| Name |
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| NV_scissor_exclusive |
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| Name Strings |
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| GL_NV_scissor_exclusive |
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| Contact |
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| Pat Brown, NVIDIA Corporation (pbrown 'at' nvidia.com) |
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| Contributors |
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| Mark Kilgard, NVIDIA |
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| Status |
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| Shipping |
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| Version |
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| Last Modified: September 15, 2018 |
| Revision: 1 |
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| Number |
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| OpenGL Extension #529 |
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| Dependencies |
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| This extension is written against the OpenGL 4.5 Specification |
| (Compatibility Profile), dated October 24, 2016. |
| |
| OpenGL 4.5 is required. |
| |
| This extension is written against the OpenGL Shading Language |
| Specification, version 4.50, dated April 14, 2016. |
| |
| This extension trivially interacts with EXT_draw_buffers2, |
| EXT_transform_feedback, NV_transform_feedback, and |
| EXT_direct_state_access. |
| |
| Overview |
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| In unextended OpenGL, applications can enable a per-viewport scissor test |
| (SCISSOR_TEST) where fragments are discarded if their (x,y) coordinates |
| lie outside the corresponding scissor rectangle. In this extension, we |
| provide a separate per-viewport exclusive scissor test, where fragments |
| are discarded if their (x,y) coordinates lie *inside* the corresponding |
| exclusive scissor rectangle. |
| |
| The regular (inclusive) scissor test and exclusive scissor test are |
| orthogonal; applications can enable either or both tests for each |
| viewport. If both tests are enabled, fragments will be discarded unless |
| their (x,y) coordinates are both inside the regular scissor rectangle and |
| outside the exclusive scissor rectangle. |
| |
| New Procedures and Functions |
| |
| void ScissorExclusiveArrayvNV(uint first, sizei count, const int *v); |
| void ScissorExclusiveNV(int x, int y, sizei width, sizei height); |
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| New Tokens |
| |
| Accepted by the <cap> parameter of Enable, Disable, and IsEnabled, by the |
| <target> parameter of Enablei, Disablei, IsEnabledi, EnableIndexedEXT, |
| DisableIndexedEXT, and IsEnabledIndexedEXT, and by the <pname> parameter |
| of GetBooleanv, GetIntegerv, GetInteger64v, GetFloatv, GetDoublev, |
| GetDoubleIndexedv, GetBooleani_v, GetIntegeri_v, GetInteger64i_v, |
| GetFloati_v, GetDoublei_v, GetBooleanIndexedvEXT, GetIntegerIndexedvEXT, |
| and GetFloatIndexedvEXT: |
| |
| SCISSOR_TEST_EXCLUSIVE_NV 0x9555 |
| |
| Accepted by the <pname> parameter of GetBooleanv, GetIntegerv, |
| GetInteger64v, GetFloatv, GetDoublev, GetBooleani_v, GetIntegeri_v, |
| GetInteger64i_v, GetFloati_v, GetDoublei_v, GetDoubleIndexedv, |
| GetBooleanIndexedvEXT, GetIntegerIndexedvEXT, and GetFloatIndexedvEXT: |
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| SCISSOR_BOX_EXCLUSIVE_NV 0x9556 |
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| Modifications to the OpenGL 4.5 Specification (Compatibility Profile) |
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| Insert a new section after section 14.9.2, Scissor Test (p. 560) |
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| 14.9.3 Exclusive Scissor Test |
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| Like the scissor test (section 14.9.2), the exclusive scissor test |
| determines if (x_w, y_w) lies outside the exclusive scissor rectangles |
| defined by four values for each viewport. These values are set with |
| |
| void ScissorExclusiveArrayvNV(uint first, sizei count, const int *v); |
| void ScissorExclusiveNV(int x, int y, sizei width, sizei height); |
| |
| ScissorExclusiveArrayvNV defines a set of exclusive scissor rectangles that |
| are each applied to the corresponding viewport (see section 13.6.1). |
| <first> specifies the index of the first exclusive scissor rectangle to |
| modify, and <count> specifies the number of scissor rectangles. <v> |
| specifies an array of 4*<count> integers, where each group of four |
| integers specifies the left column, bottom row, width, and height (in that |
| order) of an individual exclusive scissor rectangle. |
| |
| ScissorExclusiveNV is equivalent to calling ScissorExclusiveArrayvNV with |
| <first> set to 0, <count> set to the value of MAX_VIEWPORTS, and <v> |
| filled with an array of 4*MAX_VIEWPORTS integer, with each group of four |
| integers set to <x>, <y>, <width>, and <height>, respectively. |
| |
| When enabled, the exclusive scissor test passes only if the fragment is |
| outside the selected exclusive scissor rectangle, which is the case if |
| any of the following conditions is true: |
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| * x_w < left, |
| * x_w >= left + width, |
| * y_w < bottom, or |
| * y_w >= bottom + height. |
| |
| Otherwise, the test fails and the fragment is discarded. For points, |
| lines, and polygons, the scissor rectangle for a primitive is selected in |
| the same manner as the viewport (see section 13.6.1). For bitmaps, pixel |
