diff --git a/canvas-context.ts b/canvas-context.ts
index 036f40b..a643027 100644
--- a/canvas-context.ts
+++ b/canvas-context.ts
@@ -81,25 +81,31 @@ export class CanvasContext {
       this.tick = this.gl.frame(this.onBeforeFrame)
     }
   }
-  private onBeforeFrame = () => {
+
+  private onBeforeFrame = (context: regl.Context) => {
     this.gl.clear({ color: [0, 0, 0, 0] })
     this.tickNeeded = false
+
+    let beforeHandlers = performance.now()
     for (const handler of this.beforeFrameHandlers) {
       handler()
     }
+    let cpuTimeElapsed = performance.now() - beforeHandlers;
+
     if (this.tick && !this.tickNeeded) {
       this.tick.cancel()
       this.tick = null
     }
 
+    // TODO(jlfwong): It would be really nice to have GPU
+    // stats here, but I can't figure out how to interpret
+    // the gpuTime. I suspect this is caused by executing the same
+    // program multiple times without flushing.
+    // I'll investigate this at some point and report a bug to regl.
+
     console.group('Frame')
-    console.log('Rectangle Batch Renderer: ', this.rectangleBatchRenderer.stats().gpuTime.toFixed(3), 'in', this.rectangleBatchRenderer.stats().count, 'calls')
-    console.log('Texture Renderer: ', this.textureRenderer.stats().gpuTime.toFixed(3), 'in', this.textureRenderer.stats().count, 'calls')
-    console.log('Viewport Rect Renderer: ', this.viewportRectangleRenderer.stats().gpuTime.toFixed(3), 'in', this.viewportRectangleRenderer.stats().count, 'calls')
+    console.log('CPU Frame Generation Time (ms)', cpuTimeElapsed.toFixed(2))
     console.groupEnd()
-    this.rectangleBatchRenderer.resetStats()
-    this.textureRenderer.resetStats()
-    this.viewportRectangleRenderer.resetStats()
   }
 
   drawRectangleBatch(props: RectangleBatchRendererProps) {
diff --git a/flamechart-renderer.ts b/flamechart-renderer.ts
index 4b647f6..ad8cd05 100644
--- a/flamechart-renderer.ts
+++ b/flamechart-renderer.ts
@@ -1,16 +1,16 @@
-import { Flamechart, FlamechartFrame } from './flamechart'
+import { Flamechart } from './flamechart'
 import { RectangleBatch } from './rectangle-batch-renderer'
 import { CanvasContext } from './canvas-context';
 import { Vec2, Rect, AffineTransform } from './math'
 
-const MAX_BATCH_SIZE = 10000  // TODO(jlfwong): Bump this to 10000
+const MAX_BATCH_SIZE = 10000
 
 interface RangeTreeNode {
   getMinLeft(): number
   getMaxRight(): number
   getRectCount(): number
   getChildren(): RangeTreeNode[]
-  forEachBatch(cb: (batch: RectangleBatch) => void): void
+  forEachBatchInViewport(configSpaceViewport: Rect, cb: (batch: RectangleBatch) => void): void
 }
 
 class RangeTreeLeafNode implements RangeTreeNode {
@@ -20,13 +20,17 @@ class RangeTreeLeafNode implements RangeTreeNode {
     private batch: RectangleBatch,
     private minLeft: number,
     private maxRight: number
-  ) { }
+  ) {}
 
   getMinLeft() { return this.minLeft }
   getMaxRight() { return this.maxRight }
   getRectCount() { return this.batch.getRectCount() }
   getChildren() { return this.children }
-  forEachBatch(cb: (batch: RectangleBatch) => void) { cb(this.batch) }
+  forEachBatchInViewport(configSpaceViewport: Rect, cb: (batch: RectangleBatch) => void) {
+    if (this.maxRight < configSpaceViewport.left()) return
+    if (this.minLeft > configSpaceViewport.right()) return
+    cb(this.batch)
+  }
 }
 
 class RangeTreeInteriorNode implements RangeTreeNode {
@@ -44,9 +48,12 @@ class RangeTreeInteriorNode implements RangeTreeNode {
   getMaxRight() { return this.children[this.children.length - 1].getMaxRight() }
   getRectCount() { return this.rectCount }
   getChildren() { return this.children }
-  forEachBatch(cb: (batch: RectangleBatch) => void) {
+  forEachBatchInViewport(configSpaceViewport: Rect, cb: (batch: RectangleBatch) => void) {
+    // if (this.getMaxRight() < configSpaceViewport.left()) return
+    // if (this.getMinLeft() > configSpaceViewport.right()) return
+
     for (let child of this.children) {
-      child.forEachBatch(cb)
+      child.forEachBatchInViewport(configSpaceViewport, cb)
     }
   }
 }
@@ -58,7 +65,11 @@ export interface FlamechartRendererProps {
 
