I have a CSGL shader that declares this uniform...
uniform float Targets[6];
I'm writing a gnome extension that attempts to set this with the following code in extension.js...
let fx = new Clutter.ShaderEffect(
{ shader_type: Clutter.ShaderType.FRAGMENT_SHADER }
);
var targets = [0.0, 0.1, 0.2, 0.3, 0.4, 0.5];
fx.set_uniform_value('Targets', targets);
fx.set_shader_source(shader);
However, the call to set_uniform_value() is failing. Is there a way to pass an array value to a CSGL shader from extension.js ?
Related
Using Qt Quick 3D QML and without having additional C++, how could I multiply two quaternions?
I have a fixed rotation value given in quaternion (Qt.quaternion(a,b,c)), to which I would like to add a variable part.
Documentation is very scarce about that (I only found quaternion and Transform) and apparently there is no "times()" property similar to the one from vector. On the C++ side, I can multiply and normalize quaternions (QQuaternion)
I would recommend writing your own JavaScript function doing the multiplication. One example implementation (multiplyQuaternion()) can be seen in this answer to another question.
You can also take a look into implementation of inline const QQuaternion operator*(const QQuaternion &q1, const QQuaternion& q2) in QQuaternion class for reference when writing your own JS function.
Another possibility might be to utilize some ready-made JS implementation (if found) by importing a JS file in question into your QML.
You could also write QObject-based C++ wrapper which utilizes QQuaternion class and then expose it to QML. But you would have to link with Qt Gui module and write quite a lot of boilerplate code because of that one function which probably doesn't make too much sense.
In Qt6, there are many useful methods on quaternion for multiplying with another quaternion, vector, or scalar values.
var a = Qt.quaternion(1 / Math.sqrt(2), 1 / Math.sqrt(2), 0, 0);
var b = Qt.quaternion(1 / Math.sqrt(2), 0, 1 / Math.sqrt(2), 0);
var c = b.times(a);
console.log(c.toString()); // QQuaternion(0.5, 0.5, 0.5, -0.5)
var a = Qt.quaternion(0.5,0.5,0.5,-0.5);
var b = Qt.vector3d(4,5,6);
var c = a.times(b);
console.log(c.toString()); // QVector3D(5, -6, -4)
var a = Qt.quaternion(1,2,3,4);
var b = 4.48;
var c = a.times(b);
console.log(c.toString()); // QQuaternion(4.48, 8.96, 13.44, 17.92)
See https://doc.qt.io/qt-6/qml-quaternion.html
I am using QT QOpenGLWidget, I want to unproject my mouse click position back into 3D, so I used glReadPixels. (I also read about the source code of Pangolin, a very good rotation, translation, zoom example, it uses glReadPixels as well)
Here's part of my simple code:
void myGLWidget::initializeGL()
{
glClearColor(0.2, 0.2, 0.2, 1.0); //background color
glClearDepthf(1.0); //set depth test
glEnable(GL_DEPTH_TEST); //enable depth test
}
void myGLWidget::paintGL()
{
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT); //clear color and depth buffer
glMatrixMode(GL_MODELVIEW);
glLoadMatrixf(cameraView_.data()); // cameraView_ is a QMatrix4x4
drawingTeapot();
// reading pixels in paintGL works well!!! returns lots of 1s
GLfloat zs[10 * 10];
glReadPixels(0, 0, 10, 10, GL_DEPTH_COMPONENT, GL_FLOAT, &zs);
}
void myGLWidget::mousePressEvent(QMouseEvent *event)
{
// glReadBuffer(GL_FRONT); // also tried this, nothing works
GLfloat zs[10 * 10];
glReadPixels(0, 0, 10, 10, GL_DEPTH_COMPONENT, GL_FLOAT, &zs);
GLenum e = glGetError(); // this gives 1282 err code!!!
}
I'm using macOS Sierra, Pangolin works perfectly on my laptop, however, my qt project does work??!!
By saying not working, I mean the output variable zs remains random values like 0 and 123123e-315 and it never change before and after glReadPixels.
Why glReadPixels works only in PaintGL function??
I also tried python version, it gives my an error says:
File "errorchecker.pyx", line 53, in OpenGL_accelerate.errorchecker._ErrorChecker.glCheckError (src/errorchecker.c:1218)
OpenGL.error.GLError: GLError(
err = 1282,
description = b'invalid operation',
baseOperation = glReadPixels,
which might be the case that:
GL_INVALID_OPERATION is generated if format is GL_DEPTH_COMPONENT and there is no depth buffer. reference from document
But I still don't know what to do
OpenGL operations should be performed only when an OpenGL context is active. This is true in the paintGL() method because this is probably set by the framework for you. You can't assume the OpenGL is active in other methods, like in other event responding methods and callbacks as mousePressEvent(), because those methods can also be run by a different thread where the OpenGL context is not active.
Related to my other question, I'm trying to render a segmentation mask to enable object picking. But I am not able to achieve the desired result.
Option 1 did not work at all. I was not able to retrieve the content of color attachment 1, or check if it existed at all (I created the attachment using only native OpenGL calls).
Using this post, I was able to reproduce the green.png and red.png images by creating a custom frame buffer with a second color attachment which is then bound and drawn to (all in paintGL()).
