US 20070182749 A1
Techniques to generate partial display updates in a buffered window system in which arbitrary visual effects are permitted to any one or more windows (e.g., application-specific window buffers) are described. Once a display output region is identified for updating, the buffered window system is interrogated to determine which regions within each window, if any, may effect the identified output region. Such determination considers the consequences any filters associated with a window impose on the region needed to make the output update.
1. A method to generate a display-wide visual effect, comprising:
copying an image buffer's contents into a second buffer;
causing the second buffer's contents to be filtered back into the image buffer through an application programming interface function to generate a specified visual effect, the second buffer associated with a system frame buffer, the application programming interface function using a graphics processing unit; and
compositing an application-specific window buffer into the image buffer, wherein the act of compositing is performed by the graphics processing unit after the act of filtering.
2. The method of
3. The method of
4. The method of
5. A method to generate a display-wide visual effect, comprising:
causing the contents of an application specific window buffer and an image buffer to be filtered into a second buffer through an application programming interface function to generate a specified visual effect, the application programming interface function using a graphics processing unit; and
transferring, using the graphics processing unit, contents of the second buffer into the image buffer, the image buffer associated with a system frame buffer.
6. The method of
7. The method of
8. A method to generate a display-wide visual effect, comprising:
compositing an application specific window buffer into an image buffer, the image buffer associated with a system frame buffer;
copying contents of the image buffer into a second buffer; and
causing the second buffer's contents to be filtered back into the image buffer through an application programming interface function to generate a specified visual effect, the application programming interface function using a graphics processing unit.
9. The method of
10. The method of
11. A computer-readable medium having computer-executable instructions stored therein for performing the method recited in any one of claims 1, 5 and 8.
12. A computer system, comprising:
a central processing unit;
memory, operatively coupled to the central processing unit, said memory adapted to provide a plurality of application-specific window buffers, at least one assembly buffer, and at least one frame buffer;
a display port operatively coupled to the frame buffer and adapted to couple to a display device;
a graphics processing unit, operatively coupled to the memory; and
one or more programs for causing the central processing unit and the graphics processing unit to perform the method recited in any of claims 1, 5 or 8.
This is a continuation application which claims priority to U.S. patent application Ser. No. 10/957,557 filed Oct. 1, 2004, which claims priority to U.S. patent application Ser. No. 10/877,358, entitled “Display-Wide Visual Effects for a Windowing System using a Programmable Graphics Processing Unit,” filed Jun. 25, 2004 and which is hereby incorporated by reference.
The invention relates generally to computer display technology and, more particularly, to the application of visual effects using a programmable graphics processing unit. The subject matter of the invention is generally related to the following jointly owned and co-pending patent applications: “System for Reducing the Number of Programs Necessary to Render an Image,” by John Harper, Ser. No. 10/826,773; “System for Optimizing Graphics Operations” by John Harper, Ralph Brunner, Peter Graffagnino, and Mark Zimmer, Ser. No. 10/825,694; “System for Emulating Graphics Operations,” by John Harper, Ser. No. 10/826,744; and “High-Level Program Interface for Graphics Operations,” by John Harper, Ralph Brunner, Peter Graffagnino, and Mark Zimmer, Ser. No. 10/826,762, each incorporated herein by reference in its entirety.
Because of the limited power of CPU 145, it has not been possible to provide more than rudimentary visual effects (e.g., translucency) at the system or display level. That is, while each application may effect substantially any desired visual effect or filter to their individual window buffer or backing store, it has not been possible to provide OS designers the ability to generate arbitrary visual effects at the screen or display level (e.g., by manipulation of assembly buffer 130 and/or frame buffer 135) without consuming virtually all of the system CPU's capability—which can lead to other problems such as poor user response and the like.
Thus, it would be beneficial to provide a mechanism by which a user (typically an OS-level programmer or designer) can systematically introduce arbitrary visual effects to windows as they are composited or to the final composited image prior to its display.
Methods, devices and systems in accordance with the invention provide a means for performing partial display updates in a windowing system that permits layer-specific filtering. One method in accordance with the invention includes: identifying an output region associated with a top-most display layer (e.g., an application-specific window buffer), wherein the output region has an associated output size and location; determining an input region for each of one or more filters, wherein each of the one or more filters is associated with a display layer and has an associated input size and location (substantially any known visual effect filter may be accommodated); establishing a buffer (e.g., an assembly buffer) having a size and location that corresponds to the union of the output region's location and each of the one or more input regions' locations; and compositing that portion of each display layer that overlaps the buffer's location into the established buffer. In one embodiment, that portion of the buffer corresponding to the identified output region is transferred to a frame buffer where it is used to update a user's display device. In another embodiment, the acts of identifying, determining and establishing are performed by one or more general purpose central processing units while the act of compositing is performed by one or more special purpose graphical processing units in a linear fashion (beginning with the bottom-most display layer and proceeding to the top-most display layer).
