| Name |
| |
| NV_framebuffer_multisample_coverage |
| |
| Name Strings |
| |
| GL_NV_framebuffer_multisample_coverage |
| |
| Contact |
| |
| Mike Strauss, NVIDIA Corporation (mstrauss 'at' nvidia.com) |
| |
| Status |
| |
| Shipping in NVIDIA Release 95 drivers (November 2006) |
| |
| Functionality supported by GeForce 8800 |
| |
| Version |
| |
| Last Modified Date: May 31, 2008 |
| Revision #9 |
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| Number |
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| 336 |
| |
| Dependencies |
| |
| Requires GL_EXT_framebuffer_object. |
| |
| Requires GL_EXT_framebuffer_blit. |
| |
| Requires GL_EXT_framebuffer_multisample. |
| |
| Written based on the wording of the OpenGL 1.5 specification. |
| |
| Overview |
| |
| This extension extends the EXT_framebuffer_multisample |
| specification by providing a new function, |
| RenderBufferStorageMultisampleCoverageNV, that distinguishes |
| between color samples and coverage samples. |
| |
| EXT_framebuffer_multisample introduced the function |
| RenderbufferStorageMultisampleEXT as a method of defining the |
| storage parameters for a multisample render buffer. This function |
| takes a <samples> parameter. Using rules provided by the |
| specification, the <samples> parameter is resolved to an actual |
| number of samples that is supported by the underlying hardware. |
| EXT_framebuffer_multisample does not specify whether <samples> |
| refers to coverage samples or color samples. |
| |
| This extension adds the function |
| RenderbufferStorageMultisamplCoverageNV, which takes a |
| <coverageSamples> parameter as well as a <colorSamples> parameter. |
| These two parameters give developers more fine grained control over |
| the quality of multisampled images. |
| |
| IP Status |
| |
| No known IP issues. |
| |
| New Procedures and Functions |
| |
| void RenderbufferStorageMultisampleCoverageNV( |
| enum target, sizei coverageSamples, |
| sizei colorSamples, enum internalformat, |
| sizei width, sizei height); |
| |
| New Tokens |
| |
| Accepted by the <pname> parameter of GetRenderbufferParameterivEXT: |
| |
| RENDERBUFFER_COVERAGE_SAMPLES_NV 0x8CAB |
| RENDERBUFFER_COLOR_SAMPLES_NV 0x8E10 |
| |
| |
| Accepted by the <pname> parameter of GetIntegerv: |
| |
| MAX_MULTISAMPLE_COVERAGE_MODES_NV 0x8E11 |
| MULTISAMPLE_COVERAGE_MODES_NV 0x8E12 |
| |
| Additions to Chapter 2 of the OpenGL 2.0 Specification (OpenGL Operation) |
| |
| None. |
| |
| Additions to Chapter 3 of the OpenGL 2.0 Specification (Rasterization) |
| |
| None. |
| |
| Additions to Chapter 4 of the OpenGL 2.0 Specification (Per-Fragment |
| Operations and the Frame Buffer) |
| |
| Modification to 4.4.2.1 (Renderbuffer Objects) |
| |
| Add, just above the definition of RenderbufferStorageMultisampleEXT: |
| |
| "The command |
| |
| void RenderbufferStorageMultisampleCoverageNV( |
| enum target, sizei coverageSamples, |
| sizei colorSamples, enum internalformat, |
| sizei width, sizei height); |
| |
| establishes the data storage, format, dimensions, number of coverage |
| samples, and number of color samples of a renderbuffer object's |
| image. <target> must be RENDERBUFFER_EXT. <internalformat> must be |
| RGB, RGBA, DEPTH_COMPONENT, STENCIL_INDEX, or one of the internal |
| formats from table 3.16 or table 2.nnn that has a base internal |
| format of RGB, RGBA, DEPTH_COMPONENT, or STENCIL_INDEX. <width> |
| and <height> are the dimensions in pixels of the renderbuffer. If |
| either <width> or <height> is greater than |
| MAX_RENDERBUFFER_SIZE_EXT, the error INVALID_VALUE is generated. If |
| the GL is unable to create a data store of the requested size, the |
| error OUT_OF_MEMORY is generated. |
| |
| Upon success, RenderbufferStorageMultisampleCoverageNV deletes any |
| existing data store for the renderbuffer image and the contents of |
| the data store after calling |
| RenderbufferStorageMultisampleCoverageNV are undefined. |
| RENDERBUFFER_WIDTH_EXT is set to <width>, RENDERBUFFER_HEIGHT_EXT |
| is set to <height>, and RENDERBUFFER_INTERNAL_FORMAT_EXT is set to |
| <internalformat>. |
| |
| If <coverageSamples> is zero, then RENDERBUFFER_COVERAGE_SAMPLES_NV |
| is set to zero. Otherwise <coverageSamples> represents a request |
| for a desired minimum number of coverage samples. Since different |
| implementations may support different coverage sample counts for |
| multisampled rendering, the actual number of coverage samples |
| allocated for the renderbuffer image is implementation dependent. |
| However, the resulting value for RENDERBUFFER_COVERAGE_SAMPLES_NV is |
| guaranteed to be greater than or equal to <coverageSamples> and no |
