I agree. I had not looked at the spec. before proposing that language. :-[On 2012/12/07 13:33, Kenneth Russell wrote:
On Thu, Dec 6, 2012 at 7:32 PM, Mark Callow <firstname.lastname@example.org> wrote:On 2012/12/07 12:07, Jeff Gilbert wrote: At the absolute minimum, we need wording in the spec that spells this out: "We send decoded image data top-row-first into texImage2D, which, per spec, expects bottom-row-first data. This means that textures uploaded this way will be upside down compared to textures uploaded via other methods. You can force HTML element uploads to upload bottom-row-first by using UNPACK_FLIP_Y_WEBGL=true, but this also flips the order that TypedArray rows are uploaded." I have no objection to adding a note to the spec. I would prefer something along the lines of: The default texture coordinate system in OpenGL is such that the first row of data loaded by texImage2D will appear at bottom of the texture. However the first row of data in HTML elements is the logical top of the image therefore textures uploaded from HTML elements will appear upside down. One way of adjusting for this is to set UNPACK_FLIP_Y_WEBGL=true. Then texImage2D will flip the rows of data as it uploads them. UNPACK_FLIP_Y_WEBGL affects the operation of texImage2D for all data sources.This seems like too much text to me. http://www.khronos.org/registry/webgl/specs/latest/#PIXEL_STORAGE_PARAMETERS already defines UNPACK_FLIP_Y_WEBGL very clearly. The only text that should possibly be added in my opinion is a brief note in http://www.khronos.org/registry/webgl/specs/latest/#5.14.8 under the texImage2D and texSubImage2D overloads taking HTML elements and ImageData, which already reference the above section. I'm still unconvinced that changes are needed here so if someone could please propose spec text in this context it would be helpful.
How about adding the following in 5.14.8 after "Uploads the given element or image data to the currently bound WebGLTexture":
Note: HTML elements have an upper left origin. To match the texture image orientation to the element's display in HTML, either set UNPACK_FLIP_Y_WEBGL=true or change texture coordinate v.
Note: HTML elements have an upper left origin. To match the texture image orientation to the element's display in HTML call gl.pixelStorei(gl.UNPACK_FLIP_Y_WEBGL, true).
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