Merge pull request #240 from gerddie/master
Register EXT_depth_clamp for GLES
diff --git a/extensions/EXT/EXT_depth_clamp.txt b/extensions/EXT/EXT_depth_clamp.txt
new file mode 100644
index 0000000..e54d7b7
--- /dev/null
+++ b/extensions/EXT/EXT_depth_clamp.txt
@@ -0,0 +1,148 @@
+Name
+
+ EXT_depth_clamp
+
+Name Strings
+
+ GL_EXT_depth_clamp
+
+Contact
+
+ Gert Wollny (gert.wollny 'at' collabora.com)
+
+Notice
+
+ Copyright (c) 2019 Collabora LTD
+ Copyright (c) 2009-2013 The Khronos Group Inc. Copyright terms at
+ http://www.khronos.org/registry/speccopyright.html
+
+Status
+
+ FIXME
+
+Version
+
+ Version 1, 2019/01/24.
+ Based on ARB_depth_clamp version 4, modified 2009/08/02.
+
+Number
+
+ #309
+
+Dependencies
+
+ OpenGL ES 2.0 is required.
+ Written based on the wording of the OpenGL ES 3.2 specification.
+
+Overview
+
+ Conventional OpenGL clips geometric primitives to a clip volume
+ with six faces, two of which are the near and far clip planes.
+ Clipping to the near and far planes of the clip volume ensures that
+ interpolated depth values (after the depth range transform) must be
+ in the [0,1] range.
+
+ In some rendering applications such as shadow volumes, it is useful
+ to allow line and polygon primitives to be rasterized without
+ clipping the primitive to the near or far clip volume planes (side
+ clip volume planes clip normally). Without the near and far clip
+ planes, rasterization (pixel coverage determination) in X and Y
+ can proceed normally if we ignore the near and far clip planes.
+ The one major issue is that fragments of a primitive may extend
+ beyond the conventional window space depth range for depth values
+ (typically the range [0,1]). Rather than discarding fragments that
+ defy the window space depth range (effectively what near and far
+ plane clipping accomplish), the depth values can be clamped to the
+ current depth range.
+
+ This extension provides exactly such functionality. This
+ functionality is useful to obviate the need for near plane capping
+ of stenciled shadow volumes. The functionality may also be useful
+ for rendering geometry "beyond" the far plane if an alternative
+ algorithm (rather than depth testing) for hidden surface removal is
+ applied to such geometry (specifically, the painter's algorithm).
+ Similar situations at the near clip plane can be avoided at the
+ near clip plane where apparently solid objects can be "seen through"
+ if they intersect the near clip plane.
+
+New Procedures and Functions
+
+ None
+
+New Tokens
+
+ Accepted by the <cap> parameter of Enable, Disable, and IsEnabled,
+ and by the <pname> parameter of GetBooleanv, GetIntegerv,
+ GetFloatv:
+
+ DEPTH_CLAMP_EXT 0x864F
+
+Additions to Chapter 12 of the OpenGL ES 3.2 Specification (Fixed-Function Vertex Post-Processing)
+
+ -- Section 12.5 "Primitive Clipping"
+
+ Add to the end of the 1st paragraph:
+
+ "Depth clamping is enabled with the generic Enable command and
+ disabled with the Disable command. The value of the argument to
+ either command is DEPTH_CLAMP_EXT. If depth clamping is enabled, the
+ "-w_c <= z_c <= w_c" plane equation are ignored by view volume
+ clipping (effectively, there is no near or far plane clipping)."
+
+Additions to Chapter 15 of the OpenGL ES 3.2 Specification (Writing Fragments and Samples to the Framebuffer)
+
+ -- Section 15.1.3 "Depth buffer test"
+
+ Add to the end of the 2nd paragraph:
+
+ "If depth clamping (see section 12.15) is enabled, before the
+ incoming fragment's z_w is compared z_w is clamped to the range
+ [min(n,f),max(n,f)], where n and f are the current near and far
+ depth range values (see section 12.6.1)."
