Bug 212240 – PVRTC compressed textures are failing with ANGLE backend

• Status: RESOLVED
• Resolution: FIXED
• Component: WebGL

[Dean Jackson]

extensions/webgl-compressed-texture-pvrtc.html is failing.

uploading data with COMPRESSED_RGB_PVRTC_2BPPV1_IMG produces an INVALID_VALUE

[Radar WebKit Bug Importer]

<rdar://problem/63517385>

[Kenneth Russell]

Inside ANGLE, ValidateCompressedTexImage2D in src/libANGLE/validationES2.cpp, this is the code which is failing:

   GLuint blockSize = 0;
    if (!formatInfo.computeCompressedImageSize(Extents(width, height, 1), &blockSize))
    {
        context->validationError(GL_INVALID_OPERATION, kIntegerOverflow);
        return false;
    }

    if (imageSize < 0 || static_cast<GLuint>(imageSize) != blockSize)
    {
        context->validationError(GL_INVALID_VALUE, kCompressedTextureDimensionsMustMatchData);   // <--- fails
        return false;
    }

Here, imageSize is 32 but blockSize is 0. computeCompressedImageSize failed to compute the compressed image size.

[Dean Jackson]

It comes from formatutils.cpp

AddCompressedFormat(&map, GL_COMPRESSED_RGB_PVRTC_2BPPV1_IMG....

produces a pixelBytes value of 0, because compressedBlockSize is 1, and it is divided by 8 to produce 0.

[Dean Jackson]

If I update the values in formatutils.cpp to use 32 and 16 for blocksize on 4bpp and 2bpp respectively, things start working much better.

The rendering looks good too.

I still get some errors though:

testing COMPRESSED_RGBA_PVRTC_2BPPV1_IMG 4x4
PASS getError was expected value: NO_ERROR : uploading compressed texture
PASS getError was expected value: INVALID_OPERATION : trying to generate mipmaps from compressed texture

expected

actual

PASS texture rendered correctly
PASS getError was expected value: INVALID_VALUE : non 0 border
FAIL getError expected: INVALID_OPERATION. Was INVALID_VALUE : invalid dimensions
FAIL getError expected: INVALID_OPERATION. Was INVALID_VALUE : invalid dimensions
FAIL getError expected: INVALID_OPERATION. Was INVALID_VALUE : invalid dimensions
FAIL getError expected: INVALID_OPERATION. Was INVALID_VALUE : invalid dimensions
PASS getError was expected value: NO_ERROR : compressedTexSubImage2D allowed for reloading of complete textures
PASS getError was expected value: INVALID_OPERATION : compressedTexSubImage2D not allowed for partial texture updates
PASS getError was expected value: INVALID_OPERATION : compressedTexSubImage2D not allowed for partial texture updates
PASS getError was expected value: INVALID_OPERATION : compressedTexSubImage2D not allowed for partial texture updates
PASS getError was expected value: INVALID_OPERATION : compressedTexSubImage2D not allowed for partial texture updates

[Kenneth Russell]

Created attachment 400013 [details]
Patch for testing

Patch for testing

[Kenneth Russell]

Dean, could you try this patch instead? From reading the PVRTC extension spec:

https://www.khronos.org/registry/OpenGL/extensions/IMG/IMG_texture_compression_pvrtc.txt

I think the compressed block size for 2BPP textures is 16x8, and for 4BPP textures, 8x8.

This equates to a block size of 256 bits for both formats.

[Dean Jackson]

Created attachment 400016 [details]
Patch

[EWS Watchlist]

Note that there are important steps to take when updating ANGLE. See http://trac.webkit.org/wiki/UpdatingANGLE

[Kenneth Russell]

Comment on attachment 400016 [details]
Patch

LGTM

[Kenneth Russell]

Looks good to me but I think the CQ's going to reject my review bit!

[Dean Jackson]

I will land manually to avoid any robots checking your status!

[Dean Jackson]

Committed r262044: <https://trac.webkit.org/changeset/262044>