diff --git a/README.md b/README.md
index 0b51884..814ab54 100644
--- a/README.md
+++ b/README.md
@@ -3,7 +3,9 @@ Release:
         + Benchmark harness
         + Reuse points, pack "nodraw" in high bit of stroke id (probably have at least one more bit, so up to 4 flag configurations)
         + Draw dynamic data (strokes in progress)
-        * Webassembly for core LOD generation
+        + Webassembly for core LOD generation
+        - Webassembly for final buffers
+        - Do not copy memory from wasm and back
         - Z-prepass fringe bug (also, when do we enable the prepass?)
         - Textured quads (pictures, code already written in older version)
         - Resize and move pictures (draw handles)
@@ -34,7 +36,7 @@ Release:
         - Line drawing
         - Undo/redo
     * Polish
-        * Use typedvector where appropriate
+        + Use typedvector where appropriate
         - Show what's happening while the desk is loading (downloading, processing, uploading to gpu)
         - Settings panel for config values (including the setting for "offline mode")
         - Set up VAOs
diff --git a/client/aux.js b/client/aux.js
index 7b3b837..81c39db 100644
--- a/client/aux.js
+++ b/client/aux.js
@@ -125,21 +125,21 @@ function tv_data(tv) {
     return tv.data.subarray(0, tv.size);
 }
 
+function tv_bytes(tv) {
+    return new Uint8Array(tv.data.buffer, 0, tv.size * tv.data.BYTES_PER_ELEMENT);
+}
+
 function tv_ensure(tv, capacity) {
     if (tv.capacity < capacity) {
-        const new_tv = tv_create(tv.class_name, capacity);
-        
-        new_tv.data.set(tv_data(tv));
-        new_tv.size = tv.size;
-
-        return new_tv;
+        const new_data = new tv.class_name(capacity);
+        new_data.set(tv_data(tv));
+        tv.capacity = capacity;
+        tv.data = new_data;
     }
-
-    return tv;
 }
 
 function tv_ensure_by(tv, by) {
-    return tv_ensure(tv, round_to_pow2(tv.size + by, 4096));
+    tv_ensure(tv, round_to_pow2(tv.size + by, 4096));
 }
 
 function tv_add(tv, item) {
diff --git a/client/bvh.js b/client/bvh.js
index e16f7de..f1b34c7 100644
--- a/client/bvh.js
+++ b/client/bvh.js
@@ -172,8 +172,7 @@ function bvh_intersect_quad(bvh, quad, result_buffer) {
         }
 
         if (node.is_leaf) {
-            result_buffer.data[result_buffer.count] = node.stroke_index;
-            result_buffer.count += 1;
+            tv_add(result_buffer, node.stroke_index);
         } else {
             tv_add(bvh.traverse_stack, node.child1);
             tv_add(bvh.traverse_stack, node.child2);
@@ -186,14 +185,10 @@ function bvh_clip(state, context) {
         return;
     }
 
-    if (context.clipped_indices.cap < state.stroke_count) {
-        context.clipped_indices.cap = round_to_pow2(state.stroke_count, 4096);
-        context.clipped_indices.data = new Uint32Array(context.clipped_indices.cap);
-    }
-
-    state.bvh.traverse_stack = tv_ensure(state.bvh.traverse_stack, round_to_pow2(state.stroke_count, 4096));
+    tv_ensure(context.clipped_indices, round_to_pow2(state.stroke_count, 4096))
+    tv_ensure(state.bvh.traverse_stack, round_to_pow2(state.stroke_count, 4096));
 
-    context.clipped_indices.count = 0;
+    tv_clear(context.clipped_indices);
 
     const screen_topleft     = screen_to_canvas(state, {'x': 0, 'y': 0});
     const screen_bottomright = screen_to_canvas(state, {'x': context.canvas.width, 'y': context.canvas.height});
@@ -209,7 +204,7 @@ function bvh_clip(state, context) {
 
     bvh_intersect_quad(state.bvh, screen, context.clipped_indices);
 
