Fix T62260 edges display bug on big geometries when looked up close

1 files changed, 29 insertions, 9 deletions

diff --git a/source/blender/draw/modes/shaders/edit_mesh_overlay_geom.glsl b/source/blender/draw/modes/shaders/edit_mesh_overlay_geom.glsl
index 9a0bda3b81d..1afc7bf7b8e 100644
--- a/source/blender/draw/modes/shaders/edit_mesh_overlay_geom.glsl
+++ b/source/blender/draw/modes/shaders/edit_mesh_overlay_geom.glsl
@@ -14,13 +14,13 @@ flat out vec4 finalColorOuter_f;
 out vec4 finalColor_f;
 out float edgeCoord_f;
 
-void do_vertex(const int i, float coord, vec2 offset)
+void do_vertex(const int i, vec4 pos, float coord, vec2 offset)
 {
 	finalColor_f = (selectOveride[0] == 0) ? finalColor[i] : finalColor[0];
 	edgeCoord_f = coord;
-	gl_Position = gl_in[i].gl_Position;
+	gl_Position = pos;
 	/* Multiply offset by 2 because gl_Position range is [-1..1]. */
-	gl_Position.xy += offset * 2.0 * gl_Position.w;
+	gl_Position.xy += offset * 2.0 * pos.w;
 #ifdef USE_WORLD_CLIP_PLANES
 	world_clip_planes_set_clip_distance(gl_in[i].gl_ClipDistance);
 #endif
@@ -30,8 +30,28 @@ void do_vertex(const int i, float coord, vec2 offset)
 void main()
 {
 	vec2 ss_pos[2];
-	ss_pos[0] = gl_in[0].gl_Position.xy / gl_in[0].gl_Position.w;
-	ss_pos[1] = gl_in[1].gl_Position.xy / gl_in[1].gl_Position.w;
+
+	/* Clip line against near plane to avoid deformed lines. */
+	vec4 pos0 = gl_in[0].gl_Position;
+	vec4 pos1 = gl_in[1].gl_Position;
+	vec2 pz_ndc = vec2(pos0.z / pos0.w, pos1.z / pos1.w);
+	bvec2 clipped = lessThan(pz_ndc, vec2(-1.0));
+	if (all(clipped)) {
+		/* Totally clipped. */
+		return;
+	}
+
+	vec4 pos01 = pos0 - pos1;
+	float ofs = abs((pz_ndc.y + 1.0) / (pz_ndc.x - pz_ndc.y));
+	if (clipped.y) {
+		pos1 += pos01 * ofs;
+	}
+	else if (clipped.x) {
+		pos0 -= pos01 * (1.0 - ofs);
+	}
+
+	ss_pos[0] = pos0.xy / pos0.w;
+	ss_pos[1] = pos1.xy / pos1.w;
 
 	vec2 line = ss_pos[0] - ss_pos[1];
 	line = abs(line) * viewportSize;
@@ -51,10 +71,10 @@ void main()
 	bool horizontal = line.x > line.y;
 	edge_ofs = (horizontal) ? edge_ofs.zyz : edge_ofs.xzz;
 
-	do_vertex(0,  half_size,  edge_ofs.xy);
-	do_vertex(0, -half_size, -edge_ofs.xy);
-	do_vertex(1,  half_size,  edge_ofs.xy);
-	do_vertex(1, -half_size, -edge_ofs.xy);
+	do_vertex(0, pos0,  half_size,  edge_ofs.xy);
+	do_vertex(0, pos0, -half_size, -edge_ofs.xy);
+	do_vertex(1, pos1,  half_size,  edge_ofs.xy);
+	do_vertex(1, pos1, -half_size, -edge_ofs.xy);
 
 	EndPrimitive();
 }