Somehow I had to use the person's frame buffer creation code because when I created the frame buffer myself there was always a warning saying toImage called for missing color attachment, although I attached the color attachment and textures() called on the frame buffer returned two objects. I then tried to insert my rendering code after
GLfloat red[4] = { 1.0f, 0.0f, 0.0f, 1.0f };
f->glClearBufferfv(GL_COLOR, 0, red);
GLfloat green[4] = { 0.0f, 1.0f, 0.0f, 1.0f };
f->glClearBufferfv(GL_COLOR, 1, green);
but this still resulted in the red and green image. But the code renders fine when using the normal default framebuffer. I adapted the shader to (short version for testing purposes):
void main() {
gl_FragData[0] = vec4(1.0, 1.0, 1.0, 1.0);
gl_FragData[1] = vec4(0.0, 0.0, 0.0, 1.0);
}
Since I was able to produce the red and green image, I'm assuming there must be a way to retrieve the frag data with this custom framebuffer. The solution I have right now is a complete (!) copy of the program and another dedicated fragment shader which's sole purpose is to render the segmentation, and perform all OpenGL draw calls a second time. As you can guess, this is a somewhat ugly solution, although the scenery is not that large and my computer is able to handle it easily. Has anyone got an idea/link?
If you want to write to multiple render targets in a Fragment shader, then you have to declare multiple output variables:
#version 330
layout(location = 0) out vec4 fragData0;
layout(location = 1) out vec4 fragData1;
void main()
{
fragData0 = vec4(1.0, 1.0, 1.0, 1.0);
fragData1 = vec4(0.0, 0.0, 0.0, 1.0);
}
From GLSL version 1.1 (#version 110, OpenGL 2.0) to GLSL version 1.5 (#version 150, OpenGL 3.2), the same can be achieved by writing to the built in fragment shader output variable gl_FragData.
void main()
{
gl_FragData[0] = vec4(1.0, 1.0, 1.0, 1.0);
gl_FragData[1] = vec4(0.0, 0.0, 0.0, 1.0);
}
See also Fragment Shader Outputs - Through The Ages
To use multiple render targets in Qt, a 2nd color attachment has to be add to the framebuffer and the list of color buffers has to be specified by glDrawBuffers:
QOpenGLShaderProgram *program;
QOpenGLFramebufferObject *fb;
int fb_width;
int fb_height,
fb = new QOpenGLFramebufferObject( fb_width, fb_height );
fb->addColorAttachment( fb_width, fb_height );
glViewport(0, 0, fb_width, fb_height);
fb->bind();
glClearColor(0, 0, 0, 1);
glClear( GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT );
GLenum buffers[] = { GL_COLOR_ATTACHMENT0, GL_COLOR_ATTACHMENT1 };
glDrawBuffers(2, buffers);
program->bind();
// ..... do the drawing
program->release();
fb->release();
The OpenGL texture objects which are attached to the framebuffer, can be accessed:
QVector<GLuint> fb_textrues = fb->textures();
I'm doing an opengl project in Qt with the new QOpenGLWidget class.
I'm just trying to get the opengl world coordinates of my mouse when I click.
I've found a lot of ways to do it but some were obsolete and the others don't work. Then I found the QVector3D::unproject() function but I don't get the right coordinates.
This is a part of my code so far :
QMatrix4x4 modelView;
modelView.setToIdentity();
modelView.lookAt(m_camera.getPosition(), m_camera.getTarget(), m_camera.getUp());
QMatrix4x4 projection;
projection.perspective(70.0, width() / height(), 0.1, 120.0);
GLint view[4];
glGetIntegerv(GL_VIEWPORT, &view[0]);
QVector3D worldPosition = QVector3D(event->pos().x(), event->pos().y(), 0).unproject(modelView, projection, QRect(view[0], view[1], view[2], view[3]));
qDebug() << worldPosition;
Do you know why I get (1.96532, -3.93444, 4.93216) where I should have (-0.5, -0.5, 0.0) ?
I have an old code that uses,
Rect r;
GetPortBounds(some_bitmap,&r);
PixMapHandle somehandle = GetGWorldPixMap(some_bitmap);
if(LockPixels(somehandle)){
TPixel *data = (TPixel *) GetPixBaseAddr(somehandle);
long row_bytes = GetPixRowBytes(somehandle);
// doing something
UnlockPixels(somehandle);
}
Can anyone help me with the replacement code in quartz 2d
To modify a bitmap with Quartz you can initialize a CGContextRef with the image and draw to that context with CGContextDraw... routines.
(I wrote the following sample code for a NSView subclass. It's a bit inefficient. If you use the code, separate the stuff you can keep around in iVars.)
- (void)drawRect:(NSRect)dirtyRect
{
//Load an image ...
NSImage* image = [[NSImage alloc] initWithContentsOfFile:#"/Library/Desktop Pictures/Grass Blades.jpg"];
CGImageRef testImage = [[[image representations] objectAtIndex:0] CGImage];
[image release];
CGDataProviderRef dataProvider = CGImageGetDataProvider(testImage);
//... and retrieve its pixel data
CFDataRef imageData = CGDataProviderCopyData(dataProvider);
void* pixels = (void*)CFDataGetBytePtr(imageData);
CGColorSpaceRef colorspace = CGColorSpaceCreateWithName(kCGColorSpaceGenericRGB);
//Init a quartz context that uses the pixel data memory as buffer
CGContextRef drawContext = CGBitmapContextCreate(pixels, CGImageGetWidth(testImage), CGImageGetHeight(testImage), CGImageGetBitsPerComponent(testImage), CGImageGetBytesPerRow(testImage), colorspace, CGImageGetBitmapInfo(testImage));
CGContextSetRGBFillColor(drawContext, 0.8, 0.8, 0.8, 1.0);
//Do something with the newly created context
CGContextFillRect(drawContext, CGRectMake(20.0, 20.0, 200.0, 200.0));
CGColorSpaceRelease(colorspace);
CGImageRef finalImage = CGBitmapContextCreateImage(drawContext);
//Draw the modified image to the screen
CGContextDrawImage([[NSGraphicsContext currentContext] graphicsPort], dirtyRect, finalImage);
CFRelease(imageData);
CGImageRelease(finalImage);
CGContextRelease(drawContext);
}