1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
|
<?xml version="1.0"?>
<draft href="WEBGL_multiview/">
<name>WEBGL_multiview</name>
<contact>
<a href="https://www.khronos.org/webgl/public-mailing-list/">WebGL working group</a> (public_webgl 'at' khronos.org)
</contact>
<contributors>
<contributor>Olli Etuaho, NVIDIA</contributor>
<contributor>Members of the WebGL working group</contributor>
</contributors>
<number>36</number>
<depends>
<api version="1.0"/>
</depends>
<overview>
<mirrors href="https://www.opengl.org/registry/specs/OVR/multiview.txt" name="OVR_multiview">
<addendum>
Calling <code>framebufferTextureMultiviewWEBGL</code> with a non-null <code>texture</code> parameter that does not identify a 2D array texture generates an <code>INVALID_OPERATION</code> error.
</addendum>
<addendum>
The values of <code>baseViewIndex</code> and <code>numViews</code> can result in an error only if the <code>texture</code> parameter is non-null.
</addendum>
<addendum>
If <code>baseViewIndex</code> is not the same for all framebuffer attachment points where the value of <code>FRAMEBUFFER_ATTACHMENT_OBJECT_TYPE</code> is not <code>NONE</code> the framebuffer is considered incomplete. Calling <code>getFramebufferStatus</code> for a framebuffer in this state returns <code>FRAMEBUFFER_INCOMPLETE_VIEW_TARGETS_OVR</code>. Other rules for framebuffer completeness from the OVR_multiview specification also apply.
</addendum>
<addendum>
Other web APIs may expose <i>opaque multiview framebuffers</i>. Opaque multiview framebuffers are <code>WebGLFramebuffer</code> objects that act as if they have multi-view attachments, but their attachments are not exposed as textures or renderbuffers and can not be changed. Opaque multiview framebuffers may have any combination of color, depth and stencil attachments.
</addendum>
<addendum>
Calling <code>framebufferRenderbuffer</code>, <code>framebufferTexture2D</code>, <code>framebufferTextureLayer</code>, <code>framebufferTextureMultiviewWEBGL</code>, or any other call that could change framebuffer attachments with an opaque multiview framebuffer bound to <code>target</code> generates an <code>INVALID_OPERATION</code> error.
</addendum>
<addendum>
If an opaque framebuffer is bound to <code>target</code> when calling <code>getFramebufferAttachmentParameter</code>, then <code>attachment</code> must be <code>BACK</code>, <code>DEPTH</code>, or <code>STENCIL</code>.
</addendum>
<addendum>
If an opaque framebuffer is bound to <code>target</code> when calling <code>getFramebufferAttachmentParameter</code>, then <code>pname</code> must not be <code>FRAMEBUFFER_ATTACHMENT_OBJECT_NAME</code>.
</addendum>
<addendum>
Querying <code>FRAMEBUFFER_ATTACHMENT_TEXTURE_NUM_VIEWS_OVR</code> on an opaque multiview framebuffer attachment point that has attachments must return the number of views in the opaque multiview framebuffer.
</addendum>
<addendum>
Querying <code>FRAMEBUFFER_ATTACHMENT_TEXTURE_BASE_VIEW_INDEX_OVR</code> on an opaque multiview framebuffer must return 0.
</addendum>
<addendum>
Querying <code>FRAMEBUFFER_ATTACHMENT_OBJECT_TYPE</code> on an opaque multiview framebuffer must return <code>FRAMEBUFFER_DEFAULT</code>.
</addendum>
<addendum>
The number of views in an opaque multiview framebuffer may be greater than the maximum number of texture array views (the value of <code>MAX_VIEWS_OVR</code>).
</addendum>
<addendum>
Passing an opaque multiview framebuffer to <code>deleteFramebuffer</code> generates an <code>INVALID_OPERATION</code> error.
</addendum>
<addendum>
Although the extension name is prefixed with WEBGL the extension must be enabled with the
<code>#extension GL_OVR_multiview</code> directive, as shown in the sample code, to use
the extension in a shader.
