[Interest] How to construct a cubemap texture using QOpenGLTexture?

[Prashanth Udupa]

Hello there!

I want to construct a cubemap texture using QOpenGLTexture using 6 images
and use it to map reflections on a torus.

I am using the following code to construct the cubemap

const QImage posx =
QImage(":/images/posx.jpg").mirrored().convertToFormat(QImage::Format_RGBA8888);const
QImage posy = 
QImage(":/images/posy.jpg").mirrored().convertToFormat(QImage::Format_RGBA8888);const
QImage posz = 
QImage(":/images/posz.jpg").mirrored().convertToFormat(QImage::Format_RGBA8888);const
QImage negx = 
QImage(":/images/negx.jpg").mirrored().convertToFormat(QImage::Format_RGBA8888);const
QImage negy = 
QImage(":/images/negy.jpg").mirrored().convertToFormat(QImage::Format_RGBA8888);const
QImage negz = 
QImage(":/images/negz.jpg").mirrored().convertToFormat(QImage::Format_RGBA8888);

d->environment = new QOpenGLTexture(QOpenGLTexture::TargetCubeMap);
d->environment->create();
d->environment->setSize(posx.width(), posx.height(), posx.depth());
d->environment->setFormat(QOpenGLTexture::RGBA8_UNorm);
d->environment->allocateStorage();
d->environment->setData(0, 0, QOpenGLTexture::CubeMapPositiveX,
                        QOpenGLTexture::RGBA, QOpenGLTexture::UInt8,
                        (const void*)posx.constBits(), 0);
d->environment->setData(0, 0, QOpenGLTexture::CubeMapPositiveY,
                        QOpenGLTexture::RGBA, QOpenGLTexture::UInt8,
                        (const void*)posy.constBits(), 0);
d->environment->setData(0, 0, QOpenGLTexture::CubeMapPositiveZ,
                        QOpenGLTexture::RGBA, QOpenGLTexture::UInt8,
                        (const void*)posz.constBits(), 0);
d->environment->setData(0, 0, QOpenGLTexture::CubeMapNegativeX,
                        QOpenGLTexture::RGBA, QOpenGLTexture::UInt8,
                        (const void*)negx.constBits(), 0);
d->environment->setData(0, 0, QOpenGLTexture::CubeMapNegativeY,
                        QOpenGLTexture::RGBA, QOpenGLTexture::UInt8,
                        (const void*)negy.constBits(), 0);
d->environment->setData(0, 0, QOpenGLTexture::CubeMapNegativeZ,
                        QOpenGLTexture::RGBA, QOpenGLTexture::UInt8,
                        (const void*)negz.constBits(), 0);
d->environment->setWrapMode(QOpenGLTexture::ClampToEdge);
d->environment->setMinificationFilter(QOpenGLTexture::LinearMipMapLinear);
d->environment->setMagnificationFilter(QOpenGLTexture::LinearMipMapLinear);

I then bind the environment texture during paintGL() as follows

.....
d->environment->bind(0);
d->shader->setUniformValue("qt_Environment", 0);
const int nrIndicies = d->torusResolution * d->tubeResolution * 6;
glDrawElements(GL_TRIANGLES, nrIndicies, GL_UNSIGNED_INT, (void*)0);.....

Vertex shader snippet is as follows

....
varying vec3 v_TexCoord;....
void main(void){
    ....
    v_TexCoord = normalize(v_Normal + v_Position);
    ....}

The fragment shader snippet is as follows

.....
varying vec3 v_TexCoord;
uniform samplerCube qt_Environment;.....

vec4 evaluateColor(in vec3 normal, in vec3 texCoord){
    vec3 finalColor ....
    .....
    .....
    finalColor += textureCube(qt_Environment, texCoord).rgb;
    return vec4( finalColor, c_one );}
void main(void){
    gl_FragColor = evaluateColor(v_Normal, v_TexCoord);}

I also have another part of the code which renders the cubemap on a skybox.
While I am able to project the 6 images on the skybox and render it
properly, I am unable to render the reflection on a torus object in the
scene.

I am getting a well lit torus, with no reflection [
http://i.stack.imgur.com/qWRwN.png ].

You can download the complete code from here [ https://goo.gl/Wu8ccb ]

Can somebody help with this please?

Best Regards,

Prashanth

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