The complete list of promoted extensions in WebGL2

问题

I got a chance to update our renderer we use to WebGL2. To make the renderer as backward compatible as possible we keep tracking of loaded extensions( as we did before the upgrade ) and emulate extensions even if such extension was promoted. The renderer does a few relevant things with extensions. From outside, everything is quite transparent.

To make it work smoothly, I need the complete list of promoted extensions. Have found few blogs, but those lists are not complete. Other lists which I have found on GitHub look wrong because they have redundant extensions which were in fact not promoted or were dropped. I have not found much in the docs.

So, I did some empirical research and found :

// 12 extensions were promoted in WebGL2 without surprises
[
  'ANGLE_instanced_arrays',
  'EXT_blend_minmax',
  'EXT_frag_depth',
  'EXT_shader_texture_lod',
  'EXT_sRGB',
  'OES_element_index_uint',
  'OES_standard_derivatives',
  'OES_texture_float',
  'OES_texture_half_float',
  'OES_vertex_array_object',
  'WEBGL_depth_texture',
  'WEBGL_draw_buffers',
]

Particularly I'm concerned about OES_texture_float_linear and OES_texture_half_float_linear extensions which are not in my list. Implementation of WebGL2 I have locally has OES_texture_float_linear but does not have OES_texture_half_float_linear, while WebGL had both of them. I'm aware that in the WebGL1 context OES_texture_float_linear acts a bit differently, so my intuition says there could be problems.

Also, something weird happened with the disjoint_timer_query extension. That extension was merged in partially. WebGL2 contexts got some properties of that extension. I have disjoint_timer_query_webgl2 in Chrome which has all the properties except one getQueryObject which was renamed to getQueryParameter, but in Firefox the disjoint_timer_query extension is still available with a WebGL2 context.

So, is that list complete? And, particularly, should OES_texture_half_float_linear be on the list? And why is it gone, while the analogous OES_texture_float_linear stayed?

Appreciate your help.

-

So final answer ( probably ) should be :

// 14 extensions were promoted in WebGL2
[
  'ANGLE_instanced_arrays',
  'EXT_blend_minmax',
  'EXT_frag_depth',
  'EXT_shader_texture_lod',
  'OES_element_index_uint',
  'OES_standard_derivatives',
  'OES_texture_float',
  'OES_texture_half_float',
  'OES_vertex_array_object',
  'WEBGL_depth_texture',
  'WEBGL_draw_buffers',
  /* with caveats */
  'EXT_sRGB',
  'OES_texture_half_float_linear',
  'EXT_disjoint_timer_query',
]

Please note that last three extensions were promoted with caveats. Extension EXT_sRGB lost a constant SRGB_ALPHA. Extension OES_texture_half_float_linear was promoted while analogous OES_texture_float_linear was not. Extension EXT_disjoint_timer_query promoted partially. Some properties of that extension appeared in WebGL2 context, while other properties were moved to EXT_disjoint_timer_query_webgl2 extension. Also, currently ( 2017.05.16 ) Firefox WebGL2 context still has EXT_disjoint_timer_query extensions and no EXT_disjoint_timer_query_webgl2 extension.

回答1:

WebGL2 requires support for half and floating point textures. It also requires filtering for half textures but it does not require support for filtered floating point textures.

That's why OES_texture_half_float_linear missing and OES_texture_float_linear is optional. Most mobile devices do not support filtering for floating point textures.

In other words you should add OES_texture_half_float_linear to your list of promoted extensions.

Another extension that has a strange history is EXT_color_buffer_float. WebGL1 shipped without it. It was assumed to render to a floating point texture all you needed was first OES_texture_float and then make a floating point texture, attach it to a framebuffer and check gl.checkFramebufferStatus. But, a year or so after WebGL shipped someone pointed out that was not enough and so EXT_color_buffer_float was added but it was not enforced because doing so would have broke pages.

In WebGL2 it is enforced. You can not render to a floating point texture without enabling EXT_color_buffer_float. Same for EXT_color_buffer_half_float.

来源：https://stackoverflow.com/questions/43987719/the-complete-list-of-promoted-extensions-in-webgl2