+
+Additions to the AGL/GLX/WGL Specifications
+
+ None
+
+GLX Protocol
+
+ None
+
+Errors
+
+ None
+
+New State
+
+Add to table 6.4, transformation state
+
+Get Value Type Get Command Initial Value Description Sec
+-------------- ---- ----------- ------------- -------------- ------
+DEPTH_CLAMP_EXT B IsEnabled False Depth clamping 12.5
+ on/off
+
+New Implementation Dependent State
+
+ None
+
+Issues
+
+ See the issue list in GL_ARB_depth_clamp.
+
+ Can fragments with w_c <=0 be generated when this extension is supported?
+
+ RESOLUTION: No. The inequalities in OpenGL ES Specification 12.5 clarify
+ that only primitives that lie in the region w_c >= 0 can be produced by
+ clipping and the vertex normalization in 12.6 clarifies that values
+ w_c = 0 are prohibited. Hence fragments with w_c <= 0 should also never
+ be generated when this extension is supported.
+
+ How does this extension differ from ARB_depth_clamp?
+
+ Instead of DEPTH_CLAMP the parameter is called DEPTH_CLAMP_EXT.
+ Push/pop attrib bits are not relevant for OpenGL ES.
+
+Revision History
+
+ Version 1, 2019/01/25 (Gert Wollny) - rewrite ARB_depth_clamp against
+ OpenGL ES 3.2 instead of OpenGL 3.1.
diff --git a/extensions/esext.php b/extensions/esext.php
index e4967a9..b9056e8 100644
--- a/extensions/esext.php
+++ b/extensions/esext.php
@@ -641,4 +641,6 @@
</li>
<li value=308><a href="extensions/NV/NV_compute_shader_derivatives.txt">GL_NV_compute_shader_derivatives</a>
</li>
+<li value=309><a href="extensions/EXT/EXT_depth_clamp.txt">GL_EXT_depth_clamp</a>
+</li>
</ol>
diff --git a/extensions/registry.py b/extensions/registry.py
index 5fd7989..c8f9d26 100644
--- a/extensions/registry.py
+++ b/extensions/registry.py
@@ -1714,6 +1714,11 @@
'supporters' : { 'NVIDIA' },
'url' : 'extensions/EXT/EXT_depth_bounds_test.txt',
},
+ 'GL_EXT_depth_clamp' : {
+ 'esnumber' : 309,
+ 'flags' : { 'public' },
+ 'url' : 'extensions/EXT/EXT_depth_clamp.txt',
+ },
'GL_EXT_direct_state_access' : {
'number' : 353,
'flags' : { 'public' },
diff --git a/xml/gl.xml b/xml/gl.xml
index d9475aa..b68f7a2 100644
--- a/xml/gl.xml
+++ b/xml/gl.xml
@@ -6629,6 +6629,7 @@
<enum value="0x864E" name="GL_DOT_PRODUCT_TEXTURE_RECTANGLE_NV"/>
<enum value="0x864F" name="GL_DEPTH_CLAMP"/>
<enum value="0x864F" name="GL_DEPTH_CLAMP_NV"/>
+ <enum value="0x864F" name="GL_DEPTH_CLAMP_EXT"/>
<enum value="0x8650" name="GL_VERTEX_ATTRIB_ARRAY0_NV"/>
<enum value="0x8651" name="GL_VERTEX_ATTRIB_ARRAY1_NV"/>
<enum value="0x8652" name="GL_VERTEX_ATTRIB_ARRAY2_NV"/>
@@ -43308,6 +43309,11 @@
<command name="glDepthBoundsEXT"/>
</require>
</extension>
+ <extension name="GL_EXT_depth_clamp" supported="gles2">
+ <require>
+ <enum name="GL_DEPTH_CLAMP_EXT"/>
+ </require>
+ </extension>
<extension name="GL_EXT_direct_state_access" supported="gl|glcore" comment="DSA extension doesn't identify which interfaces are core profile and keeps getting expanded. This is in sync with revision 34, 2010/09/07">
<require>
<enum name="GL_PROGRAM_MATRIX_EXT"/>