Likewise the shading language preprocessor <code>#define GL_OVR_multiview</code>, will be defined to 1 if the extension is supported.
</addendum>
<addendum>
This extension relaxes the restriction in OVR_multiview that only <code>gl_Position</code> can depend on ViewID in the vertex shader. With this change, view-dependent outputs like reflection vectors and similar are allowed.
</addendum>
<addendum>
When the number of views specified in the active program is one, <code>gl_ViewID_OVR</code> will always evaluate to zero.
</addendum>
<addendum>
When a shader written in OpenGL ES shading language version 1.00 enables or requires <code>GL_OVR_multiview</code> with an extension directive, <code>layout</code> is treated as a keyword rather than an identifier, and using a layout qualifier to specify <code>num_views</code> is allowed. Other uses of layout qualifiers are not allowed in OpenGL ES shading language 1.00.
</addendum>
<addendum>
In OpenGL ES shading language version 1.00 <code>gl_ViewID_OVR</code> has the type <code>int</code> as opposed to <code>uint</code>.
</addendum>
<addendum>
When a timer query is active and the number of views in the current draw framebuffer is greater than one, attempting to draw or calling <code>clear</code> generates an <code>INVALID_OPERATION</code> error.
</addendum>
<addendum>
When the number of views in the current draw framebuffer is greater than one and the active program does not declare a number of views, attempting to draw generates an <code>INVALID_OPERATION</code> error.
</addendum>
</mirrors>
<features>
<feature>
Adds support for rendering into multiple views simultaneously. This is supported for opaque multiview framebuffers starting from WebGL 1.0, and 2D texture arrays starting from WebGL 2.0.
</feature>
<feature>
When a shader enables, requires, or warns <code>GL_OVR_multiview</code> with an extension directive:
<ul>
<li><code>gl_ViewID_OVR</code> is a built-in input of the type uint.</li>
</ul>
</feature>
<feature>
The GLSL macro <code>GL_OVR_multiview</code> is defined as 1.
</feature>
</features>
</overview>
<idl xml:space="preserve">
[NoInterfaceObject]
interface WEBGL_multiview {
const GLenum FRAMEBUFFER_ATTACHMENT_TEXTURE_NUM_VIEWS_OVR = 0x9630;
const GLenum FRAMEBUFFER_ATTACHMENT_TEXTURE_BASE_VIEW_INDEX_OVR = 0x9632;
const GLenum MAX_VIEWS_OVR = 0x9631;
const GLenum FRAMEBUFFER_INCOMPLETE_VIEW_TARGETS_OVR = 0x9633;
void framebufferTextureMultiviewWEBGL(GLenum target, GLenum attachment, WebGLTexture? texture, GLint level, GLint baseViewIndex, GLsizei numViews);
};
</idl>
<newfun>
<function name="framebufferTextureMultiviewWEBGL" type="void">
<param name="target" type="GLenum"/>
<param name="attachment" type="GLenum"/>
<param name="texture" type="GLuint"/>
<param name="level" type="GLint"/>
<param name="baseViewIndex" type="GLint"/>
<param name="numViews" type="GLsizei"/>
</function>
</newfun>
<newtok>
<function name="getParameter" type="any">
<param name="pname" type="GLenum"/>
Calling with the <code>pname</code> set to <code>MAX_VIEWS_OVR</code> returns the maximum number of views. The implementation must support at least 2 views.
<br/>
The return type depends on the parameter queried:
<table width="30%">
<tr><th>pname</th><th>returned type</th></tr>
<tr><td>MAX_VIEWS_OVR</td><td>GLint</td></tr>
</table>
</function>
</newtok>
<newtok>
<function name="getFramebufferAttachmentParameter" type="any">
<param name="target" type="GLenum"/>
<param name="attachment" type="GLenum"/>
<param name="pname" type="GLenum"/>
Calling with the <code>pname</code> parameter set to <code>FRAMEBUFFER_ATTACHMENT_TEXTURE_NUM_VIEWS_OVR</code> returns the number of views of the framebuffer object attachment.
