Meta Developers

To look at render stage profiling data, load a capture, go to the Event Browser, which can be opened by going to Window on the menu, and click the Meta

icon to perform a render stage trace. The headset proximity sensor will be briefly disabled so the trace can be performed without the need to cover it. Ensure that you connect to the device via the profiling mode. If you use normal replay mode/context, the Meta button for render stage trace will be grayed out.

After a few seconds, the render stage data appears in the Tile Timeline window. If the Tile Timeline window is not present, it can be found under the Window menu.

The Tile Timeline presents a lot of information in a compressed space. Zooming functionality is available with the mouse scrolling wheel to zoom in and out of areas of the timeline.

The top row of the timeline shows each of the surfaces rendered to in succession during the frame. Each block on the first row represents a surface and displays the following information:

Surface ID
Dimensions of the surface
MSAA status
Bit color and bit depth
Dimensions of the individual tiles that make up the surface
Total number of tiles for the surface

The second row of the timeline shows the active bin. To be precise, Render/StoreColor/LoadColor/StoreDS/LoadDS can belong to a bin and will have have an additional bin row above them if the surface is rendering with binning mode enabled.

The third row of the timeline lists all the render stages for each tile on a given surface. This provides accurate timings (in microseconds) for each render stage, with a color key and label indicating the specific render stage. Common render stages include the following:

Binning - The Meta Quest’s GPU uses a tiled architecture where all draw calls for a frame are executed in two stages. The first stage is the binning phase, where triangle vertex positions for all draw calls are calculated and assigned to bins that correspond to a partition of the drawing surface. A simplified version of vertex shaders are executed during binning for the purpose of finding a triangle’s position.
Render -This is the second stage of the draw call execution that began with binning. One chunk of this represents the total cost of all vertex and fragment operations for one bin. The full version of the vertex shaders are executed to compute the interpolants used by the fragment shader.
LoadColor - Loads the color from slow memory into fast memory. This can happen when starting to render into a surface without clearing it.
StoreColor - After an entire bin of pixel and fragment operations are done executing, the calculated color value is copied from fast memory (dedicated for the bin’s rendering operations) to slow memory.
LoadDS and StoreDS - These serve the same purpose as LoadColor and StoreColor, but for depth reads and writes to the surface.
Blit - This stage indicates copying between slow memory regions. This can happen for various operations, such as mipmap generation and when clearing a surface without rendering anything.
Preempt - The compositor is an OS-level service that executes at regular intervals to present the image submitted by the application to the screen. In order to deliver the image at the proper cadence, the GPU will preempt the application’s workload so that the compositor can complete its work on time.

Other render stages include the following:

GLAsyncCompute - For the OpenGL compute shader
VKQueue - For the Vulkan arbitrary start/stop within a queue stage
VKRenderClear - For the Vulkan render pass clear stage
VKWorkload - For the Vulkan workload (subpass) stage
VKAsyncCompute - For the Vulkan compute shader dispatch pass stage
VKLoadInput - For the Vulkan GMEM input attachment load stage

Surface Information

Left click on a surface time slice to see detailed information regarding the execution of the replay:

surface id
start timestamp - in microseconds
end timestamp - in microseconds
duration - in microseconds
width - width of the framebuffer
height - height of the framebuffer
msaa - multi-sampling anti-aliasing level
multiple rendertargets - number of rendertargets bound to the framebuffer
render mode
color bits per pixel
depth bits per pixel
stencil bits per pixel
color attachment attributes - Flags set for the color attachment
depth attachment attributes - Flags set for the depth attachment
stencil attachment attributes - Flags set for the stencil attachment
bin count - Number of bins this surface is divided into
bin width - Width of a single non-merged bin
bin height - Height of a single non-merged bin
stage count - Number of render stages executed under this surface
new frame surface - This will be 1 if the surface is the first surface in a frame. This is used to delimit one frame from another.
num rendered bins - Number of items in row 2 minus Binning, Blit or Compute
num surface stages - Number of items in row 3 plus Binning, Blit or Compute
compute only

Bin Information

Left click on a bin to see additional information on its execution.

# bins contained X/Y - If you’ve enabled Fixed Foveated Rendering, bins near the edge of the render texture will be combined. These values will be greater than 1 if this bin maps to multiple bins in the final render texture.
Fov Scale Factor X/Y [#] - If this bin maps to multiple bins in the final render texture, these values will indicate the FOV adjustments so the edges of this bin align with neighboring bins.

Stage Information

Left click on a render time slice to see the start and end timestamp, duration, and the type of render stage.

OpenGL Multiview

Due to hardware differences between the Meta Quest headsets, a render stage capture can appear different on an OpenGL app using multiview. The following timeline is from Meta Quest:

Note the two surfaces with the same ID. They are referring to the left eye and right eye slice of a 2D texture array. The same OpenGL app running on Meta Quest 2 will have only one single surface, but double the number of tiles:

Vulkan Multiview

Similar to OpenGL, a render stage capture can appear different on a Vulkan app using multiview. The following timeline is from Meta Quest:

Note the single surface with two binning stage (the yellow time slice). The same Vulkan app running on Meta Quest 2 will have only one single surface and one single binning stage due to hardware multiview:

Tile Browser

The Tile Browser tab shows your rendered frame broken up by each rendered bin, with a heatmap overlay that indicates which bins took longer than others. You can click on a bin to select it in the Tile Timeline. Both the Tile Browser and the Tile Timeline UI can be accessed under Window on the menu.