Eevee: Implement Wireframe Node

This implementation is a bit hacky but match cycles pretty close.

If pixel size is not enabled, it will use the geom shader to
compute distances between vertices. This will have a cost.

Implementation is a bit hacky in gpu_codegen to make the geom shader works
in an optional manner.

1 files changed, 24 insertions, 1 deletions

diff --git a/source/blender/gpu/shaders/gpu_shader_material.glsl b/source/blender/gpu/shaders/gpu_shader_material.glsl
index 84e4165ac00..8fa1828bd9c 100644
--- a/source/blender/gpu/shaders/gpu_shader_material.glsl
+++ b/source/blender/gpu/shaders/gpu_shader_material.glsl
@@ -1,10 +1,10 @@
 
-uniform mat4 ModelMatrix;
 uniform mat4 ModelViewMatrix;
 uniform mat4 ModelViewMatrixInverse;
 uniform mat3 NormalMatrix;
 
 #ifndef ATTRIB
+uniform mat4 ModelMatrix;
 uniform mat4 ModelMatrixInverse;
 #endif
 
@@ -1423,6 +1423,29 @@ void node_emission(vec4 color, float strength, vec3 vN, out Closure result)
 #endif
 }
 
+void node_wireframe(float size, vec2 barycentric, vec3 barycentric_dist, out float fac)
+{
+	vec3 barys = barycentric.xyy;
+	barys.z = 1.0 - barycentric.x - barycentric.y;
+
+	size *= 0.5;
+	vec3 s = step(-size, -barys * barycentric_dist);
+
+	fac = max(s.x, max(s.y, s.z));
+}
+
+void node_wireframe_screenspace(float size, vec2 barycentric, out float fac)
+{
+	vec3 barys = barycentric.xyy;
+	barys.z = 1.0 - barycentric.x - barycentric.y;
+
+	size *= (1.0 / 3.0);
+	vec3 deltas = fwidth(barys);
+	vec3 s = step(-deltas * size, -barys);
+
+	fac = max(s.x, max(s.y, s.z));
+}
+
 /* background */
 
 void background_transform_to_world(vec3 viewvec, out vec3 worldvec)