surface points on gpu

compute_test.gd

@@ -28,6 +28,21 @@ func compute(world_size: int, threshold: float):
 	uniform_buf.binding = 0 # this needs to match the "binding" in our shader file
 	uniform_buf.add_id(buffer)
 	
+	# Prepare our data. We use floats in the shader, so we need 32 bit.
+	var surface_total = world_size * world_size * world_size * 3
+	var surface_input := PackedFloat32Array()
+	surface_input.resize(surface_total)
+	var surface_input_bytes := surface_input.to_byte_array()
+
+	# Create a storage buffer that can hold our float values.
+	var surface_buffer := rd.storage_buffer_create(surface_input_bytes.size(), surface_input_bytes)
+
+	# Create a uniform to assign the buffer to the rendering device
+	var surface_uniform_buf := RDUniform.new()
+	surface_uniform_buf.uniform_type = RenderingDevice.UNIFORM_TYPE_STORAGE_BUFFER
+	surface_uniform_buf.binding = 2 # this needs to match the "binding" in our shader file
+	surface_uniform_buf.add_id(surface_buffer)
+	
 	var peer := StreamPeerBuffer.new()
 	peer.put_32(world_size)
 	peer.put_float(threshold)
@@ -42,7 +57,7 @@ func compute(world_size: int, threshold: float):
 	uniform_params.binding = 1
 	uniform_params.add_id(params_buffer)
 
-	var uniform_set := rd.uniform_set_create([uniform_params, uniform_buf], shader, 0) # the last parameter (the 0) needs to match the "set" in our shader file
+	var uniform_set := rd.uniform_set_create([uniform_params, uniform_buf, surface_uniform_buf], shader, 0) # the last parameter (the 0) needs to match the "set" in our shader file
 	
 	# Create a compute pipeline
 	var pipeline := rd.compute_pipeline_create(shader)
@@ -59,12 +74,31 @@ func compute(world_size: int, threshold: float):
 	rd.submit()
 	rd.sync()
 	# Read back the data from the buffer
-	var output_bytes := rd.buffer_get_data(buffer)
+	var output_bytes := rd.buffer_get_data(surface_buffer)
 	var output := output_bytes.to_float32_array()
 	
 	rd.free_rid(buffer)
-	
 	rd.free_rid(params_buffer)
-	return output
+	rd.free_rid(surface_buffer)
+	return build_surface_dict(world_size, output)
 
-	
+func build_surface_dict(world_size: int, flat_buffer: PackedFloat32Array) -> Dictionary:
+	var dict := {}
+	var total = world_size * world_size * world_size
+
+	for idx in total:
+		var base = idx * 3
+		var x = flat_buffer[base]
+		var y = flat_buffer[base + 1]
+		var z = flat_buffer[base + 2]
+
+		var voxel_x = idx % world_size
+		var voxel_y = (idx / world_size) % world_size
+		var voxel_z = idx / (world_size * world_size)
+
+		var voxel_id = Vector3i(voxel_x, voxel_y, voxel_z)
+		var surface_pos = Vector3(x, y, z)
+
+		dict[voxel_id] = surface_pos
+
+	return dict

sdf_shader.glsl

@@ -15,10 +15,21 @@ layout(set = 0, binding = 1) uniform Params {
     float threshold;
 } params;
 
+layout(set = 0, binding = 2) buffer SurfaceBuffer {
+    float surface_points[]; 
+} surface;
+
 uint index3(uint x, uint y, uint z) {
     return x + y * params.world_size + z * params.world_size * params.world_size;
 }
 
+void store_surface_point(uint idx, vec3 pos) {
+    uint base = idx * 3u;
+    surface.surface_points[base + 0u] = pos.x;
+    surface.surface_points[base + 1u] = pos.y;
+    surface.surface_points[base + 2u] = pos.z;
+}
+
 void main() {
     uvec3 id = gl_GlobalInvocationID;
     if (id.x >= uint(params.world_size) ||
@@ -26,7 +37,56 @@ void main() {
         id.z >= uint(params.world_size))
         return;
 