| more than the next larger coverage sample count supported by the |
| implementation. |
| |
| If <colorSamples> is zero then RENDERBUFFER_COLOR_SAMPLES_NV is set |
| to zero. Otherwise, <colorSamples> represents a request for a |
| desired minimum number of colors samples. Since different |
| implementations may support different color sample counts for |
| multisampled rendering, the actual number of color samples |
| allocated for the renderbuffer image is implementation dependent. |
| Furthermore, a given implementation may support different color |
| sample counts for each supported coverage sample count. The |
| resulting value for RENDERBUFFER_COLOR_SAMPLES_NV is determined |
| after resolving the value for RENDERBUFFER_COVERAGE_SAMPLES_NV. |
| If the requested color sample count exceeds the maximum number of |
| color samples supported by the implementation given the value of |
| RENDERBUFFER_COVERAGE_SAMPLES_NV, the implementation will set |
| RENDERBUFFER_COLOR_SAMPLES_NV to the highest supported value. |
| Otherwise, the resulting value for RENDERBUFFER_COLOR_SAMPLES_NV is |
| guaranteed to be greater than or equal to <colorSamples> and no |
| more than the next larger color sample count supported by the |
| implementation given the value of RENDERBUFFER_COVERAGE_SAMPLES_NV. |
| |
| If <colorSamples> is greater than <coverageSamples>, the error |
| INVALID_VALUE is generated. |
| |
| If <coverageSamples> or <colorSamples> is greater than |
| MAX_SAMPLES_EXT, the error INVALID_VALUE is generated. |
| |
| If <coverageSamples> is greater than zero, and <colorSamples> is |
| zero, RENDERBUFFER_COLOR_SAMPLES_NV is set to an implementation |
| dependent value based on RENDERBUFFER_COVERAGE_SAMPLES_NV. |
| |
| An implementation may only support a subset of the possible |
| combinations of coverage samples and color samples. Requests for |
| combinations not supported by the implementation are resolved to |
| a supported combination using the rules above. The number of |
| supported combinations is MAX_MULTISAMPLE_COVERAGE_MODES_NV. |
| MULTISAMPLE_COVERAGE_MODES_NV is an array of |
| MAX_MULTISAMPLE_COVERAGE_MODES_NV pairs of integers representing |
| the combinations of coverage samples and color samples supported |
| by the implementation. The first integer in each pair corresponds |
| to coverage samples, while the second corresponds to color samples. |
| |
| Modify the definition of RenderbufferStorageMultisampleEXT as |
| follows: |
| |
| "The command |
| |
| void RenderbufferStorageMultisampleEXT( |
| enum target, sizei samples, |
| enum internalformat, |
| sizei width, sizei height); |
| |
| is equivalent to calling |
| |
| RenderbufferStorageMultisampleCoverageNV(target, samples, 0, |
| internalforamt, width, height). |
| |
| Modification to 4.4.4.2 (Framebuffer Completeness) |
| |
| Modify the RENDERBUFFER_SAMPLES_EXT entry in the bullet list: |
| |
| * The value of RENDERBUFFER_COVERAGE_SAMPLES_NV is the same for all |
| attached images. |
| { FRAMEBUFFER_INCOMPLETE_MULTISAMPLE } |
| |
| Add an entry to the bullet list: |
| |
| * The value of RENDERBUFFER_COLOR_SAMPLES_NV is the same for all |
| attached images. |
| { FRAMEBUFFER_INCOMPLETE_MULTISAMPLE_EXT } |
| |
| Additions to Chapter 5 of the OpenGL 2.0 Specification (Special Functions) |
| |
| None. |
| |
| Additions to Chapter 6 of the OpenGL 2.0 Specification (State and |
| State Requests) |
| |
| None. |
| |
| Additions to Appendix A of the OpenGL 2.0 Specification (Invariance) |
| |
| None. |
| |
| Errors |
| |
| The error INVALID_OPERATION is generated if |
| RenderbufferStorageMultisampleCoverageNV is called and |
| <colorSamples> is greater than <coverageSamples> |
| |
| The error INVALID_VALUE is generated if |
| RenderbufferStorageMultisampleCoverageNV is called and |
| <coverageSamples> is greater than MAX_SAMPLES_EXT. |
| |
| The error INVALID_VALUE is generated if |
| RenderbufferStorageMultisampleCoverageNV is called and |
| <colorSamples> is greater than MAX_SAMPLES_EXT. |
| |
| New State |
| |
| (add to table 8.nnn, "Renderbuffers (state per renderbuffer object)") |
| |
| Initial |
| Get Value Type Get Command Value Description Section Attribute |
| -------------------------------- ---- ----------------------------- ------- ------------------- ------------ --------- |
| RENDERBUFFER_COVERAGE_SAMPLES_NV Z+ GetRenderbufferParameterivEXT 0 Number of coverage 4.4.2.1 - |
| samples used by the |
| renderbuffer |
| RENDERBUFFER_COLOR_SAMPLES_NV Z+ GetRenderbufferParameterivEXT 0 Number of color 4.4.2.1 - |
| samples used by the |
| renderbuffer |
| |
| (modify RENDERBUFFER_SAMPLES_EXT entry in table 8.nnn) |
| |
| Initial |
| Get Value Type Get Command Value Description Section Attribute |
