.c
@@ -168,6 +168,11 @@ void EEVEE_effects_init(EEVEE_ViewLayerData *sldata,
     effects->enabled_effects |= EFFECT_NORMAL_BUFFER;
   }
 
+  /* Alpha checker if background is not drawn in viewport. */
+  if (!DRW_state_is_image_render() && !DRW_state_draw_background()) {
+    effects->enabled_effects |= EFFECT_ALPHA_CHECKER;
+  }
+
   /**
    * Ping Pong buffer
    */
@@ -361,6 +366,23 @@ void EEVEE_effects_cache_init(EEVEE_ViewLayerData *sldata, EEVEE_Data *vedata)
     DRW_shgroup_uniform_mat4(grp, "pastPersmat", effects->velocity_past_persmat);
     DRW_shgroup_call_add(grp, quad, NULL);
   }
+
+  if ((effects->enabled_effects & EFFECT_ALPHA_CHECKER) != 0) {
+    psl->alpha_checker = DRW_pass_create("Alpha Checker",
+                                         DRW_STATE_WRITE_COLOR | DRW_STATE_BLEND_PREMUL_UNDER);
+
+    GPUShader *checker_sh = GPU_shader_get_builtin_shader(GPU_SHADER_2D_CHECKER);
+
+    DRWShadingGroup *grp = DRW_shgroup_create(checker_sh, psl->alpha_checker);
+
+    copy_v4_fl4(effects->color_checker_dark, 0.15f, 0.15f, 0.15f, 1.0f);
+    copy_v4_fl4(effects->color_checker_light, 0.2f, 0.2f, 0.2f, 1.0f);
+
+    DRW_shgroup_uniform_vec4(grp, "color1", effects->color_checker_dark, 1);
+    DRW_shgroup_uniform_vec4(grp, "color2", effects->color_checker_light, 1);
+    DRW_shgroup_uniform_int_copy(grp, "size", 8);
+    DRW_shgroup_call_add(grp, quad, NULL);
+  }
 }
 
 #if 0 /* Not required for now */
@@ -491,6 +513,26 @@ void EEVEE_downsample_cube_buffer(EEVEE_Data *vedata, GPUTexture *texture_src, i
   DRW_stats_group_end();
 }
 
+void EEVEE_draw_alpha_checker(EEVEE_Data *vedata)
+{
+  EEVEE_PassList *psl = vedata->psl;
+  EEVEE_StorageList *stl = vedata->stl;
+  EEVEE_EffectsInfo *effects = stl->effects;
+
+  if ((effects->enabled_effects & EFFECT_ALPHA_CHECKER) != 0) {
+    float mat[4][4];
+    unit_m4(mat);
+
+    /* Fragile, rely on the fact that GPU_SHADER_2D_CHECKER
+     * only use the persmat. */
+    DRW_viewport_matrix_override_set(mat, DRW_MAT_PERS);
+
+    DRW_draw_pass(psl->alpha_checker);
+
+    DRW_viewport_matrix_override_unset(DRW_MAT_PERS);
+  }
+}
+
 void EEVEE_draw_effects(EEVEE_ViewLayerData *UNUSED(sldata), EEVEE_Data *vedata)
 {
   EEVEE_PassList *psl = vedata->psl;