-    new Uint32Array(context.clipped_indices.data.buffer, 0, context.clipped_indices.count).sort(); // we need to draw back to front still!
+    tv_data(context.clipped_indices).sort(); // we need to draw back to front still!
 }
 
 function bvh_construct_rec(bvh, vertical, strokes) {
diff --git a/client/client_recv.js b/client/client_recv.js
index e1fa77d..10d2d40 100644
--- a/client/client_recv.js
+++ b/client/client_recv.js
@@ -101,8 +101,14 @@ function des_event(d, state = null) {
 
             const coords = des_f32array(d, point_count * 2);
 
-            state.coordinates = tv_ensure_by(state.coordinates, coords.length);
+            tv_ensure_by(state.coordinates, coords.length);
+            tv_ensure_by(state.coords_from, 1);
+            tv_ensure_by(state.coords_to, 1);
+            
+            tv_add(state.coords_from, state.coordinates.size);
+            tv_add(state.coords_to, state.coordinates.size + point_count * 2);
 
+            // TODO: remove, this is duplicate data 
             event.coords_from = state.coordinates.size;
             event.coords_to = state.coordinates.size + point_count * 2;
             
diff --git a/client/index.html b/client/index.html
index 2bbdaf0..e9268ec 100644
--- a/client/index.html
+++ b/client/index.html
@@ -39,6 +39,7 @@
 
             <label><input type="checkbox" id="debug-red">Simple shader</label>
             <label><input type="checkbox" id="debug-do-prepass">Depth prepass</label>
+            <label><input type="checkbox" id="debug-use-wasm">Use WASM</label>
 
             <div class="flexcol">
                 <label><input type="checkbox" id="debug-limit-from">Limit events from</label>
diff --git a/client/index.js b/client/index.js
index eecd128..dc44cd5 100644
--- a/client/index.js
+++ b/client/index.js
@@ -129,7 +129,7 @@ function start_spinner(state) {
     }
 }
 
-function main() {
+async function main() {
     const state = {
         'online': false,
         'me': null,
@@ -179,18 +179,10 @@ function main() {
 
         'coordinates': tv_create(Float32Array, 4096),
         'line_threshold': tv_create(Float32Array, 4096),
-
-        'segments_from': {
-            'data': null,
-            'count': 0,
-            'cap': 0,
-        },
-
-        'segments': {
-            'data': null,
-            'count': 0,
-            'cap': 0,
-        },
+        'coords_from': tv_create(Uint32Array, 4096),
+        'coords_to': tv_create(Uint32Array, 4096),
+        'segments_from': tv_create(Uint32Array, 4096),
+        'segments': tv_create(Uint32Array, 4096),
 
         'bvh': {
             'nodes': [],
@@ -220,6 +212,7 @@ function main() {
         'debug': {
             'red': false,
             'do_prepass': true,
+            'use_wasm': false,
             'limit_from': false,
             'limit_to': false,
             'render_from': 0,
@@ -230,6 +223,9 @@ function main() {
 
         'stats': {},
         'following_player': null,
+
+
+        'wasm': {},
     };
 
     const context = {
@@ -244,12 +240,7 @@ function main() {
         'dynamic_serializer': serializer_create(config.initial_dynamic_bytes),
         'dynamic_index_serializer': serializer_create(config.initial_dynamic_bytes),
 
-        // TODO: i seem to have a lot of these, maybe make a few utility functions? similar to serializer, but for pure typedarray
-        'clipped_indices': {
-            'data': null,
-            'count': 0,
-            'cap': 0,
-        },
+        'clipped_indices': tv_create(Uint32Array, 4096),
 
         'instance_data_points': tv_create(Float32Array, 4096),
         'instance_data_ids': tv_create(Uint32Array, 4096),
@@ -277,16 +268,16 @@ function main() {
 
     state.desk_id = parts.length > 0 ? parts[parts.length - 1] : 0;
 