 class BoundedLayer {
   private rootNode: RangeTreeNode
-  constructor(private canvasContext: CanvasContext, flamechart: Flamechart, stackDepth: number) {
+  constructor(
+    private canvasContext: CanvasContext,
+    flamechart: Flamechart,
+    private stackDepth: number
+  ) {
     const leafNodes: RangeTreeLeafNode[] = []
 
     let minLeft = Infinity
@@ -76,6 +87,8 @@ class BoundedLayer {
         new Vec2(frame.start, stackDepth + 1),
         new Vec2(frame.end - frame.start, 1)
       )
+      minLeft = Math.min(minLeft, configSpaceBounds.left())
+      maxRight = Math.max(maxRight, configSpaceBounds.right())
       const color = flamechart.getColorForFrame(frame.node.frame)
       batch.addRect(configSpaceBounds, color)
     }
@@ -89,8 +102,26 @@ class BoundedLayer {
   }
 
   render(props: FlamechartRendererProps) {
-    // TODO(jlfwong): Cull batches!
-    this.rootNode.forEachBatch(batch => {
+    const configSpaceTop = this.stackDepth + 1
+    const configSpaceBottom = configSpaceTop + 1
+
+    const ndcToConfigSpace = props.configSpaceToNDC.inverted()
+    if (!ndcToConfigSpace) return
+    const configSpaceViewportRect = ndcToConfigSpace.transformRect(new Rect(
+      new Vec2(-1, -1), new Vec2(2, 2)
+    ))
+
+    if (configSpaceTop > configSpaceViewportRect.bottom()) {
+      // Entire layer is below the viewport
+      return
+    }
+
+    if (configSpaceBottom < configSpaceViewportRect.top()) {
+      // Entire layer is above the viewport
+      return
+    }
+
+    this.rootNode.forEachBatchInViewport(configSpaceViewportRect, batch => {
       this.canvasContext.drawRectangleBatch({ ...props, batch })
     })
   }
@@ -106,7 +137,6 @@ export class FlamechartRenderer {
   }
 
   render(props: FlamechartRendererProps) {
-    // TODO(jlfwong): Cull layers outside the viewport!
     for (let layer of this.layers) {
       layer.render(props)
     }
diff --git a/math.ts b/math.ts
index e0706fa..acd7886 100644
--- a/math.ts
+++ b/math.ts
@@ -18,6 +18,7 @@ export class Vec2 {
   equals(other: Vec2) { return this.x === other.x && this.y === other.y }
   length2() { return this.dot(this) }
   length() { return Math.sqrt(this.length2()) }
+  abs() { return new Vec2(Math.abs(this.x), Math.abs(this.y)) }
 
   static min(a: Vec2, b: Vec2) {
     return new Vec2(Math.min(a.x, b.x), Math.min(a.y, b.y))
@@ -171,10 +172,18 @@ export class AffineTransform {
   }
 
   transformRect(r: Rect) {
-    return new Rect(
-      this.transformPosition(r.origin),
-      this.transformVector(r.size)
-    )
+    const size = this.transformVector(r.size)
+    const origin = this.transformPosition(r.origin)
+
+    if (size.x < 0 && size.y < 0) {
+      return new Rect(origin.plus(size), size.abs())
+    } else if (size.x < 0) {
+      return new Rect(origin.withX(origin.x + size.x), size.abs())
+    } else if (size.y < 0) {
+      return new Rect(origin.withY(origin.y + size.y), size.abs())
+    }
+
+    return new Rect(origin, size)
   }
 
   flatten(): [number, number, number, number, number, number, number, number, number] {
diff --git a/regl.d.ts b/regl.d.ts
index 23c6d2b..83072c4 100644
--- a/regl.d.ts
+++ b/regl.d.ts
@@ -124,7 +124,7 @@ declare module "regl" {
 
       destroy(): void
 
-      frame(callback: (context?: Context) => void): Tick
+      frame(callback: (context: Context) => void): Tick
     }
 
     type TypedArray = Int8Array | Uint8Array | Uint8ClampedArray | Int16Array |