Methods and devices to generate partial display updates in a buffered window system in which arbitrary visual effects are permitted to any one or more windows are described. Once a display output region is identified for updating, the buffered window system is interrogated to determine which regions within each window, if any, may effect the identified output region. Such determination considers the consequences any filters associated with a window impose on the region needed to make the output update. The following embodiments of the invention, described in terms of the Mac OS X window server and compositing application, are illustrative only and are not to be considered limiting in any respect. (The Mac OS X operating system is developed, distributed and supported by Apple Computer, Inc. of Cupertino, Calif.)
As used herein, a “fragment program” is a collection of program statements designed to execute on a programmable GPU. Typically, fragment programs specify how to compute a single output pixel—many such fragments being run in parallel on the GPU to generate the final output image. Because many pixels are processed in parallel, GPUs can provide dramatically improved image processing capability (e.g., speed) over methods that rely only on a computer system's CPU (which is also responsible for performing other system and application duties).
Techniques in accordance with the invention provide four (4) types of visual effects at the system or display level. In the first, hereinafter referred to as “before-effects,” visual effects are applied to a buffered window system's assembly buffer prior to compositing a target window. In the second, hereinafter referred to as “on-effects,” visual effects are applied to a target window as it is being composited into the system's assembly buffer or a filter is used that operates on two inputs at once to generate a final image—one input being the target window, the other being the contents of the assembly buffer. In the third, hereinafter referred to as “above-effects,” visual effects are applied to a system's assembly buffer after compositing a target window. And in the fourth, hereinafter referred to as “full-screen effects,” visual effects are applied to the system's assembly buffer as it is transmitted to the system's frame-buffer for display.
It will be recognized that, as a practical matter, full-screen visual effects must conform to the system's frame buffer scan rate. That is, suitable visual effects in accordance with 700 include those effects in which GPU 230 generates filter output at a rate faster than (or at least as fast as) data is removed from frame buffer 245. If GPU output is generated slower than data is withdrawn from frame buffer 245, potential display problems can arise. Accordingly, full-screen effects are generally limited to those effects that can be applied at a rate faster than the frame buffer's output scan rate.
Event routing in a system employing visual effects in accordance with the invention must be modified to account for post-application effects. Referring to
It will be recognized by those of ordinary skill in the art that filters (i.e., fragment programs implementing a desired visual effect) operate by calculating a destination pixel location (i.e., xd, yd) based on one or more source pixels. Accordingly, the filters used to generate the effects may also be used to determine the source location (coordinates). Referring to
In addition to generating full-screen displays utilizing below, on and above filtering techniques as described herein, it is possible to generate partial screen updates. For example, if only a portion of a display has changed only that portion need be reconstituted in the display's frame buffer.
When layer-specific filters are used in accordance with the invention, the prior art approach of
To illustrate how process 1100 may be applied, consider
In accordance with process 1100, region 1230 is used to establish an initial AB size. (As would be known to those of ordinary skill in the art, the initial location of region 1230 is also recorded.) Next, region 1240 in layer L3 1220 needed by layer L4 1225's filter is determined. As shown, the filter associated with layer L4 1225 uses region 1240 from layer L3 1220 to compute or calculate its display (L4 Filter ROI 1235). It will be recognized that only that portion of layer L3 1220 that actually exists within region 1240 is used by layer L4 1225's filter. Because the extent of region 1240 is greater than that of initial region 1230, the AB extent is adjusted to include region 1240. A similar process is used to identify region 1250 in layer L2 1215. As shown in
The process described above, and outlined in blocks 1120-1130, is repeated again for layer L2 1215 to identify region 1260 in layer L1 1210. Note that region 1260 is smaller than region 1250 and so the size (extent) of the AB is not modified. Finally, region 1270 is determined based on layer L1's filter ROI 1265. If region 1270 covers some portion of background layer L0 1205 not yet “within” the determined AB, the extent of the AB is adjusted to do so. Thus, final AB size and location (extent) 1275 represents the union of the regions identified for each layer L0 1205 through L4 1225. With region 1275 known, an AB of the appropriate size may be instantiated and each layer that overlaps region 1275 is composited into it—starting at background layer L0 1205 and finishing with top-most layer L4 1225 (i.e., in a linear fashion). That portion of the AB corresponding to region 1230 may then be transferred into display 1200's frame buffer (at a location corresponding to region 1230) for display.
As noted above, visual effects and display updates in accordance with the invention may incorporate substantially any known visual effects. These include color effects, distortion effects, stylized effects, composition effects, half-tone effects, transition effects, tile effects, gradient effects, sharpen effects and blur effects.
Various changes in the components as well as in the details of the illustrated operational methods are possible without departing from the scope of the following claims. For instance, in the illustrative system of
The preceding description was presented to enable any person skilled in the art to make and use the invention as claimed and is provided in the context of the particular examples discussed above, variations of which will be readily apparent to those skilled in the art. Accordingly, the claims appended hereto are not intended to be limited by the disclosed embodiments, but are to be accorded their widest scope consistent with the principles and features disclosed herein.