From 611c95880b9e7a194352b45db79867670c55eb4f Mon Sep 17 00:00:00 2001
From: Segey Lapin <slapin@ossfans.org>
Date: Tue, 26 Oct 2021 23:03:23 +0300
Subject: [PATCH] Added terrain.gshader

---
 terrain.gdshader | 31 +++++++++++++++++++++++++++++++
 1 file changed, 31 insertions(+)
 create mode 100644 terrain.gdshader

diff --git a/terrain.gdshader b/terrain.gdshader
new file mode 100644
index 0000000..a21bbd4
--- /dev/null
+++ b/terrain.gdshader
@@ -0,0 +1,31 @@
+shader_type spatial;
+// Bitmask telling which of the 6 faces of the block are bordered by a block of lower resolution
+uniform int u_transition_mask;
+
+vec3 get_transvoxel_position(vec3 vertex_pos, vec4 vertex_col) {
+
+	int border_mask = int(vertex_col.a);
+	int cell_border_mask = border_mask & 63; // Which sides the cell is touching
+	int vertex_border_mask = (border_mask >> 6) & 63; // Which sides the vertex is touching
+
+	// If the vertex is near a side where there is a low-resolution neighbor,
+	// move it to secondary position
+	int m = u_transition_mask & (cell_border_mask & 63);
+	float t = float(m != 0);
+
+	// If the vertex lies on one or more sides, and at least one side has no low-resolution neighbor,
+	// don't move the vertex.
+	t *= float((vertex_border_mask & ~u_transition_mask) == 0);
+
+	// Position to use when border mask matches
+	vec3 secondary_position = vertex_col.rgb;
+	return mix(vertex_pos, secondary_position, t);
+}
+
+void vertex() {
+	VERTEX = get_transvoxel_position(VERTEX, COLOR);
+}
+
+void fragment() {
+	ALBEDO = vec3(1, 1, 0);
+}