+    await init_wasm(state);
+
     init_webgl(state, context);
     init_listeners(state, context);
     init_tools(state);
+
     
     ws_connect(state, context, true);
 
     schedule_draw(state, context);
 
     state.timers.offline_toast = setTimeout(() => ui_offline(), config.initial_offline_timeout);
-
-
-    test_wasm();
 }
diff --git a/client/speed.js b/client/speed.js
index 9b0740c..c5a6abc 100644
--- a/client/speed.js
+++ b/client/speed.js
@@ -1,18 +1,7 @@
-async function test_wasm() {
-    const memory = new WebAssembly.Memory({ initial: 10, maximum: 100 });
+async function init_wasm(state) {
     const results = await WebAssembly.instantiateStreaming(fetch('wasm/lod.wasm'));
-    const numbers_offset = results.instance.exports.alloc(40);
-
-    const numbers = new Uint32Array(results.instance.exports.memory.buffer, numbers_offset, 10);
-
-    for (let i = 0; i < 10; ++i) {
-        numbers[i] = i;
-    }
-
-    console.log(numbers);
-
-    const sum = results.instance.exports.sum(numbers_offset, 10);
-    console.log(sum);
+    state.wasm.exports = results.instance.exports;
+    state.wasm.exports.memory.grow(1024);
 }
 
 function rdp_find_max(state, zoom, coords_from, start, end) {
@@ -55,20 +44,64 @@ function rdp_find_max(state, zoom, coords_from, start, end) {
     return result;
 }
 
+function do_lod_wasm(state, context) {
+    const clipped_indices = state.wasm.exports.alloc(context.clipped_indices.size * 4); 
+    const stroke_coords_from = state.wasm.exports.alloc(state.coords_from.size * 4); 
+    const stroke_coords_to = state.wasm.exports.alloc(state.coords_to.size * 4); 
+    const line_threshold = state.wasm.exports.alloc(state.line_threshold.size * 4);
+    const segments_from = state.wasm.exports.alloc((context.clipped_indices.size + 1) * 4); 
+    const segments = state.wasm.exports.alloc(state.segments.capacity * 4); 
+    const coordinates = state.wasm.exports.alloc(state.coordinates.size * 4);
+
+    const mem = new Uint8Array(state.wasm.exports.memory.buffer);
+
+    mem.set(tv_bytes(context.clipped_indices), clipped_indices);
+    mem.set(tv_bytes(state.coords_from), stroke_coords_from);
+    mem.set(tv_bytes(state.coords_to), stroke_coords_to);
+    mem.set(tv_bytes(state.line_threshold), line_threshold);
+    mem.set(tv_bytes(state.coordinates), coordinates);
+
+    const segment_count = state.wasm.exports.do_lod(
+        clipped_indices, context.clipped_indices.size, state.canvas.zoom,
+        stroke_coords_from, stroke_coords_to,
+        line_threshold, coordinates,
+        segments_from, segments
+    );
+
+    // copy result back
+    const wasm_segments = new Uint32Array(state.wasm.exports.memory.buffer, segments, segment_count);
+    const wasm_segments_from = new Uint32Array(state.wasm.exports.memory.buffer, segments_from, context.clipped_indices.size);
+
+    state.segments.data.set(wasm_segments);
+    state.segments.size = segment_count;
+    
+    state.segments_from.data.set(wasm_segments_from);
+    state.segments_from.size = context.clipped_indices.size + 1;
+
+    state.wasm.exports.total_free();
+
+
+    return segment_count;
+}
+
 function do_lod(state, context) {
+    if (state.debug.use_wasm) {
+        return do_lod_wasm(state, context);
+    }
+
     const zoom = state.canvas.zoom;
     const segments_data = state.segments.data;
     
     let segments_head = 0;
 
