feat: volume rendering show value in layer bar

src/volume_rendering/volume_render_layer.ts

@@ -17,14 +17,17 @@
 import { ChunkState } from "#src/chunk_manager/base.js";
 import { ChunkRenderLayerFrontend } from "#src/chunk_manager/frontend.js";
 import type { CoordinateSpace } from "#src/coordinate_transform.js";
-import type { VisibleLayerInfo } from "#src/layer/index.js";
+import type { PickState, VisibleLayerInfo } from "#src/layer/index.js";
 import type { PerspectivePanel } from "#src/perspective_view/panel.js";
 import type {
   PerspectiveViewReadyRenderContext,
   PerspectiveViewRenderContext,
 } from "#src/perspective_view/render_layer.js";
 import { PerspectiveViewRenderLayer } from "#src/perspective_view/render_layer.js";
-import type { RenderLayerTransformOrError } from "#src/render_coordinate_transform.js";
+import {
+  getChunkPositionFromCombinedGlobalLocalPositions,
+  type RenderLayerTransformOrError,
+} from "#src/render_coordinate_transform.js";
 import type { RenderScaleHistogram } from "#src/render_scale_statistics.js";
 import {
   numRenderScaleHistogramBins,
@@ -222,6 +225,9 @@ export class VolumeRenderingRenderLayer extends PerspectiveViewRenderLayer {
   private modeOverride: TrackableVolumeRenderingModeValue;
   private vertexIdHelper: VertexIdHelper;
   private dataHistogramSpecifications: HistogramSpecifications;
+  private inverseModelViewProjection: mat4;
+  private tempChunkPosition: Float32Array;
+  private currentTransformedSources: TransformedVolumeSource[] | null = null;
 
   private shaderGetter: ParameterizedContextDependentShaderGetter<
     { emitter: ShaderModule; chunkFormat: ChunkFormat; wireFrame: boolean },
@@ -257,7 +263,9 @@ export class VolumeRenderingRenderLayer extends PerspectiveViewRenderLayer {
     super();
     this.gain = options.gain;
     this.multiscaleSource = options.multiscaleSource;
+    this.tempChunkPosition = new Float32Array(options.multiscaleSource.rank);
     this.transform = options.transform;
+    this.inverseModelViewProjection = mat4.create();
     this.channelCoordinateSpace = options.channelCoordinateSpace;
     this.shaderControlState = options.shaderControlState;
     this.localPosition = options.localPosition;
@@ -367,7 +375,7 @@ void emitRGBA(vec4 rgba) {
             glsl_handleMaxProjectionUpdate = `
   float newIntensity = getIntensity();
   bool intensityChanged = newIntensity > savedIntensity;
-  savedIntensity = intensityChanged ? newIntensity : savedIntensity; 
+  savedIntensity = intensityChanged ? newIntensity : savedIntensity;
   savedDepth = intensityChanged ? depthAtRayPosition : savedDepth;
   outputColor = intensityChanged ? newColor : outputColor;
   emit(outputColor, savedDepth, savedIntensity, uPickId);
@@ -657,6 +665,13 @@ outputValue = vec4(1.0, 1.0, 1.0, 1.0);
       this.transform.changed.add(this.redrawNeeded.dispatch),
     );
     this.registerDisposer(this.mode.changed.add(this.redrawNeeded.dispatch));
+    this.registerDisposer(
+      this.mode.changed.add(() => {
+        if (this.mode.value === VolumeRenderingModes.OFF) {
+          this.currentTransformedSources = null;
+        }
+      }),
+    );
     this.registerDisposer(
       this.shaderControlState.fragmentMain.changed.add(
         this.redrawNeeded.dispatch,
@@ -738,9 +753,10 @@ outputValue = vec4(1.0, 1.0, 1.0, 1.0);
       VolumeRenderingAttachmentState
     >,
   ) {
-    if (!renderContext.emitColor) return;
     const allSources = attachment.state!.sources.value;
-    if (allSources.length === 0) return;
+    this.currentTransformedSources =
+      allSources.length === 0 ? null : allSources[0];
+    if (!renderContext.emitColor || allSources.length === 0) return;
     let curPhysicalSpacing = 0;
     let curOptimalSamples = 0;
     let curHistogramInformation: HistogramInformation = {
@@ -928,9 +944,9 @@ outputValue = vec4(1.0, 1.0, 1.0, 1.0);
           projectionParameters.viewProjectionMat,
           chunkLayout.transform,
         );
+        const { inverseModelViewProjection } = this;
         const clippingPlanes = tempVisibleVolumetricClippingPlanes;
         getFrustrumPlanes(clippingPlanes, modelViewProjection);
-        const inverseModelViewProjection = mat4.create();
         mat4.invert(inverseModelViewProjection, modelViewProjection);
         const { near, far, adjustedNear, adjustedFar } =
           getVolumeRenderingNearFarBounds(
@@ -1263,6 +1279,51 @@ outputValue = vec4(1.0, 1.0, 1.0, 1.0);
       restoreDrawingBuffersAndState();
     }
   }
+  // The pick ID encodes no spatial data; return null so UserLayer.getValueAt
+  // falls through to getValueAt() which looks up the voxel value from the depth-derived position if in max or min mode.
+  transformPickedValue(_pickState: PickState) {
+    return null;
+  }
+
+  getValueAt(globalPosition: Float32Array) {
+    const { currentTransformedSources, tempChunkPosition } = this;
+    if (currentTransformedSources === null) return null;
+    const rank = tempChunkPosition.length;
+    for (const {
+      source,
+      chunkTransform,
+      lowerClipBound,
+      upperClipBound,
+    } of currentTransformedSources) {
+      if (
+        !getChunkPositionFromCombinedGlobalLocalPositions(
+          tempChunkPosition,
+          globalPosition,
+          this.localPosition.value,
+          chunkTransform.layerRank,
+          chunkTransform.combinedGlobalLocalToChunkTransform,
+        )
+      ) {
+        continue;
+      }
+      let outOfBounds = false;
+      for (let i = 0; i < rank; ++i) {
+        if (
+          tempChunkPosition[i] < lowerClipBound[i] ||
+          tempChunkPosition[i] >= upperClipBound[i]
+        ) {
+          outOfBounds = true;
+          break;
+        }
+      }
+      if (outOfBounds) continue;
+      const result = source.getValueAt(tempChunkPosition, chunkTransform);
+      if (result != null) {
+        return result;
+      }
+    }
+    return null;
+  }
 
   private bindDepthBufferTexture(
     renderContext: PerspectiveViewRenderContext,