New Features for Intel GPA, Version 2.1

As good as the Intel GPA tool was for the development of the latest Ghostbusters game, several new features have been added subsequent to that project. Randel reports that he is finally enjoying a little downtime after working since 2006 on Ghostbusters, but he's already looking forward to the next project. "It will be really nice to have the new Intel GPA tools," he said recently. "There are still a few more things we can do to add those key details to a highly believable, fully destructible environment."

Here are some of the key new features that have been added to the Intel GPA to make it even easier to find and quickly address performance issues in games, as well as debug rendering problems:

Pixel History

Pixel history is a great new feature in Intel GPA that provides a wealth of information on any pixel in any render target. A zoom feature (using the mouse wheel) was also added for a more exact selection of a particular pixel of interest. To select a pixel, simply left-click a pixel in any render target. After a pixel is selected, the history of all GPU operations (draw calls, clears, and so on) that affected that pixel is displayed in the pixel history tab, which is automatically opened. This lets you see exactly which draw calls affected that pixel location for the render target from which it was selected. For each draw call in the list, the number of times the pixel was touched and the final pixel color are also displayed. If the pixel was rejected, for example if Z-test was enabled, the reason for the rejection is noted as well.

Pixel history enables two key use cases: visual debug and overdraw analysis. The visual debug workflow allows you to diagnose why a pixel was rendered incorrectly. It also shows which draw call in the history caused the selected pixel to be the color that it is. The overdraw analysis workflow depicts how much overdraw exists at any pixel location and specifically which draw calls contribute to it.

Overdraw Visualization per Render Target

The Intel GPA render target viewer has a new overdraw visualization mode. When enabled, each render target is visualized in gray scale. Overdraw corresponds to lighter pixels in the gray-scale visualization. By enabling this mode, you can immediately see which portions of the render target are being written to most often.

Intel GPA also allows you to combine the usage of both pixel history and overdraw visualization. This allows you to seamlessly find overdraw hotspots with the visualization and then immediately select any of the hot pixels to understand which draw calls are contributing to overdraw at that location.

Vertex Shader and Pixel Shader Durations

Shader durations are now enabled as metrics for all DirectX devices. These metrics are available in three places: the bar chart graph at the top of the user interface, the scene overview spreadsheet view on the left, and the details tab on the right.

With the bar chart, you can now select any metric in the x- and y-axis. For example, you can configure vertex shader duration in the x-axis and pixel shader duration in the y-axis. By looking at the shape of each rectangle in the bar chart you now can compare two metrics at the same time. Within the scene overview, you can view these new metrics in spreadsheet form by clicking the Customize button, and then selecting any metrics of your choice. Finally, the details tab always lists all possible metrics and enables you to view their values summed across the current draw call selection set.

Single Step Frame

Intel GPA has a new single step feature that enables better control over the frame to be captured and analyzed. When using the System Analyzer, simply press the pause button to pause the game in real time, then press the single step button as many times as needed to reach a frame of interest. The capture button can be pressed at any time.

In-Game Hot Key

The new hot-key feature allows easy frame captures on a single computer while playing the game. Simply launch the game using Intel GPA, run it full screen, and then press CTRL+SHIFT+C (or configure any keys you want to use) for each frame you want to capture. When you are ready to analyze, close the game, and then open the Frame Analyzer on the same computer or a remote system for analysis.

Export Metrics to a CSV File

With CSV (comma separated value) file export, detailed frame performance data can be saved and later pulled into Microsoft Excel or any other program that can process CSV files. This feature allows you to track game performance changes over time, compare game performance with various game options enabled, or even compare game performance on various graphics cards-all at a per-draw level of detail.

Because this feature is draw call selection set-based, you can select the draw calls you are interested in (or the whole frame) and export only those calls, so you don't have to wade through large amounts of data to find the details you want.

Conclusion

Intel GPA tools help game developers make sure that performance issues don't detract from a game's entertainment value. Developers can run code experiments that measure and report performance results in real time. Intel GPA provides open, accessible libraries that can both customize tools for specific needs and pull data for deeper analysis. Better use of screen real estate avoids the intrusive display overlay of other interfaces, and the ability to share captured frames with team members increases the efficiency of optimization.

Thanks to the Intel GPA tools, developers can learn more about what's going on "behind the curtain" on their games. The new features take an already strong engineering toolset and turn it into a formidable asset manager.

Thanks to interaction with game developers around the world, Intel continues to fine-tune these tools. Priced at USD 299, the Intel GPA tools are free to anyone willing to take the time to fully register. Go to www.intel.com/software/gpa and grab the tools and the documentation, read the case studies and white papers, and get involved in the developer forums. Your game's performance-and fun factor-are at stake.