移植到Qt5后，OpenGL应用程序看起来很奇怪

Question

I recently ported my engine from QGLWidget to QWindow . Everything works nice, except texturing. They appear with a lot of holes, dark and really weird.

Example to show what I mean: (Broken build (QWindow))

Second example: (Working build QGLWidget):

To set up the texture I used QOpenGLTexture . It shows warning that glTextureView can't be resolved, but still works. In QGLWidget version I used QGLWidget::convertToGLFormat , and some raw OpenGL calls.

Code for QGLWidget version:

if(!mProgram.isLinked())
{
    qCritical() << tr("Error: the shader program is not linked, object name: %1").arg(mName);
    return false;
}

if(mTextureID != 0)
{
    qCritical() << tr("Error: texture already set, object name: %1").arg(mName);
    return false;
}

QImage tex;
bool loadok = tex.load(path);
if(!loadok)
{
    qCritical() << tr("Error: failed to load the image, object name: %1").arg(mName);
    return false;
}

tex = QGLWidget::convertToGLFormat(tex);



glGenTextures(1, &mTextureID);
if(mTextureID == 0)
{
    qCritical() << tr("Error: failed to generate the texture, object name: %1").arg(mName);
    return false;
}
mVAO.bind();

glActiveTexture(GL_TEXTURE0);
glBindTexture(GL_TEXTURE_2D, mTextureID);

glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA, tex.width(), tex.height(), 0, GL_RGBA, GL_UNSIGNED_BYTE, tex.constBits());
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);

mProgram.setUniformValue("objectTexture", 0);

mVAO.release();

return true;

Code for QWindow version:

if(!mProgram.isLinked())
{
    qCritical() << tr("Error: the shader program is not linked, object name: %1").arg(mName);
    return false;
}

QImage img;
bool ok = img.load(path);
if(!ok)
{
    qCritical() << tr("Error: failed to load the image, object name: %1").arg(mName);
    return ok;
}

ok = mTexture.create();

qDebug() << img.size();

if(!ok)
{
    qCritical() << tr("Error: create the texture, object name: %1").arg(mName);
    return ok;
}


mTexture.setFormat(QOpenGLTexture::RGBA8_UNorm);
mTexture.setData(img);

QOpenGLVertexArrayObject::Binder vaoBinder(&mVAO);
glActiveTexture(GL_TEXTURE0);
mTexture.bind();

mProgram.setUniformValue("objectTexture", 0);


return ok;

Any ideas what could have caused this?

Answer 1

I figured this out!!! Using QGLWidget::convertToGLFormat flipped the texure over Y axis for me. QOpenGLTexture doesn't do that. So a simple line in the shader fixed this.

varying highp vec2 outUV;
uniform sampler2D objectTexture;
void main()
{
    vec2 flipped_texcoord = vec2(outUV.x, 1.0 - outUV.y);
    gl_FragColor = texture2D(objectTexture, flipped_texcoord);
}

Or I can just use img = img.mirrored(); to do that in C++.