+    const ivec3 SURFACE_AXIS[8] = ivec3[](
+	      ivec3(1,0,0),
+	      ivec3(0,1,0),
+	      ivec3(0,0,1),
+	      ivec3(1,0,1),
+	      ivec3(0,1,1),
+	      ivec3(1,1,0),
+	      ivec3(1,1,1),
+	      ivec3(0,0,0)
+      );
+
     vec3 p = vec3(id) - params.world_size / 2 + 1;
     float d = length(p) - params.threshold;
-    voxels.sample_points[index3(id.x, id.y, id.z)] = d;
+    uint idx = index3(id.x, id.y, id.z);
+    voxels.sample_points[idx] = d;
+
+    int previous_sign = 0;
+    vec3 previous_sample_point_coords = vec3(id.x, id.y, id.z);
+    float previous_sample_point_distance = 0.0;
+    vec3 intersection_points_sum = vec3(0.0, 0.0, 0.0);
+    uint intersection_points_count = 0u;
+    for (int sample_point_to_check_index = 0; sample_point_to_check_index < 8; sample_point_to_check_index++){
+      ivec3 sample_point_to_check = ivec3(id) + SURFACE_AXIS[sample_point_to_check_index];
+      
+      // bounds check
+      if (sample_point_to_check.x < 0 || sample_point_to_check.y < 0 || sample_point_to_check.z < 0) continue;
+      if (uint(sample_point_to_check.x) >= params.world_size || uint(sample_point_to_check.y) >= params.world_size || uint(sample_point_to_check.z) >= params.world_size) continue;
+      
+      uint buffer_index = index3(uint(sample_point_to_check.x), uint(sample_point_to_check.y), uint(sample_point_to_check.z));
+      float sample_point_distance_from_sdf = voxels.sample_points[buffer_index];
+      
+      int current_sign = (sample_point_distance_from_sdf >= 0.0 ? 1 : -1);
+      
+      if (previous_sign != 0 && current_sign != previous_sign) {
+        float t = previous_sample_point_distance / (previous_sample_point_distance - sample_point_distance_from_sdf);
+        vec3 intersect = mix(vec3(previous_sample_point_coords), vec3(sample_point_to_check), t);
+        intersection_points_sum += intersect;
+        intersection_points_count++;
+      }
+
+      previous_sign = current_sign;
+      previous_sample_point_distance = sample_point_distance_from_sdf;
+      previous_sample_point_coords = sample_point_to_check;
+    } 
+
+    if (intersection_points_count > 0u) {
+        vec3 avg = intersection_points_sum / float(intersection_points_count);
+        store_surface_point(idx, avg);
+    } else {
+        store_surface_point(idx, vec3(0.0)); // no surface
+    }
+
 }

smooth_world.gd

@@ -20,6 +20,7 @@ var gpu_sdf
 @export var clear_the_thing: bool = false
 
 var sdf_buffer = []
+var surface_points_buffer = []
 
 var color = Color.CORAL
 var surface_point_color = Color.CRIMSON
@@ -33,9 +34,10 @@ func _ready() -> void:
 
 func _process(_delta: float) -> void:
 	clear()
-	sdf_buffer = gpu_sdf.compute(world_size, RADIUS)
-	if !sdf_buffer.is_empty():
-		create_surface_points()
+	surface_points = gpu_sdf.compute(world_size, RADIUS)
+	if !surface_points.is_empty():
+		#create_surface_points_gpu()
+		#create_surface_points()
 		if show_surface_points:
 			draw_surface_points()
 		if show_surface:
@@ -51,6 +53,9 @@ func clear():
 		if child is MeshInstance3D:
 			child.queue_free()
 
+func get_index_from_coords(coords: Vector3i):
+	return coords.x + coords.y * world_size + coords.z * world_size * world_size
+
 func draw_sample_points():
 	for x in range(world_size):
 		for y in range(world_size):
@@ -60,12 +65,10 @@ func draw_sample_points():
 					#DebugDraw3D.draw_text(Vector3i(x, y, z), str(Vector3i(x, y, z)))
 
 func draw_surface_points():
-	for x in range(world_size):
-		for y in range(world_size):
-			for z in range(world_size):
-				if surface_points.has(Vector3i(x, y, z)):
-					DebugDraw3D.draw_square(surface_points[Vector3i(x, y, z)].position , 0.3, surface_point_color)
-					DebugDraw3D.draw_text(surface_points[Vector3i(x, y, z)].position, str(surface_points[Vector3i(x, y, z)].position))
+	for surface_point in surface_points:
+		if surface_points[surface_point] != Vector3(0, 0, 0):
+			DebugDraw3D.draw_square(surface_points[surface_point] , 0.3, surface_point_color)
+			#DebugDraw3D.draw_text(surface_points[Vector3i(x, y, z)], str(surface_points[Vector3i(x, y, z)]))
 
 func create_surface_points():
 	for x in range(world_size):

smooth_world.tscn

@@ -5,3 +5,4 @@
 [node name="SmoothWorld" type="Node3D"]
 script = ExtResource("1_4h467")
 RADIUS = 6.789
+show_surface_points = true