Class NVCoverageSample
Anti-aliasing is a critical component for delivering high-quality OpenGL rendering. Traditionally, OpenGL implementations have implemented two anti-aliasing algorithms: edge anti-aliasing and multisampling.
Edge anti-aliasing computes fractional fragment coverage for all primitives in a rendered frame, and blends edges of abutting and/or overlapping primitives to produce smooth results. The image quality produced by this approach is exceptionally high; however, applications are render their geometry perfectly ordered back-to-front in order to avoid artifacts such as bleed-through. Given the algorithmic complexity and performance cost of performing exact geometric sorts, edge anti-aliasing has been used very sparingly, and almost never in interactive games.
Multisampling, on the other hand, computes and stores subpixel (a.k.a. "sample") coverage for rasterized fragments, and replicates all post-alpha test operations (e.g., depth test, stencil test, alpha blend) for each sample. After the entire scene is rendered, the samples are filtered to compute the final anti-aliased image. Because the post-alpha test operations are replicated for each sample, all of the bleed-through and ordering artifacts that could occur with edge anti-aliasing are avoided completely; however, since each sample must be computed and stored separately, anti-aliasing quality is limited by framebuffer storage and rendering performance.
This extension introduces a new anti-aliasing algorithm to OpenGL, which dramatically improves multisampling quality without adversely affecting multisampling's robustness or significantly increasing the storage required, coverage sampling.
Coverage sampling adds an additional high-precision geometric coverage buffer to the framebuffer, which is used to produce high-quality filtered results (with or without the presence of a multisample buffer). This coverage information is computed and stored during rasterization; since applications may render objects where the specified geometry does not correspond to the visual result (examples include alpha-testing for "imposters," or extruded volume rendering for stencil shadow volumes), coverage buffer updates may be masked by the application, analagous to masking the depth buffer.
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Field Summary
FieldsModifier and TypeFieldDescriptionstatic final int
Accepted by theoperation
parameter of CoverageOperationNV.static final int
Accepted by theattachment
parameter of FramebufferRenderbuffer, and GetFramebufferAttachmentParameteriv.static final int
Accepted by theoperation
parameter of CoverageOperationNV.static final int
Accepted by thebuf
parameter of Clear.static final int
Accepted by thepname
parameter of GetIntegerv.static final int
Accepted by theinternalformat
parameter of RenderbufferStorageEXT and theformat
parameter of ReadPixels.static final int
Accepted by theinternalformat
parameter of RenderbufferStorageEXT.static final int
Accepted by theoperation
parameter of CoverageOperationNV.static final int
Accepted by thepname
parameter of GetIntegerv. -
Method Summary
Modifier and TypeMethodDescriptionstatic void
glCoverageMaskNV
(boolean mask) static void
glCoverageOperationNV
(int operation)
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Field Details
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GL_COVERAGE_COMPONENT_NV
public static final int GL_COVERAGE_COMPONENT_NVAccepted by theinternalformat
parameter of RenderbufferStorageEXT and theformat
parameter of ReadPixels.- See Also:
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GL_COVERAGE_COMPONENT4_NV
public static final int GL_COVERAGE_COMPONENT4_NVAccepted by theinternalformat
parameter of RenderbufferStorageEXT.- See Also:
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GL_COVERAGE_ALL_FRAGMENTS_NV
public static final int GL_COVERAGE_ALL_FRAGMENTS_NVAccepted by theoperation
parameter of CoverageOperationNV.- See Also:
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GL_COVERAGE_EDGE_FRAGMENTS_NV
public static final int GL_COVERAGE_EDGE_FRAGMENTS_NVAccepted by theoperation
parameter of CoverageOperationNV.- See Also:
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GL_COVERAGE_AUTOMATIC_NV
public static final int GL_COVERAGE_AUTOMATIC_NVAccepted by theoperation
parameter of CoverageOperationNV.- See Also:
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GL_COVERAGE_ATTACHMENT_NV
public static final int GL_COVERAGE_ATTACHMENT_NVAccepted by theattachment
parameter of FramebufferRenderbuffer, and GetFramebufferAttachmentParameteriv.- See Also:
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GL_COVERAGE_BUFFER_BIT_NV
public static final int GL_COVERAGE_BUFFER_BIT_NVAccepted by thebuf
parameter of Clear.- See Also:
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GL_COVERAGE_BUFFERS_NV
public static final int GL_COVERAGE_BUFFERS_NVAccepted by thepname
parameter of GetIntegerv.- See Also:
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GL_COVERAGE_SAMPLES_NV
public static final int GL_COVERAGE_SAMPLES_NVAccepted by thepname
parameter of GetIntegerv.- See Also:
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Method Details
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glCoverageMaskNV
public static void glCoverageMaskNV(boolean mask) -
glCoverageOperationNV
public static void glCoverageOperationNV(int operation)
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