Untie splat rendering components from viser-specific internals

examples/experimental/gaussian_splats.py

@@ -129,14 +129,21 @@ def _(event: viser.GuiEvent) -> None:
             raise SystemExit("Please provide a filepath to a .splat or .ply file.")
 
         server.scene.add_transform_controls(f"/{i}")
-        server.scene._add_gaussian_splats(
+        gs_handle = server.scene._add_gaussian_splats(
             f"/{i}/gaussian_splats",
             centers=splat_data["centers"],
             rgbs=splat_data["rgbs"],
             opacities=splat_data["opacities"],
             covariances=splat_data["covariances"],
         )
 
+        remove_button = server.gui.add_button(f"Remove splat object {i}")
+
+        @remove_button.on_click
+        def _(_, gs_handle=gs_handle) -> None:
+            gs_handle.remove()
+            remove_button.remove()
+
     while True:
         time.sleep(10.0)
 

src/viser/client/src/App.tsx

@@ -45,13 +45,9 @@ import { useDisclosure } from "@mantine/hooks";
 import { rayToViserCoords } from "./WorldTransformUtils";
 import { ndcFromPointerXy, opencvXyFromPointerXy } from "./ClickUtils";
 import { theme } from "./AppTheme";
-import {
-  GaussianSplatsContext,
-  useGaussianSplatStore,
-} from "./Splatting/SplatContext";
 import { FrameSynchronizedMessageHandler } from "./MessageHandler";
 import { PlaybackFromFile } from "./FilePlayback";
-import GlobalGaussianSplats from "./Splatting/GaussianSplats";
+import { SplatRenderContext } from "./Splatting/GaussianSplats";
 import { BrowserWarning } from "./BrowserWarning";
 
 export type ViewerContextContents = {
@@ -267,12 +263,9 @@ function ViewerContents({ children }: { children: React.ReactNode }) {
               })}
             >
               <Viewer2DCanvas />
-              <GaussianSplatsContext.Provider value={useGaussianSplatStore()}>
-                <ViewerCanvas>
-                  <GlobalGaussianSplats />
-                  <FrameSynchronizedMessageHandler />
-                </ViewerCanvas>
-              </GaussianSplatsContext.Provider>
+              <ViewerCanvas>
+                <FrameSynchronizedMessageHandler />
+              </ViewerCanvas>
               {viewer.useGui((state) => state.theme.show_logo) &&
               viewer.messageSource == "websocket" ? (
                 <ViserLogo />
@@ -453,7 +446,9 @@ function ViewerCanvas({ children }: { children: React.ReactNode }) {
       <AdaptiveDpr />
       <SceneContextSetter />
       <SynchronizedCameraControls />
-      <SceneNodeThreeObject name="" parent={null} />
+      <SplatRenderContext>
+        <SceneNodeThreeObject name="" parent={null} />
+      </SplatRenderContext>
       <Environment path="hdri/" files="potsdamer_platz_1k.hdr" />
       <directionalLight color={0xffffff} intensity={1.0} position={[0, 1, 0]} />
       <directionalLight
@@ -473,7 +468,7 @@ function AdaptiveDpr() {
       ms={100}
       iterations={5}
       step={0.2}
-      bounds={(refreshrate) => (refreshrate > 90 ? [40, 80] : [40, 50])}
+      bounds={(refreshrate) => (refreshrate > 90 ? [80, 90] : [50, 60])}
       onChange={({ factor, fps, refreshrate }) => {
         const dpr = window.devicePixelRatio * (0.2 + 0.8 * factor);
         console.log(

src/viser/client/src/MessageHandler.tsx

@@ -29,7 +29,7 @@ import GeneratedGuiContainer from "./ControlPanel/Generated";
 import { Paper, Progress } from "@mantine/core";
 import { IconCheck } from "@tabler/icons-react";
 import { computeT_threeworld_world } from "./WorldTransformUtils";
-import { GaussianSplatsContext } from "./Splatting/SplatContext";
+import { SplatObject } from "./Splatting/GaussianSplats";
 
