OpenGL中的压缩纹理批处理 [英] Compressed texture batching in OpenGL

问题描述

我想创建一个压缩贴图的地图集，但我似乎不能得到它的工作。这是一个代码片段：

I'm trying to create an atlas of compressed textures but I can't seem to get it working. Here is a code snippet:

void Texture::addImageToAtlas(ImageProperties* imageProperties)
{   
    generateTexture();  // delete and regenerate an empty texture
    bindTexture();      // bind it

    atlasProperties.push_back(imageProperties);

    width = height = 0;
    for (int i=0; i < atlasProperties.size(); i++)
    {
        width += atlasProperties[i]->width;
        height = atlasProperties[i]->height;
    }

    glPixelStorei(GL_UNPACK_ALIGNMENT, 1);
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_REPEAT);
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_REPEAT);
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);

    // glCompressedTexImage2D MUST be called with valid data for the 'pixels'
    // parameter. Won't work if you use zero/null.
    glCompressedTexImage2D(GL_TEXTURE_2D, 0, 
        GL_COMPRESSED_RGBA8_ETC2_EAC,
        width,
        height,
        0,
        (GLsizei)(ceilf(width/4.f) * ceilf(height/4.f) * 16.f),
        atlasProperties[0]->pixels);

    // Recreate the whole atlas by adding all the textures we have appended 
    // to our vector so far
    int x, y = 0;
    for (int i=0; i < atlasProperties.size(); i++)
    {
        glCompressedTexSubImage2D(GL_TEXTURE_2D,
            0,
            x,
            y,
            atlasProperties[i]->width,
            atlasProperties[i]->height,
            GL_RGBA,
            (GLsizei)(ceilf(atlasProperties[i]->width/4.f) * ceilf(atlasProperties[i]->height/4.f) * 16.f),
        atlasProperties[i]->pixels);

        x += atlasProperties[i]->width;
    }

    unbindTexture();  // unbind the texture
}

我只用2个小KTX纹理测试具有相同的大小，你可以从代码中看到我试图追加第二个旁边的第一个在x轴。

I'm testing this with just 2 small KTX textures that have the same size and as you can see from the code I'm trying to append the second one next to the first one on the x axis.

我的KTX解析工作正常，因为我可以渲染单个纹理，但一旦我尝试批处理（即一旦我使用glCompressedTexSubImage2d）我没有在屏幕上得到任何东西。

My KTX parsing works fine as I can render individual textures but as soon as I try to batch (that is as soon as I use glCompressedTexSubImage2d) I get nothing on the screen.

如果我用PNG替换压缩纹理，并将glCompressedTexImage2d和glCompressedTexSubImage2d与其非压缩版本交换，则所有这些都很有用...

It might be useful to know that all of this works fine if I replace compressed textures with PNGs and swap the glCompressedTexImage2d and glCompressedTexSubImage2d with their non-compressed versions...

其中一个我找不到任何信息的东西是纹理在图集的x和y位置。如何抵消？因此，如果第一个纹理的宽度为60像素，例如，我只是将第二个位置在61？

One of the things that I cannot find any information on is the x and y position of the textures in the atlas. How do I offset them? So if the first texture has a width of 60 pixels for example, do I just position the second one at 61?

我看过一些在线的代码，人们计算x和y位置如下：

I've seen some code online where people calculate the x and y position as follows:

x &= ~3;
y &= ~3;

这是我需要做什么，为什么？我尝试了它，但它似乎不工作。

Is this what I need to do and why? I've tried it but it doesn't seem to work.

此外，我尝试上面的代码在ARM i.mx6四核与Vivante GPU，我在网上看到glCompressedTexSubImage2d可能无法在这个板子上工作。

Also, I'm trying the above code on an ARM i.mx6 Quad with a Vivante GPU, and I get the suspicion from what I read online that glCompressedTexSubImage2d might not be working on this board.

任何人都可以帮助我吗？

Can anyone please help me out?

推荐答案

毕竟，这是一个错误，让你想在墙上打你的头。 GL_COMPRESSED_RGBA8_ETC2_EAC 实际上不支持在主板上。

After all, this was one of those mistakes that make you want to hit your head on a wall. GL_COMPRESSED_RGBA8_ETC2_EAC was actually not supported on the board.

我从标头复制了它，但没有查询设备支持的格式。我可以使用 DXT5 格式很好用这个代码。

I copied it from the headers but it did not query the device for supported formats. I can use a DXT5 format just fine with this code.

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