-    for (let i = 0; i < context.clipped_indices.count; ++i) {
+    for (let i = 0; i < context.clipped_indices.size; ++i) {
         const stroke_index = context.clipped_indices.data[i];
         const stroke = state.events[stroke_index];
         const point_count = (stroke.coords_to - stroke.coords_from) / 2;
         const coords_from = stroke.coords_from;
 
         if (point_count > state.rdp_traverse_stack.length) {
-            //console.count('allocate')
+            //console.size('allocate')
             state.rdp_traverse_stack = new Uint32Array(round_to_pow2(point_count, 4096));
         }
 
@@ -127,5 +160,9 @@ function do_lod(state, context) {
         }
     }
 
+    state.segments_from.data[context.clipped_indices.size] = segments_head;
+    state.segments_from.size = context.clipped_indices.size + 1;
+    state.segments.size = segments_head;
+
     return segments_head;
 }
diff --git a/client/wasm/lod.c b/client/wasm/lod.c
index db1c3c9..d911079 100644
--- a/client/wasm/lod.c
+++ b/client/wasm/lod.c
@@ -1,6 +1,12 @@
 extern char __heap_base;
 static int allocated;
 
+void
+total_free(void)
+{
+    allocated = 0;
+}
+
 void *
 alloc(int size)
 {
@@ -9,19 +15,6 @@ alloc(int size)
     return(result);
 }
 
-int
-sum(int *numbers, int count)
-{
-    int result = 0;
-    
-    for (int i = 0; i < count; ++i) {
-        result += numbers[i];
-    }
-    
-    return(result);
-}
-
-#if 0
 static int
 rdp_find_max(float *coordinates, float zoom, int coords_from, 
              int segment_start, int segment_end)
@@ -67,8 +60,12 @@ do_lod(int *clipped_indices, int clipped_count, float zoom,
        float *line_threshold, float *coordinates,
        int *segments_from, int *segments)
 {
+    if (clipped_count == 0) {
+        return(0);
+    }
+    
     int segments_head = 0;
-    int stack[4096];
+    int stack[4096]; // TODO: what's a reasonable max size for this?
     
     for (int i = 0; i < clipped_count; ++i) {
         int stroke_index = clipped_indices[i];
@@ -131,7 +128,8 @@ do_lod(int *clipped_indices, int clipped_count, float zoom,
             line_threshold[stroke_index] = zoom;
         }
     }
+
+    segments_from[clipped_count] = segments_head;
     
     return(segments_head);
 }
-#endif
\ No newline at end of file
diff --git a/client/wasm/lod.wasm b/client/wasm/lod.wasm
index e9e084a..9c0c4f3 100755
Binary files a/client/wasm/lod.wasm and b/client/wasm/lod.wasm differ
diff --git a/client/webgl_geometry.js b/client/webgl_geometry.js
index 9970f2d..0b252bd 100644
--- a/client/webgl_geometry.js
+++ b/client/webgl_geometry.js
@@ -38,31 +38,19 @@ function geometry_prepare_stroke(state) {
 
 
 function geometry_write_instances(state, context) {
-    if (state.segments_from.cap < context.clipped_indices.count + 1) {
-        state.segments_from.cap = round_to_pow2(context.clipped_indices.count + 1, 4096);
-        state.segments_from.data = new Uint32Array(state.segments_from.cap);
-    }
-
-    if (state.segments.cap < state.coordinates.size / 2) {
-        state.segments.cap = round_to_pow2(state.coordinates.size, 4096); 
-        state.segments.data = new Uint32Array(state.segments.cap);
-    }
+    tv_ensure(state.segments_from, round_to_pow2(context.clipped_indices.size + 1, 4096));
+    tv_ensure(state.segments, round_to_pow2(state.coordinates.size / 2, 4096)); 
     
-    state.segments_from.count = 0;
-    state.segments.count = 0;
+    tv_clear(state.segments_from);
+    tv_clear(state.segments);
 
     state.stats.rdp_max_count = 0;
     state.stats.rdp_segments = 0;
 
     const segment_count = do_lod(state, context);
 