 /** Convert raw RGB color buffers to linear color buffers. **/
 function threeColorBufferFromUint8Buffer(colors: ArrayBuffer) {
@@ -51,10 +51,6 @@ function useMessageHandler() {
   const viewer = useContext(ViewerContext)!;
   const ContextBridge = useContextBridge();
 
-  const splatContext = useContext(GaussianSplatsContext)!;
-  const setGaussianBuffer = splatContext((state) => state.setBuffer);
-  const removeGaussianBuffer = splatContext((state) => state.removeBuffer);
-
   // We could reduce the redundancy here if we wanted to.
   // https://github.com/nerfstudio-project/viser/issues/39
   const removeSceneNode = viewer.useSceneTree((state) => state.removeSceneNode);
@@ -970,25 +966,22 @@ function useMessageHandler() {
         return;
       }
       case "GaussianSplatsMessage": {
-        setGaussianBuffer(
-          message.name,
-          new Uint32Array(
-            message.buffer.buffer.slice(
-              message.buffer.byteOffset,
-              message.buffer.byteOffset + message.buffer.byteLength,
-            ),
-          ),
-        );
         addSceneNodeMakeParents(
-          new SceneNode<THREE.Group>(
-            message.name,
-            (ref) => {
-              return <group ref={ref}></group>;
-            },
-            () => {
-              removeGaussianBuffer(message.name);
-            },
-          ),
+          new SceneNode<THREE.Group>(message.name, (ref) => {
+            return (
+              <SplatObject
+                ref={ref}
+                buffer={
+                  new Uint32Array(
+                    message.buffer.buffer.slice(
+                      message.buffer.byteOffset,
+                      message.buffer.byteOffset + message.buffer.byteLength,
+                    ),
+                  )
+                }
+              />
+            );
+          }),
         );
         return;
       }

src/viser/client/src/Splatting/GaussianSplats.tsx

@@ -1,14 +1,85 @@
+/** Gaussian splatting implementation for viser.
+ *
+ * This borrows heavily from existing open-source implementations. Particularly
+ * useful references:
+ * - https://github.com/quadjr/aframe-gaussian-splatting
+ * - https://github.com/antimatter15/splat
+ * - https://github.com/pmndrs/drei
+ * - https://github.com/vincent-lecrubier-skydio/react-three-fiber-gaussian-splat
+ *
+ * Usage should look like:
+ *
+ * <Canvas>
+ *   <SplatRenderContext>
+ *     <SplatObject buffer={buffer} />
+ *   </SplatRenderContext>
+ * </Canvas>
+ *
+ * Where `buffer` contains serialized Gaussian attributes. SplatObjects are
+ * globally sorted by a worker (with some help from WebAssembly + SIMD
+ * intrinsics), and then rendered as a single threejs mesh. Unlike other R3F
+ * implementations that we're aware of, this enables correct compositing
+ * between multiple splat objects.
+ */
+
 import React from "react";
 import * as THREE from "three";
 import SplatSortWorker from "./SplatSortWorker?worker";
 import { useFrame, useThree } from "@react-three/fiber";
 import { shaderMaterial } from "@react-three/drei";
-import { GaussianSplatsContext } from "./SplatContext";
-import { ViewerContext } from "../App";
 import { SorterWorkerIncoming } from "./SplatSortWorker";
+import { create } from "zustand";
+import { Object3D } from "three";
+
+/**Global splat state.*/
+interface SplatState {
+  groupBufferFromId: { [id: string]: Uint32Array };
+  nodeRefFromId: React.MutableRefObject<{
+    [name: string]: undefined | Object3D;
+  }>;
+  setBuffer: (id: string, buffer: Uint32Array) => void;
+  removeBuffer: (id: string) => void;
+}
 
