Overlay: Wireframe: New method to avoid zfighting with geometry

This new method is only enabled if Overlay Smooth Wire is enabled.

This method gives really nice results but has some downside:
- Require a depth copy or loose the ability to write wire depth to the
  depth buffer and have correct depth ordering of wires. This patch use the former, with its associated cost.
- Require some depth sampling and prevent early depth test (i.e: has
  some performance impact).
- Has some relatively minor instability with geometry that are perpendicular
  to the view and intersecting with other geometry.

Pros:
- Compared to a fullpass approach this is surely going to have less
  performance impact and much higher quality.
- Removes the additional vertex offset. (see T74961)
- Fixes all half edges z-fighting.

{F8428014}

{F8428015}

Reviewed By: brecht

Differential Revision: https://developer.blender.org/D7233

1 files changed, 4 insertions, 1 deletions

diff --git a/source/blender/draw/engines/overlay/overlay_private.h b/source/blender/draw/engines/overlay/overlay_private.h
index 7cc83c76857..bd9583c6a5f 100644
--- a/source/blender/draw/engines/overlay/overlay_private.h
+++ b/source/blender/draw/engines/overlay/overlay_private.h
@@ -293,6 +293,8 @@ typedef struct OVERLAY_PrivateData {
 
   struct {
     bool enabled;
+    bool do_depth_copy;
+    bool do_depth_infront_copy;
   } antialiasing;
   struct {
     bool show_handles;
@@ -411,6 +413,7 @@ void OVERLAY_antialiasing_start(OVERLAY_Data *vedata);
 void OVERLAY_antialiasing_end(OVERLAY_Data *vedata);
 void OVERLAY_xray_fade_draw(OVERLAY_Data *vedata);
 void OVERLAY_xray_depth_copy(OVERLAY_Data *vedata);
+void OVERLAY_xray_depth_infront_copy(OVERLAY_Data *vedata);
 
 bool OVERLAY_armature_is_pose_mode(Object *ob, const struct DRWContextState *draw_ctx);
 void OVERLAY_armature_cache_init(OVERLAY_Data *vedata);
@@ -613,7 +616,7 @@ GPUShader *OVERLAY_shader_particle_shape(void);
 GPUShader *OVERLAY_shader_pointcloud_dot(void);
 GPUShader *OVERLAY_shader_sculpt_mask(void);
 GPUShader *OVERLAY_shader_volume_velocity(bool use_needle);
-GPUShader *OVERLAY_shader_wireframe(void);
+GPUShader *OVERLAY_shader_wireframe(bool custom_bias);
 GPUShader *OVERLAY_shader_wireframe_select(void);
 GPUShader *OVERLAY_shader_xray_fade(void);