diff --git a/CHANGES.md b/CHANGES.md
index 0afa5f0dbc3..538c9b575a8 100644
--- a/CHANGES.md
+++ b/CHANGES.md
@@ -9,6 +9,7 @@
 - Materials loaded from type now respect submaterials present in the referenced material type. [#10566](https://github.com/CesiumGS/cesium/issues/10566)
 - Reverts `createImageBitmap` options update to continue support for older browsers [#12846](https://github.com/CesiumGS/cesium/issues/12846)
 - Fix flickering artifact in Gaussian splat models caused by incorrect sorting results. [#12662](https://github.com/CesiumGS/cesium/issues/12662)
+- Fix rendering for geometry entities when `requestRenderMode` is enabled. [#12841](https://github.com/CesiumGS/cesium/pull/12841)
 - Improved performance and reduced memory usage of `Event` class. [#12896](https://github.com/CesiumGS/cesium/pull/12896)
 - Fixes vertical misalignment of glyphs in labels with small fonts [#8474](https://github.com/CesiumGS/cesium/issues/8474)
 - Prevent runtime errors for certain forms of invalid PNTS files [#12872](https://github.com/CesiumGS/cesium/issues/12872)
diff --git a/packages/engine/Source/Scene/Primitive.js b/packages/engine/Source/Scene/Primitive.js
index d2fab03f88d..6486bff22a8 100644
--- a/packages/engine/Source/Scene/Primitive.js
+++ b/packages/engine/Source/Scene/Primitive.js
@@ -2489,10 +2489,16 @@ Primitive.prototype.destroy = function () {
 function setReady(primitive, frameState, state, error) {
   primitive._error = error;
   primitive._state = state;
+
   frameState.afterRender.push(function () {
     primitive._ready =
       primitive._state === PrimitiveState.COMPLETE ||
       primitive._state === PrimitiveState.FAILED;
+
+    // Returning 'true' here will ensure that another rendering pass is
+    // triggered after the primitive actually became ready, to make sure
+    // that it is in fact rendered even in "request render mode"
+    return true;
   });
 }
 export default Primitive;
diff --git a/packages/engine/Source/Scene/PrimitiveState.js b/packages/engine/Source/Scene/PrimitiveState.js
index 08e862951b4..6420317b8f4 100644
--- a/packages/engine/Source/Scene/PrimitiveState.js
+++ b/packages/engine/Source/Scene/PrimitiveState.js
@@ -1,13 +1,136 @@
 /**
+ * The states that describe the lifecycle of a <code>Primitive</code>, as
+ * represented by the <code>primitive._state</code>.
+ *
+ * The state transitions are triggered by calls to the <code>update</code>
+ * function, but the actual state changes may happen asynchronously if the
+ * <code>asynchronous</code> flag of the primitive was set to
+ * <code>true</code>.
+ *
  * @private
  */
 const PrimitiveState = {
+  /**
+   * The initial state of a primitive.
+   *
+   * Note that this does NOT mean that the primitive is "ready", as indicated
+   * by the <code>_ready</code> property. It means the opposite: Nothing was
+   * done with the primitive at all.
+   *
+   * For primitives that are created with the <code>asynchronous:true</code>
+   * setting and that are in this state, the <code>update</code> call starts
+   * the creation of the geometry using web workers, and the primitive goes
+   * into the <code>CREATING</code> state.
+   *
+   * For synchronously created primitives, this state never matters. They will
+   * go into the COMBINED (or FAILED) state directly due to a call to the
+   * <code>update</code> function, if they are not yet FAILED, COMBINED,
+   * or COMPLETE.
+   */
   READY: 0,
+
+  /**
+   * The process of creating the primitive geometry is ongoing.
+   *
+   * A primitive can only ever be in this state when it was created
+   * with the <code>asynchronous:true</code> setting.
+   *
+   * It means that web workers are currently creating the geometry
+   * of the primitive.
+   *
+   * When the geometry creation succeeds, then the primitive will go
+   * into the CREATED state. Otherwise, it will go into the FAILED
+   * state. Both will happen asynchronously.
+   *
+   * The <code>update</code> function has to be called regularly
+   * until either of these states is reached.
+   */
   CREATING: 1,
+
+  /**
+   * The geometry for the primitive has been created.
+   *
+   * A primitive can only ever be in this state when it was created
+   * with the <code>asynchronous:true</code> setting.
+   *
+   * It means that web workers have (asynchronously) finished the
+   * creation of the geometry, but further (asynchronous) processing
+   * is necessary: If a primitive is determined to be in this state
+   * during a call to <code>update</code>, an asynchronous process
+   * is triggered to "combine" the geometry, meaning that the primitive
+   * will go into the COMBINING state.
+   */
   CREATED: 2,
+
+  /**
+   * The asynchronous creation of the geometry has been finished, but the
+   * asynchronous process of combining the geometry has not finished yet.
+   *
+   * A primitive can only ever be in this state when it was created
+   * with the <code>asynchronous:true</code> setting.
+   *
+   * It means that whatever is done with
+   * <code>PrimitivePipeline.packCombineGeometryParameters</code> has
+   * not finished yet. When combining the geometry succeeds, the
+   * primitive will go into the COMBINED state. Otherwise, it will
+   * go into the FAILED state.
+   */
   COMBINING: 3,
+
+  /**
+   * The geometry data is in a form that can be uploaded to the GPU.
+   *
+   * For <i>synchronous</i> primitives, this means that the geometry
+   * has been created (synchronously) due to the first call to the
+   * <code>update</code> function.
+   *
+   * For <i>asynchronous</i> primitives, this means that the asynchronous
+   * creation of the geometry and the asynchronous combination of the
+   * geometry have both finished.
+   *
+   * The <code>update</code> function has to be called regularly until
+   * this state is reached. When it is reached, the <code>update</code>
+   * call will cause the transition into the COMPLETE state.
+   */
   COMBINED: 4,
+
+  /**
+   * The geometry has been created and uploaded to the GPU.
+   *
+   * When this state is reached, it eventually causes the <code>_ready</code>
+   * flag of the primitive to become <code>true</code>.
+   *
+   * Note: Setting the <code>ready</code> flag does NOT happen in the
+   * <code>update</code> call: It only happens after rendering the next
+   * frame!
+   *
+   * Note: This state does not mean that nothing has to be done
+   * anymore (so the work is not "complete"). When the primitive is in
+   * this state, the <code>update</code> function still has to be
+   * called regularly.
+   */
   COMPLETE: 5,
+
+  /**
+   * The creation of the primitive failed.
+   *
+   * When this state is reached, it eventually causes the <code>_ready</code>
+   * flag of the primitive to become <code>true</code>.
+   *
+   * Note: Setting the <code>ready</code> flag does NOT happen in the
+   * <code>update</code> call: It only happens after rendering the next
+   * frame!
+   *
+   * This state can be reached when the (synchronous or asynchronous)
+   * creation of the geometry, or the (asynchronous) combination of
+   * the geometry caused any form of error.
+   *
+   * It may or may not imply the presence of the <code>_error</code> property.
+   * When the <code>_error</code> property is present on a FAILED primitive,
+   * this error will be thrown during the <code>update</code> call. When it
+   * is not present for a FAILED primitive, then the <code>update</code> call
+   * will do nothing.
+   */
   FAILED: 6,
 };
 export default Object.freeze(PrimitiveState);