-function postToWorker(worker: Worker, message: SorterWorkerIncoming) {
-  worker.postMessage(message);
+/**Hook for creating global splat state.*/
+function useGaussianSplatStore() {
+  const nodeRefFromId = React.useRef({});
+  return React.useState(() =>
+    create<SplatState>((set) => ({
+      groupBufferFromId: {},
+      nodeRefFromId: nodeRefFromId,
+      setBuffer: (id, buffer) => {
+        return set((state) => ({
+          groupBufferFromId: { ...state.groupBufferFromId, [id]: buffer },
+        }));
+      },
+      removeBuffer: (id) => {
+        return set((state) => {
+          // eslint-disable-next-line @typescript-eslint/no-unused-vars
+          const { [id]: _, ...buffers } = state.groupBufferFromId;
+          return { groupBufferFromId: buffers };
+        });
+      },
+    })),
+  )[0];
+}
+const GaussianSplatsContext = React.createContext<ReturnType<
+  typeof useGaussianSplatStore
+> | null>(null);
+
+/**Provider for creating splat rendering context.*/
+export function SplatRenderContext({
+  children,
+}: {
+  children: React.ReactNode;
+}) {
+  const store = useGaussianSplatStore();
+  return (
+    <GaussianSplatsContext.Provider value={store}>
+      <SplatRenderer />
+      {children}
+    </GaussianSplatsContext.Provider>
+  );
 }
 
 const GaussianSplatMaterial = /* @__PURE__ */ shaderMaterial(
@@ -52,14 +123,6 @@ const GaussianSplatMaterial = /* @__PURE__ */ shaderMaterial(
   out vec4 vRgba;
   out vec2 vPosition;
 
-	float hash2D(vec2 value) {
-		return fract( 1.0e4 * sin( 17.0 * value.x + 0.1 * value.y ) * ( 0.1 + abs( sin( 13.0 * value.y + value.x ) ) ) );
-	}
-
-	float hash3D(vec3 value) {
-		return hash2D( vec2( hash2D( value.xy ), value.z ) );
-	}
-
   // Function to fetch and construct the i-th transform matrix using texelFetch
   mat4 getGroupTransform(uint i) {
     // Calculate the base index for the i-th transform.
@@ -80,14 +143,16 @@ const GaussianSplatMaterial = /* @__PURE__ */ shaderMaterial(
   void main () {
     // Get position + scale from float buffer.
     ivec2 texSize = textureSize(textureBuffer, 0);
-    ivec2 texPos0 = ivec2((sortedIndex * 2u) % uint(texSize.x), (sortedIndex * 2u) / uint(texSize.x));
+    uint texStart = sortedIndex << 1u;
+    ivec2 texPos0 = ivec2(texStart % uint(texSize.x), texStart / uint(texSize.x));
+
 
     // Fetch from textures.
     uvec4 floatBufferData = texelFetch(textureBuffer, texPos0, 0);
     mat4 T_camera_group = getGroupTransform(floatBufferData.w);
 
     // Any early return will discard the fragment.
-    gl_Position = vec4(0.0, 0.0, 2000.0, 1.0);
+    gl_Position = vec4(0.0, 0.0, 2.0, 1.0);
 
     // Get center wrt camera. modelViewMatrix is T_cam_world.
     vec3 center = uintBitsToFloat(floatBufferData.xyz);
@@ -100,7 +165,7 @@ const GaussianSplatMaterial = /* @__PURE__ */ shaderMaterial(
       return;
 
     // Read covariance terms.
-    ivec2 texPos1 = ivec2((sortedIndex * 2u + 1u) % uint(texSize.x), (sortedIndex * 2u + 1u) / uint(texSize.x));
+    ivec2 texPos1 = ivec2((texStart + 1u) % uint(texSize.x), (texStart + 1u) / uint(texSize.x));
     uvec4 intBufferData = texelFetch(textureBuffer, texPos1, 0);
 
     // Get covariance terms from int buffer.
@@ -111,7 +176,7 @@ const GaussianSplatMaterial = /* @__PURE__ */ shaderMaterial(
 
     // Transition in.
     float startTime = 0.8 * float(sortedIndex) / float(numGaussians);
-    float cov_scale = clamp((transitionInState - startTime) / 0.2f, 0.0f, 1.0f);  // min() can freeze here. Not sure why...
+    float cov_scale = smoothstep(startTime, startTime + 0.2, transitionInState);
 
     // Do the actual splatting.
     mat3 chol = mat3(
@@ -152,10 +217,7 @@ const GaussianSplatMaterial = /* @__PURE__ */ shaderMaterial(
 
