EEVEE: Port back HiZbuffer

Pretty much identical.

Texture format is now always `GPU_R32F` to remove some workarounds.

4 files changed, 68 insertions, 5 deletions

diff --git a/source/blender/draw/engines/eevee/shaders/eevee_deferred_direct_frag.glsl b/source/blender/draw/engines/eevee/shaders/eevee_deferred_direct_frag.glsl
index 9335970ba4d..dd4d0ba4f20 100644
--- a/source/blender/draw/engines/eevee/shaders/eevee_deferred_direct_frag.glsl
+++ b/source/blender/draw/engines/eevee/shaders/eevee_deferred_direct_frag.glsl
@@ -46,7 +46,7 @@ layout(std140) uniform lightprobes_info_block
   LightProbeInfoData probes_info;
 };
 
-uniform sampler2D depth_tx;
+uniform sampler2D hiz_tx;
 uniform sampler2D emission_data_tx;
 uniform sampler2D transmit_color_tx;
 uniform sampler2D transmit_normal_tx;
@@ -84,7 +84,7 @@ vec3 lightprobe_cubemap_eval(vec3 P, vec3 R, float roughness, float random_thres
 
 void main(void)
 {
-  float gbuffer_depth = texture(depth_tx, uvcoordsvar.xy).r;
+  float gbuffer_depth = texelFetch(hiz_tx, ivec2(gl_FragCoord.xy), 0).r;
   vec3 vP = get_view_space_from_depth(uvcoordsvar.xy, gbuffer_depth);
   vec3 P = point_view_to_world(vP);
   vec3 V = cameraVec(P);
diff --git a/source/blender/draw/engines/eevee/shaders/eevee_hiz_copy_frag.glsl b/source/blender/draw/engines/eevee/shaders/eevee_hiz_copy_frag.glsl
new file mode 100644
index 00000000000..f0ee9f515c9
--- /dev/null
+++ b/source/blender/draw/engines/eevee/shaders/eevee_hiz_copy_frag.glsl
@@ -0,0 +1,17 @@
+/**
+ * Copy input depth texture to lower left corner of the destination, filling any padding with
+ * clamped texture extrapolation.
+ */
+
+#pragma BLENDER_REQUIRE(common_view_lib.glsl)
+
+uniform sampler2D depth_tx;
+
+layout(location = 0) out float out_depth;
+
+void main()
+{
+  vec2 uv = gl_FragCoord.xy / vec2(textureSize(depth_tx, 0).xy);
+
+  out_depth = texture(depth_tx, uv).r;
+}
diff --git a/source/blender/draw/engines/eevee/shaders/eevee_hiz_downsample_frag.glsl b/source/blender/draw/engines/eevee/shaders/eevee_hiz_downsample_frag.glsl
new file mode 100644
index 00000000000..9a095d960b2
--- /dev/null
+++ b/source/blender/draw/engines/eevee/shaders/eevee_hiz_downsample_frag.glsl
@@ -0,0 +1,40 @@
+/**
+ * Shader that down-sample depth buffer, creating a Hierarchical-Z buffer.
+ * Saves max value of each 2x2 texel in the mipmap above the one we are rendering to.
+ * Adapted from http://rastergrid.com/blog/2010/10/hierarchical-z-map-based-occlusion-culling/
+ *
+ * Major simplification has been made since we pad the buffer to always be bigger than input to
+ * avoid mipmapping misalignement.
+ */
+
+#pragma BLENDER_REQUIRE(common_math_lib.glsl)
+
+uniform sampler2D depth_tx;
+
+uniform vec2 texel_size;
+
+layout(location = 0) out float out_depth;
+
+#ifndef GPU_ARB_texture_gather
+vec4 texGather(sampler2D tex, vec2 uv)
+{
+  vec4 ofs = vec2(0.5, 0.5, -0.5, -0.5) * texel_size.xyxy;
+  return vec4(texture(tex, uv + ofs.zw).r,
+              texture(tex, uv + ofs.zy).r,
+              texture(tex, uv + ofs.xw).r,
+              texture(tex, uv + ofs.xy).r);
+}
+#else
+#  define texGather(a, b) textureGather(a, b)
+#endif
+
+void main()
+{
+  /* NOTE(@fclem): textureSize() does not work the same on all implementations
+   * when changing the min and max texture levels. Use uniform instead (see T87801). */
+  vec2 uv = gl_FragCoord.xy * texel_size;
+
+  vec4 samp = texGather(depth_tx, uv);
+
+  out_depth = max_v4(samp);
+}
diff --git a/source/blender/draw/engines/eevee/shaders/eevee_subsurface_eval_frag.glsl b/source/blender/draw/engines/eevee/shaders/eevee_subsurface_eval_frag.glsl
index 50ec88b1990..e24c2dccdbf 100644
--- a/source/blender/draw/engines/eevee/shaders/eevee_subsurface_eval_frag.glsl
+++ b/source/blender/draw/engines/eevee/shaders/eevee_subsurface_eval_frag.glsl
@@ -23,7 +23,12 @@ layout(std140) uniform subsurface_block
   SubsurfaceData sss;
 };
 
-uniform sampler2D depth_tx;
+layout(std140) uniform hiz_block
+{
+  HiZData hiz;
+};
+
+uniform sampler2D hiz_tx;
 uniform sampler2D radiance_tx;
 uniform sampler2D transmit_color_tx;
 uniform sampler2D transmit_normal_tx;
@@ -63,7 +68,8 @@ void main(void)
 {
   vec2 center_uv = uvcoordsvar.xy;
 
-  vec3 vP = get_view_space_from_depth(center_uv, texture(depth_tx, center_uv).r);
+  float gbuffer_depth = texelFetch(hiz_tx, ivec2(gl_FragCoord.xy), 0).r;
+  vec3 vP = get_view_space_from_depth(center_uv, gbuffer_depth);
   vec4 tra_col_in = texture(transmit_color_tx, center_uv);
   vec4 tra_nor_in = texture(transmit_normal_tx, center_uv);
   vec4 tra_dat_in = texture(transmit_data_tx, center_uv);
@@ -111,7 +117,7 @@ void main(void)
     vec2 sample_uv = center_uv + sample_space * sss.samples[i].xy;
     float pdf = sss.samples[i].z;
 
-    float sample_depth = texture(depth_tx, sample_uv).r;
+    float sample_depth = texture(hiz_tx, sample_uv * hiz.uv_scale).r;
     vec3 sample_vP = get_view_space_from_depth(sample_uv, sample_depth);
 
     vec4 sample_data = texture(radiance_tx, sample_uv);