Calling with the <code>pname</code> parameter set to <code>FRAMEBUFFER_ATTACHMENT_TEXTURE_BASE_VIEW_INDEX_OVR</code> returns the base view index of the framebuffer object attachment.
<br/>
The return type depends on the parameter queried:
<table width="30%">
<tr><th>pname</th><th>returned type</th></tr>
<tr><td>FRAMEBUFFER_ATTACHMENT_TEXTURE_NUM_VIEWS_OVR</td><td>GLsizei</td></tr>
<tr><td>FRAMEBUFFER_ATTACHMENT_TEXTURE_BASE_VIEW_INDEX_OVR</td><td>GLint</td></tr>
</table>
</function>
</newtok>
<errors>
<error>
The error <code>INVALID_OPERATION</code> is generated by calling <code>framebufferTextureMultiviewWEBGL</code> with a <code>texture</code> parameter that does not identify a 2D array texture.
</error>
<error>
The error <code>INVALID_OPERATION</code> is generated by calling <code>framebufferRenderbuffer</code>, <code>framebufferTexture2D</code>, <code>framebufferTextureLayer</code>, or <code>framebufferTextureMultiviewWEBGL</code> with a <code>target</code> parameter that identifies an opaque multiview framebuffer.
</error>
<error>
The error <code>INVALID_OPERATION</code> is generated by calling <code>deleteFramebuffer</code> with a <code>buffer</code> parameter that identifies an opaque multiview framebuffer.
</error>
<error>
The error <code>INVALID_ENUM</code> is generated by calling <code>getFramebufferAttachmentParameter</code> with an <code>attachment</code> parameter other than <code>BACK</code>, <code>DEPTH</code> or <code>STENCIL</code> when the <code>target</code> parameter identifies an opaque multiview framebuffer.
</error>
<error>
The error <code>INVALID_ENUM</code> is generated by calling <code>getFramebufferAttachmentParameter</code> with the <code>pname</code> parameter set to <code>FRAMEBUFFER_ATTACHMENT_OBJECT_NAME</code> when the <code>target</code> parameter identifies an opaque multiview framebuffer.
</error>
<error>
The error <code>INVALID_VALUE</code> is generated by calling <code>framebufferTextureMultiviewWEBGL</code> with a non-null <code>texture</code> in the following cases:
<ul>
<li>if <code>numViews</code> is less than one</li>
<li>if <code>numViews</code> is more than <code>MAX_VIEWS_OVR</code></li>
<li>with the parameters set so that <code>baseViewIndex</code> + <code>numViews</code> is larger than the value of <code>MAX_ARRAY_TEXTURE_LAYERS</code></li>
<li>if <code>baseViewIndex</code> is negative</li>
</ul>
</error>
<error>
The error <code>INVALID_FRAMEBUFFER_OPERATION</code> is generated by commands that read from the framebuffer such as <code>BlitFramebuffer</code>, <code>ReadPixels</code>, <code>CopyTexImage*</code>, and <code>CopyTexSubImage*</code>, if the number of views in the current read framebuffer is greater than one.
</error>
<error>
The error <code>INVALID_OPERATION</code> is generated by attempting to draw if the active program declares a number of views and the number of views in the draw framebuffer does not match the number of views declared in the active program.
</error>
<error>
The error <code>INVALID_OPERATION</code> is generated by attempting to draw if the number of views in the current draw framebuffer is greater than one and the active program does not declare a number of views.
</error>
<error>
The error <code>INVALID_OPERATION</code> is generated by attempting to draw if the number of views in the current draw framebuffer is greater than one and transform feedback is active.
</error>
<error>
The error <code>INVALID_OPERATION</code> is generated by attempting to draw or calling <code>clear</code> if the number of views in the current draw framebuffer is greater than one and a timer query is active.