     // Throw the Gaussian off the screen if it's too close, too far, or too small.
     float weightedDeterminant = vRgba.a * (diag1 * diag2 - offDiag * offDiag);
-    if (weightedDeterminant < 0.1)
-      return;
-    // This is not principled. It just makes things faster.
-    if (weightedDeterminant < 1.0 && hash3D(center) < weightedDeterminant)
+    if (weightedDeterminant < 0.5)
       return;
     vPosition = position.xy;
 
@@ -182,16 +244,48 @@ const GaussianSplatMaterial = /* @__PURE__ */ shaderMaterial(
   }`,
 );
 
+export const SplatObject = React.forwardRef<
+  THREE.Group,
+  {
+    buffer: Uint32Array;
+  }
+>(function SplatObject({ buffer }, ref) {
+  const splatContext = React.useContext(GaussianSplatsContext)!;
+  const setBuffer = splatContext((state) => state.setBuffer);
+  const removeBuffer = splatContext((state) => state.removeBuffer);
+  const nodeRefFromId = splatContext((state) => state.nodeRefFromId);
+  const name = React.useMemo(() => crypto.randomUUID(), [buffer]);
+
+  const [obj, setRef] = React.useState<THREE.Group | null>(null);
+
+  React.useEffect(() => {
+    if (obj === null) return;
+    setBuffer(name, buffer);
+    if (ref !== null) {
+      if ("current" in ref) {
+        ref.current = obj;
+      } else {
+        ref(obj);
+      }
+    }
+    nodeRefFromId.current[name] = obj;
+    return () => {
+      removeBuffer(name);
+      delete nodeRefFromId.current[name];
+    };
+  }, [obj]);
+
+  return <group ref={setRef}></group>;
+});
+
 /** External interface. Component should be added to the root of canvas.  */
-export default function GlobalGaussianSplats() {
-  const viewer = React.useContext(ViewerContext)!;
+function SplatRenderer() {
   const splatContext = React.useContext(GaussianSplatsContext)!;
-  const groupBufferFromName = splatContext(
-    (state) => state.groupBufferFromName,
-  );
+  const groupBufferFromId = splatContext((state) => state.groupBufferFromId);
+  const nodeRefFromId = splatContext((state) => state.nodeRefFromId);
 
   // Consolidate Gaussian groups into a single buffer.
-  const merged = mergeGaussianGroups(groupBufferFromName);
+  const merged = mergeGaussianGroups(groupBufferFromId);
   const meshProps = useGaussianMeshProps(
     merged.gaussianBuffer,
     merged.numGroups,
@@ -213,7 +307,11 @@ export default function GlobalGaussianSplats() {
       initializedBufferTexture = true;
     }
   };
-  postToWorker(sortWorker, {
+  function postToWorker(message: SorterWorkerIncoming) {
+    sortWorker.postMessage(message);
+  }
+
+  postToWorker({
     setBuffer: merged.gaussianBuffer,
     setGroupIndices: merged.groupIndices,
   });
@@ -224,7 +322,7 @@ export default function GlobalGaussianSplats() {
       meshProps.textureBuffer.dispose();
       meshProps.geometry.dispose();
       meshProps.material.dispose();
-      postToWorker(sortWorker, { close: true });
+      postToWorker({ close: true });
     };
   });
 
@@ -267,10 +365,8 @@ export default function GlobalGaussianSplats() {
     const T_camera_world = state.camera.matrixWorldInverse;
     const groupVisibles: boolean[] = [];
     let visibilitiesChanged = false;
-    for (const [groupIndex, name] of Object.keys(
-      groupBufferFromName,
-    ).entries()) {
-      const node = viewer.nodeRefFromName.current[name];
+    for (const [groupIndex, name] of Object.keys(groupBufferFromId).entries()) {
+      const node = nodeRefFromId.current[name];
       if (node === undefined) continue;
       tmpT_camera_group.copy(T_camera_world).multiply(node.matrixWorld);
       const colMajorElements = tmpT_camera_group.elements;
@@ -312,7 +408,7 @@ export default function GlobalGaussianSplats() {
 
     if (groupsMovedWrtCam) {
       // Gaussians need to be re-sorted.
-      postToWorker(sortWorker, {
+      postToWorker({
         setTz_camera_groups: Tz_camera_groups,
       });
     }