| ------------------------ ---- ----------------------------- ------ ------------------- ------------ --------- |
| RENDERBUFFER_SAMPLES_EXT Z+ GetRenderbufferParameterivEXT 0 Alias for 4.4.2.1 - |
| RENDERBUFFER_- |
| COVERAGE_SAMPLES_NV |
| |
| New Implementation Dependent State |
| |
| Minimum |
| Get Value Type Get Command Value Description Section Attribute |
| --------------------------------- --------- ----------- ------- ------------------------------------ ------- --------- |
| MAX_MULTISAMPLE_COVERAGE_MODES_NV Z+ GetIntegerv 0 Number of unique combinations of 4.4.2.1 - |
| <coverageSamples> and <colorSamples> |
| supported by the implementation. |
| MULTISAMPLE_COVERAGE_MODES_NV n * 2 x Z+ GetIntegerv - MAX_MULTISAMPLE_COVERAGE_MODES_NV (n) 4.4.2.1 - |
| pairs of integers. Each pair is |
| a unique combination of |
| <coverageSamples> and <colorSamples> |
| supported by the implementation. |
| |
| Issues |
| |
| (1) How should RenderbufferStorageMultisampleEXT be layered on top |
| of RenderbufferStorageMultisampleCoverageNV? |
| |
| RESOLVED. NVIDIA will expose this extension at the same time |
| that EXT_framebuffer_multisample is exposed, so there will not |
| be any issues with backward compatibility. However, some |
| developers choose not to use vendor specific extensions. These |
| developers should be able to make use of current and future |
| hardware that differentiates between color and coverage |
| samples. Since color samples are a subset of coverage samples, |
| the <samples> parameter to RenderbufferStorageMultisampleEXT |
| should be treated as a request for coverage samples. The |
| implementation is free to choose the number of color samples |
| used by the renderbuffer. |
| |
| (2) <coverageSamples> is rounded up to the next highest |
| number of samples supported by the implementation. How |
| should <colorSamples> be rounded given that an implementation |
| may not support all combinations of <coverageSamples> and |
| <colorSamples>? |
| |
| RESOLVED: It is a requirement that <coverageSamples> be |
| compatible with the <samples> parameter to |
| RenderbufferStorageMultisampleEXT. While it is desirable for |
| <colorSamples> to resolve the same way as <coverageSamples>, |
| this may not always be possible. An implementation may support |
| a different maximum number of color samples for each coverage |
| sample count. It would be confusing to set an error when |
| <colorSamples> exceeds the maximum supported number of color |
| samples for a given coverage sample count, because there |
| is no mechanism to query or predict this behavior. Therefore, |
| the implementation should round <colorSamples> down when it |
| exceeds the maximum number of color samples supported with the |
| given coverage sample count. Otherwise, <colorSamples> is |
| rounded up to the next highest number of color samples |
| supported by the implementation. |
| |
| (3) EXT_framebuffer_multisample provides a way to query the maximum |
| number of samples supported by an implementation. Should a new |
| query mechanism be added so that an application can determine |
| the maximum number of color samples supported with a given |
| number of coverage samples? |
| |
| RESOLVED: Yes. An application can use GetIntegerv to query |
| MAX_MULTISAMPLE_COVERAGE_MODES_NV. The result is the number of |
| unique combinations of <coverageSamples> and <colorSamples> that |
| are supported by the implementation. GetIntegerv can be used |
| with MULTISAMPLE_COVERAGE_MODES_NV to query these combinations. |
| The integer array is populated with |
| MAX_MULTISAMPLE_COVERAGE_MODES_NV pairs of integers, where each |
| pair describes a unique multisample coverage mode. The first |
| integer in each pair is the number of coverage samples and the |
| second integer is the number of color samples. An example is |
| below: |
| |
| // Get the number of unique multisample coverage modes |
| glGetIntegerv(GL_MAX_MULTISAMPLE_COVERAGE_MODES_NV, &numModes); |
| |
| // Allocate enough memory to store the array of modes |
| GLint *modes = (GLint*)malloc(2*numModes*sizeof(GLint)); |
| |
| // Get the list of modes |
| glGetIntegerv(GL_MULTISAMPLE_COVERAGE_MODES_NV, modes); |
| |
| // Print out all of the modes |
| for (i = 0; i < numModes; i++) { |
| printf("%d coverage samples, %d color samples\n", |
| modes[i*2+0], // coverage samples for mode i |
| modes[i*2+1]); // color samples for mode i |
| } |
| |
| Revision History |
| |
| Rev. Date Author Changes |
| ---- -------- -------- -------------------------------------------- |
| 7-9 05/31/08 mjk Miscellaneous typo fixes. |
| |
| 6 mstrauss Internal spec development. |
