message: don't render while picking
diff: @@ -110,6 +110,7 @@ namespace Viewer {
  const groupPickTarget = createRenderTarget(ctx, pickWidth, pickHeight)
  let pickDirty = true
  + let isPicking = false
  let drawPending = false
  let lastRenderTime = -1
  const prevProjectionView = Mat4.zero()
  @@ -149,6 +150,7 @@ namespace Viewer {
  }
  function render(variant: RenderVariant, force?: boolean) {
  + if (isPicking) return false
  // const p = scene.boundingSphere.center
  // console.log(p[0], p[1], p[2])
  // Vec3.set(controls.target, p[0], p[1], p[2])
  @@ -226,6 +228,8 @@ namespace Viewer {
  function identify(x: number, y: number): PickingId | undefined {
  if (pickDirty) return undefined
  + isPicking = true
  +
  x *= ctx.pixelRatio
  y *= ctx.pixelRatio
  y = canvas.height - y // flip y
  @@ -246,6 +250,8 @@ namespace Viewer {
  ctx.readPixels(xp, yp, 1, 1, buffer)
  const groupId = decodeIdRGBA(buffer[0], buffer[1], buffer[2])
  + isPicking = false
  +
  return { objectId, instanceId, groupId }
  }
  