Grass interaction (Tutorial Part 3)

grass.gd

@@ -0,0 +1,7 @@
+@tool
+extends MultiMeshInstance3D
+
+
+func _process(delta: float) -> void:
+	if has_node("MeshInstance3D"):
+		material_override.set_shader_parameter("object_position", $MeshInstance3D.position)

grass.gd.uid

@@ -0,0 +1 @@
+uid://bmx385ngdvuwt

grass.gdshader

@@ -13,11 +13,56 @@ uniform sampler2D patch_noise;
 uniform float patch_scale = 5.0;
 varying float patch_factor;
 
+uniform sampler2D wind_noise;
+uniform float wind_strength = 0.1;
+uniform vec2 wind_direction = vec2(1.0, 0.0);
+uniform float wind_bend_strength = 2.0;
+uniform float wind_ao_affect = 1.5;
+
+uniform float object_radius = 1.0;
+uniform vec3 object_position;
+
 varying float bottom_to_top;
+varying float current_wind_bend;
+varying float cut_height;
 
 void vertex() {
+	cut_height = 1.0;
+
+	// Cutting all grass on the right
+	if (NODE_POSITION_WORLD.x > 0.0) {
+		cut_height = 0.5;
+
+		VERTEX.y = min(VERTEX.y, cut_height);
+		UV.y = max(UV.y, 1.0 - cut_height);
+	}
+
 	bottom_to_top = 1.0 - UV.y;
-	
+
+	// Wind logic
+	vec2 wind_position = NODE_POSITION_WORLD.xz / 10.0;
+	wind_position -= (TIME + 8.0) * wind_direction * wind_strength;
+
+	current_wind_bend = texture(wind_noise, wind_position).x;
+
+	current_wind_bend *= wind_strength;
+	current_wind_bend *= bottom_to_top * 2.0;
+
+	mat4 inv_model = inverse(MODEL_MATRIX);
+	vec2 local_direction = (inv_model * vec4(wind_direction.x, 0.0, wind_direction.y, 0.0)).xz;
+
+	VERTEX.xz += current_wind_bend * local_direction * wind_bend_strength;
+
+	// Bend away from the object
+	float object_distance = distance(object_position, NODE_POSITION_WORLD);
+	float bend_away_strength = max(object_radius - object_distance, 0.0) / object_radius;
+	vec2 bend_direction = normalize(object_position.xz - NODE_POSITION_WORLD.xz);
+
+	VERTEX.xz -= (inv_model * vec4(bend_direction.x, 0.0, bend_direction.y, 0.0)).xz
+			* bend_away_strength * bottom_to_top;
+	VERTEX.y -= bend_away_strength * bottom_to_top * 0.5;
+
+	// General appearance
 	VERTEX.z += blade_bend * pow(bottom_to_top, 2.0);
 
 	patch_factor = texture(patch_noise, NODE_POSITION_WORLD.xz / patch_scale).r;
@@ -27,8 +72,8 @@ void vertex() {
 }
 
 void fragment() {
-	AO = bottom_to_top;
-	AO_LIGHT_AFFECT = 1.0;
+	AO = bottom_to_top - current_wind_bend * wind_ao_affect;
+	AO_LIGHT_AFFECT = cut_height;
 
 	ALBEDO = mix(color_small, color_large, patch_factor);
 	BACKLIGHT = vec3(0.2);