Merge branch 'main' into retopology-overlay

The bias property is now called offset, not just in the UI but everywhere, because I like consistency.
get_homogenous_z_offset no longer negates its output, and has some more documentation.
The offset property is now of distance type, because it is a viewspace offset.
To make this more clear the soft max is increased to 10.
Because there's no point in arbitrarily limiting the values users can input, the hard max is FLT_MAX now.
I kept step the same, because it good the way it is.

@@ -9,5 +9,8 @@ void main()
   vec3 world_pos = point_object_to_world(pos);
   gl_Position = point_world_to_ndc(world_pos);
 
+  /* Offset Z position for retopology overlay. */

@@ -10,2 +10,4 @@
   gl_Position = point_world_to_ndc(world_pos);
 
+  /* Offset Z position for retopology overlay. */
+  gl_Position.z -= max(0.0, retopologyBias) / abs(gl_Position.w);

@@ -96,2 +96,4 @@
 #endif
 
+  /* Offset Z position for retopology overlay. */
+  gl_Position.z -= max(0.0, retopologyBias) / abs(gl_Position.w);

@@ -0,0 +1,13 @@
+

@@ -102,2 +106,3 @@
     /* Complementary Depth Pass */
-    state = DRW_STATE_WRITE_DEPTH | DRW_STATE_DEPTH_LESS_EQUAL | DRW_STATE_CULL_BACK;
+    state = DRW_STATE_WRITE_DEPTH | DRW_STATE_DEPTH_LESS_EQUAL |
+            ((show_retopology) ? DRWState(0) : DRW_STATE_CULL_BACK);

@@ -149,3 +156,3 @@
       DRWShadingGroup **shgrp = (j == 0) ? &pd->edit_mesh_faces_grp[i] :
                                            &pd->edit_mesh_faces_cage_grp[i];
-      state = state_common;
+      state = state_common | ((show_retopology) ? DRW_STATE_CULL_BACK : DRWState(0));

@@ -258,2 +258,4 @@
 }
 
+/* From "Projection Matrix Tricks" by Eric Lengyel:
+ * http://www.terathon.com/gdc07_lengyel.pdf (p. 18 Depth Modification)

@@ -260,0 +262,4 @@
+ *
+ * View Z is used to adjust for perspective projection.
+ * Homogenous W is used to convert from NDC to homogenous space. */
+float get_homogenous_z_offset(float vs_z, float hs_w, float offset)

@@ -260,0 +265,4 @@
+float get_homogenous_z_offset(float vs_z, float hs_w, float offset)
+{
+  if (ProjectionMatrix[3][3] == 0.0) {
+    return -ProjectionMatrix[3][2] * (offset / (vs_z * (vs_z + offset))) * hs_w;

@@ -4533,2 +4532,4 @@
+  RNA_def_property_ui_text(prop, "Retopology", "Use retopology display");
   RNA_def_property_update(prop, NC_SPACE | ND_SPACE_VIEW3D | NS_VIEW3D_SHADING, NULL);
 
+  prop = RNA_def_property(srna, "retopology_bias", PROP_FLOAT, PROP_FACTOR);

@@ -4534,1 +4534,4 @@
 
+  prop = RNA_def_property(srna, "retopology_bias", PROP_FLOAT, PROP_FACTOR);
+  RNA_def_property_float_sdna(prop, NULL, "overlay.retopology_bias");
+  RNA_def_property_ui_text(prop, "Retopology Bias", "Z Bias used to draw edit mesh in front");

@@ -4535,0 +4535,4 @@
+  prop = RNA_def_property(srna, "retopology_bias", PROP_FLOAT, PROP_FACTOR);
+  RNA_def_property_float_sdna(prop, NULL, "overlay.retopology_bias");
+  RNA_def_property_ui_text(prop, "Retopology Bias", "Z Bias used to draw edit mesh in front");
+  RNA_def_property_range(prop, 0.0f, 100000.0f);

@@ -65,0 +64,4 @@
+  RegionView3D *rv3d = draw_ctx->rv3d;
+  bool show_retopology = (v3d->overlay.edit_flag & V3D_OVERLAY_EDIT_RETOPOLOGY) != 0;
+  /* Add epsilon to ensure the value is never zero when the effect is enabled. */
+  float retopology_offset = (show_retopology) ? (v3d->overlay.retopology_offset + FLT_EPSILON) :