</error>
</errors>
<samplecode xml:space="preserve">
<pre>
var gl = document.createElement('canvas').getContext('webgl2');
var ext = gl.getExtension('WEBGL_multiview');
var fb = gl.createFramebuffer();
gl.bindFramebuffer(gl.DRAW_FRAMEBUFFER, fb);
var colorTex = gl.createTexture();
gl.bindTexture(gl.TEXTURE_2D_ARRAY, colorTex);
gl.texStorage3D(gl.TEXTURE_2D_ARRAY, 1, gl.RGBA8, 512, 512, 2);
ext.framebufferTextureMultiviewWEBGL(gl.DRAW_FRAMEBUFFER, gl.COLOR_ATTACHMENT0, colorTex, 0, 0, 2);
var depthStencilTex = gl.createTexture();
gl.bindTexture(gl.TEXTURE_2D_ARRAY, depthStencilTex);
gl.texStorage3D(gl.TEXTURE_2D_ARRAY, 1, gl.DEPTH32F_STENCIL8, 512, 512, 2);
ext.framebufferTextureMultiviewWEBGL(gl.DRAW_FRAMEBUFFER, gl.DEPTH_STENCIL_ATTACHMENT, depthStencilTex, 0, 0, 2);
gl.drawElements(...); // draw will be broadcasted to the layers of colorTex and depthStencilTex.
</pre>
</samplecode>
<samplecode xml:space="preserve">
<pre>
var gl = document.createElement('canvas').getContext('webgl');
var ext = gl.getExtension('WEBGL_multiview');
// ... obtain opaque multiview framebuffer "fb" from another web API here ...
gl.bindFramebuffer(gl.FRAMEBUFFER, fb);
gl.drawElements(...); // draw will be broadcasted to the views of the opaque multiview framebuffer.
// You can not call framebufferTextureMultiviewWEBGL to change the attachments of "fb", only draw to it.
</pre>
</samplecode>
<samplecode xml:space="preserve">
<pre>
#version 300 es
#extension GL_OVR_multiview : require
precision mediump float;
layout (num_views = 2) in;
in vec4 inPos;
uniform mat4 u_viewMatrix0;
uniform mat4 u_viewMatrix1;
void main() {
if (gl_ViewID_OVR == 0u) {
gl_Position = u_viewMatrix0 * inPos;
} else {
gl_Position = u_viewMatrix1 * inPos;
}
}
</pre>
</samplecode>
<history>
<revision date="2016/11/11">
<change>Initial revision.</change>
</revision>
<revision date="2016/11/25">
<change>Specified what happens when the number of views doesn't match or if the number of views is one.</change>
</revision>
ยด
<revision date="2016/12/21">
<change>Specified what happens on invalid num_views declarations and if assignment to gl_Position.x is inside a larger expression.</change>
</revision>
<revision date="2017/01/12">
<change>Filled in getFramebufferAttachmentParameter and extension macro specs, formatted the documentation better, and added a simple API usage example.</change>
</revision>
<revision date="2017/03/10">
<change>Removed the core spec changes and made the specification follow the OVR_multiview specification more closely.</change>
</revision>
<revision date="2017/05/19">
<change>Introduced the concept of an opaque multiview framebuffer and fixed example code.</change>
</revision>
<revision date="2017/05/23">
<change>Made the extension compatible with WebGL 1.0 and fixed example shader code.</change>
</revision>
<revision date="2017/07/21">
<change>Specified some errors to be generated at draw time and made the extension compatible with emscripten.</change>
</revision>
<revision date="2017/08/08">
<change>Rolled back shader restrictions.</change>
</revision>
<revision date="2017/08/17">
<change>Required a multiview program to draw to a multiview framebuffer.</change>
</revision>
<revision date="2017/10/26">
<change>Took changes in the native OVR_multiview specification into account, added a more elaborate example including a depth/stencil texture, and an explicit mention that texture arrays are only supported in WebGL 2.0.</change>
</revision>
<revision date="2018/01/03">
<change>Moved to draft status.</change>
</revision>
<revision date="2018/07/26">
<change>Fixed off-by-one issue in validating baseViewIndex + numViews.</change>
</revision>
</history>
</draft>
|
