KTX 2.0 texture format unable to GLupload | DEBUG_OUTPUT printing error on ktx 1.0 | typo in the documentation about ktx-software HOT 5 CLOSED

There is not enough information for me to take action on the first item. I need your actual example. The one in the doc only shows the key pieces. If the texture needs transcoding you must do it before calling ktxTexture_GLUpload. If you do not, KTX_INVALID_OPERATION will be returned.

The error cannot be avoided. In OpenGL there is no query to determine if the implementation accepts the given format. Rather than some error-prone heuristics the loader simply attempts to load the texture. If GL_INVALID_ENUM is returned, the loader checks if it has a software decoder for the format (only true for ETC[12]). If it does, it clears the error, decodes the texture and uploads the decoded texture. If not, it returns the GL_INVALID_ENUM in glerror.

I've fixed the typo in the documentation. It will be in the next release.

from ktx-software.

@Raffaello

1. Automatically transcoding would require guessing the needs and intent of the application. The choice of target needs to be in the hands of the application writer.

from ktx-software.

@MarkCallow thanks.

1. Doing the transcoding is enough to be succeful in GLUpload. I am wondering wouldn't be possible to have a function to do also the transcoding if needed for an easier usage?

2. thanks, anyway that led me to improve my handling error routine.

3. 👍

from ktx-software.

@MarkCallow One more thing, I noticed that GLUpload or `ktTexture_createdFromNamedFile' doesn't flip the Y of the images. Is there anything available in the ktxlib to tell to flip Y of the images?
As it is not really convinient after the texture being created to flip it or negate the tex coords...

from ktx-software.

You can set the orientation when you create a texture with ktx create. A y-flip will be performed if the input image orientation differs from that specified. (Default origin is top-left or, in terms of increasing s & t, right-down). You should make textures with the orientation you desire. If the texture and coordinates do not match, it is fairly easy to modify them. E.g,

    if (kTexture->orientation.x == KTX_ORIENT_X_LEFT)
        sign_s = -1;
    if (kTexture->orientation.y == KTX_ORIENT_Y_UP)
        sign_t = -1;

    if (sign_s < 0 || sign_t < 0) {
        // Transform the texture coordinates to get correct image orientation.
        for (uint32_t i = 0; i < vertexBuffer.size(); i++) {
            if (sign_t < 1) {
                vertexBuffer[i].uv[1] = vertexBuffer[i].uv[1] * -1 + 1;
            }
            if (sign_s < 1) {
                vertexBuffer[i].uv[0] = vertexBuffer[i].uv[0] * -1 + 1;
            }
        }
    }

If you do not want to modify the uv coordinates before loading it is easy to apply the texture coordinate transform in the vertex shader.

As with automatic transcoding, an automatic flip would require second guessing the application and would be wrong in some cases.

Re. ktxTexture_CreateFromNamedFile we chose to keep image processing out of libktx. Applications need to perform any necessary flip before calling this function.

from ktx-software.