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Re: [Public WebGL] Moving float color buffer proposals to draft (was Re: Fixing the OES_texture_float mess)



On 2012/11/16 12:40, Gregg Tavares (社用) wrote:

I'm not following you

type + format = the format of the data I'm passing to texImage2D
internal_format = the format I want the driver to store the texture except that in ES type also influences that storage
At least we agree about something.

This is an unrenderable texture according to ES

  glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA, 2, 2, 0, GL_RGBA, GL_UNSIGNED_BYTE, dataFor4RGBA8Pixels);
  glTeximage2D(GL_TEXTURE_2D, 0, GL_RGBA, 1, 1, 0, GL_RGBA, GL_UNSIGNED_SHORT_4_4_4_4, dataFor1RGBA4Pixel);

The types are different therefore the mips don't match therefore the texture is not "texture complete" and will not render. From the spec
No disagreement here either. My point is that type influences the storage format only because ES essentially uses the external format as the storage format.


If WebGL implementations are allowed to chose any random format to upload an image than it would be impossible to specific the second level

  gl.texImage2D(GL_TEXTURE_2D, 0, GL_RGBA, image)   // implementation chooses the type.
  gl.texImage2D(GL_TEXTURE_2D, 1, GL_RGBA, 1, 1, 0, GL_RGBA, unknown_type!!!!!, dataForPixels);

This would also fail

  gl.texImage2D(GL_TEXTURE_2D, 0, GL_RGBA, image)   // implementation chooses the type.
  gl.texSubImage2D(GL_TEXTURE_2D, 0, 0, 0, 1, 1, GL_RGBA, unknown_type!!!!, dataForPixels);

What type is the developer suppose to supply for this second call to gl.texImage2D or to gl.texSubImage2D? If the implementation chose the type the developer wouldn't know what type WebGL supplied. They could maybe guess what WebGL if they supplied the image but the image could be user supplied and the developer would have no way of knowing what WebGL created.
What I am suggesting is something like this:

gl.texImage2D(GL_TEXTURE_2D, 0, GL_RGBA8888, /* no <format>, no <type>, */ image);
gl.texImage2D(GL_TEXTURE_2D, 1, GL_RGBA8888, 1, 1, 0, GL_RGBA, GL_UNSIGNED_BYTE, dataForPixels);

gl.texImage2D(GL_TEXTURE_2D, 0, GL_RGBA8888, /* no format param, no type param, */ image);
gl.texSubImage2D(GL_TEXTURE_2D, 1, 0, 0, 1, 1, GL_RGBA, GL_UNSIGNED_BYTE, dataForPixels);

There would be a table that gives you the valid combinations of <format>, <type> and <internalformat> and another table giving the valid <internalformat> values that can be used with ImageData and HTML{Image,Canvas,Video}Element. <format> and <type> don't serve any purpose for these elements when internalformat controls the storage format.

The definition of texSubImage2D would have to be modified to say format and type must make a valid combination with the internalformat specified for the original texture.

Yes I realize this would be a big difference from ES 2.0 and therefore likely unacceptable. I'm looking ahead.

Regards

    -Mark

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