-    state.segments.count = segment_count;
-    state.segments_from.data[context.clipped_indices.count] = state.segments.count;
-    state.segments_from.count = context.clipped_indices.count + 1;
-        
-    context.instance_data_points = tv_ensure(context.instance_data_points, state.segments.count * 2);
-    context.instance_data_ids = tv_ensure(context.instance_data_ids, state.segments.count);
-
+    tv_ensure(context.instance_data_points, state.segments.size * 2);
+    tv_ensure(context.instance_data_ids, state.segments.size);
 
     tv_clear(context.instance_data_points);
     tv_clear(context.instance_data_ids);
@@ -72,10 +60,11 @@ function geometry_write_instances(state, context) {
     const segments = state.segments.data;
     const coords = state.coordinates.data;
     const events = state.events;
-
-    for (let i = 0; i < state.segments_from.count - 1; ++i) {
+    
+    // TODO: move this loop to WASM
+    for (let i = 0; i < state.segments_from.size - 1; ++i) {
         const stroke_index = clipped[i];
-        const coords_from = events[stroke_index].coords_from;
+        const coords_from = state.events[stroke_index].coords_from;
         const from = segments_from[i];
         const to = segments_from[i + 1];
 
@@ -100,7 +89,7 @@ function geometry_write_instances(state, context) {
 
     if (config.debug_print) console.debug('instances:', state.segments.count, 'rdp max:', state.stats.rdp_max_count, 'rdp segments:', state.stats.rdp_segments);
 
-    return state.segments.count;
+    return state.segments.size;
 }
 
 function geometry_add_stroke(state, context, stroke, stroke_index, skip_bvh = false) {
@@ -111,7 +100,7 @@ function geometry_add_stroke(state, context, stroke, stroke_index, skip_bvh = fa
 
     context.stroke_data = ser_ensure_by(context.stroke_data, config.bytes_per_stroke);
 
-    state.line_threshold = tv_ensure(state.line_threshold, round_to_pow2(state.stroke_count, 4096));
+    tv_ensure(state.line_threshold, round_to_pow2(state.stroke_count, 4096));
     tv_add(state.line_threshold, -1);
 
     const color_u32 = stroke.color;
@@ -159,8 +148,8 @@ function recompute_dynamic_data(state, context) {
         }
     }
 
-    context.dynamic_instance_data = tv_ensure(context.dynamic_instance_points, round_to_pow2(total_points * 2, 4096));
-    context.dynamic_instance_ids = tv_ensure(context.dynamic_instance_ids, round_to_pow2(total_points, 4096));
+    tv_ensure(context.dynamic_instance_points, round_to_pow2(total_points * 2, 4096));
+    tv_ensure(context.dynamic_instance_ids, round_to_pow2(total_points, 4096));
 
     tv_clear(context.dynamic_instance_points);
     tv_clear(context.dynamic_instance_ids);
diff --git a/client/webgl_listeners.js b/client/webgl_listeners.js
index f89e8d7..65b3d4f 100644
--- a/client/webgl_listeners.js
+++ b/client/webgl_listeners.js
@@ -26,6 +26,7 @@ function debug_panel_init(state, context) {
     document.getElementById('debug-do-prepass').checked = state.debug.do_prepass;
     document.getElementById('debug-limit-from').checked = state.debug.limit_from;
     document.getElementById('debug-limit-to').checked = state.debug.limit_to;
+    document.getElementById('debug-use-wasm').checked = state.debug.use_wasm;
 
     document.getElementById('debug-red').addEventListener('change', (e) => {
         state.debug.red = e.target.checked;
@@ -37,6 +38,11 @@ function debug_panel_init(state, context) {
         schedule_draw(state, context);
     });
     
+    document.getElementById('debug-use-wasm').addEventListener('change', (e) => {
+        state.debug.use_wasm = e.target.checked;
+        schedule_draw(state, context);
+    });
+
     document.getElementById('debug-limit-from').addEventListener('change', (e) => {
         state.debug.limit_from = e.target.checked;
         schedule_draw(state, context);