| rectangles and buffer clears (see section 17.4.3), the scissor rectangle |
| numbered zero is used for the scissor test. |
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| Errors |
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| An INVALID_VALUE error is generated by ScissorExclusiveArrayvNV if |
| <first>+<count> is greater than the value of MAX_VIEWPORTS. |
| |
| An INVALID_VALUE error is generated if width or height is negative. |
| |
| The exclusive scissor test is enabled or disabled for all viewports using |
| Enable or Disable with target SCISSOR_TEST_EXCLUSIVE_NV. The test is enabled or |
| disabled for a specific viewport using Enablei or Disablei with the |
| constant SCISSOR_TEST_EXCLUSIVE_NV and the index of the selected viewport. |
| When disabled, it is as if the exclusive scissor test always passes. The |
| value of the scissor test enable for viewport <i> can be queried by |
| calling IsEnabledi with target SCISSOR_TEST_EXCLUSIVE_NV and index <i>. |
| The value of the exclusive scissor test enable for viewport zero may also |
| be queried by calling IsEnabled with the same target, but no index |
| parameter. |
| |
| Errors |
| |
| An INVALID_VALUE error is generated by Enablei, Disablei and |
| IsEnabledi if target is SCISSOR_TEST_EXCLUSIVE_NV and <index> is |
| greater than or equal to the value of MAX_VIEWPORTS. |
| |
| The state required for the exclusive scissor test consists of four integer |
| values per viewport, and a bit indicating whether the test is enabled or |
| disabled for each viewport. In the initial state for all viewports, the |
| exclusive scissor test is disabled and the exclusive scissor rectangle has |
| zero values for all of left, bottom, width, and height. |
| |
| Interactions with EXT_draw_buffers2 or EXT_transform_feedback or |
| NV_transform_feedback or EXT_direct_state_access |
| |
| Ignore references to GetBooleanIndexedvEXT or GetIntegerIndexedvEXT if |
| none of EXT_draw_buffers2, EXT_transform_feedback, NV_transform_feedback, |
| or EXT_direct_state_access are supported. |
| |
| Interactions with EXT_draw_buffers2 or EXT_direct_state_access |
| |
| Ignore references to EnableIndexedEXT, DisableIndexedEXT, and |
| IsEnabledIndexedEXT if neither of EXT_draw_buffers2 or |
| EXT_direct_state_access are supported. |
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| Interactions with EXT_direct_state_access |
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| Ignore references to GetFloatIndexedvEXT and GetDoubleIndexedvEXT if |
| EXT_direct_state_access is not supported. |
| |
| Additions to the AGL/GLX/WGL Specifications |
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| None |
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| Errors |
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| Errors are described in "Errors" sections of the spec language above. |
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| New State |
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| Get Value Type Get Command Initial Value Description Sec Attribute |
| ------------------------ ---------- ------------ ------------- ---------------------------- ----- --------- |
| SCISSOR_TEST_EXCLUSIVE_NV 16* x B IsEnabledi FALSE Exclusive scissoring enabled 14.9.3 scissor/enable |
| SCISSOR_BOX_EXCLUSIVE_NV 16* x 4 x Z GetIntegeri_v (0,0,0,0) Exclusive scissor rectangles 14.9.3 scissor |
| |
| New Implementation Dependent State |
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| None |
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| Issues |
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| (1) How should we name this extension? |
| |
| RESOLVED: NV_scissor_exclusive. It defines scissor rectangles and |
| tests that are "exclusive", where fragments pass only if they are |
| outside the rectangle. |
| |
| (2) What should we use for the default values for exclusive scissor |
| rectangles? |
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| RESOLVED: For inclusive scissors, the default values for an OpenGL |
| context are taken from the size of the drawable first used with the |
| context. While the inclusive scissor test is initially disabled, the |
| default state allows for "normal" unscissored rendering to that drawable |
| if the test is enabled without explicitly programming a scissor |
| rectangle. |
| |
| If we used similar state for exclusive scissors, enabling the exclusive |
| scissor test without programming a rectangle would scissor out all |
| rendering to such drawables. Instead, we specify the default rectangles |
| as (0,0,0,0), which would cause the exclusive scissor test to discard |
| nothing if enabled without programming a rectangle. Additionally, |
| this approach makes the default state independent of the drawable first |
| used with the OpenGL context. |
| |
| (3) How does the exclusive scissor interact with the functionality |
| of EXT_window_rectangles? |
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| RESOLVED: The exclusive scissor, as with the inclusive scissor, is orthogonal |
| to the window rectangles testing introduced by EXT_window_rectangles. |
| |
| The window rectangle testing applies to ALL viewports whereas the |
| exclusive scissor, as with the inclusive scissor, are selected by the |
| particular viewport index selected for rasterization. |
| |
| Additionally window rectangle testing is only support rendering |
| to framebuffer objects (FBOs) whereas the exclusive scissor, |
| as with the conventional inclusive scissor, works on all drawable. |
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| Revision History |
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| Revision 1 (pbrown) |
| - Internal revisions. |
