阿勇的blog

3月 11 週一 201323:07
immediate mode? display list? vertex array?

immediate mode

The easiest way to do drawing in OpenGL is using the Immediate Mode. For this, you use the glBegin() function which takes as one parameter the “mode” or type of object you want to draw.

glBegin(GL_LINE_LOOP);//start drawing a line loop
glVertex3f(-1.0f,0.0f,0.0f);//left of window
glVertex3f(0.0f,-1.0f,0.0f);//bottom of window
glVertex3f(1.0f,0.0f,0.0f);//right of window
glVertex3f(0.0f,1.0f,0.0f);//top of window
glEnd();//end drawing of line loop

display list

Display list is a group of OpenGL commands that have been stored (compiled) for later execution. Once a display list is created, all vertex and pixel data are evaluated and copied into the display list memory on the server machine. It is only one time process. After the display list has been prepared (compiled), you can reuse it repeatedly without re-evaluating and re-transmitting data over and over again to draw each frame.

// create one display list
GLuint index = glGenLists(1);
// compile the display list, store a triangle in it
glNewList(index, GL_COMPILE);
glBegin(GL_TRIANGLES);
glVertex3fv(v0);
glVertex3fv(v1);
glVertex3fv(v2);
glEnd();
glEndList();
...
// draw the display list
glCallList(index);

vertex array

This means that your vertices and vertex attributes and indices are in RAM.

glEnableClientState(GL_VERTEX_ARRAY);
glEnableClientState(GL_COLOR_ARRAY);
glColorPointer(3, GL_FLOAT, 0, Colors);
glVertexPointer(3, GL_FLOAT, 0, Vertices);
glDrawArrays(GL_TRIANGLES, 0, 3);
glDisableClientState(GL_VERTEX_ARRAY);
glDisableClientState(GL_COLOR_ARRAY);

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個人分類：opengl

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3月 10 週日 201320:55
OpenGL Blend

glBlendFunc — specify pixel arithmetic
void glBlendFunc(GLenum sfactor, GLenum dfactor);void glBlendFunci(GLuint buf, GLenum sfactor, GLenum dfactor);Parameters
bufFor glBlendFunci, specifies the index of the draw buffer for which to set the blend function.sfactor

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個人分類：opengl

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3月 10 週日 201317:51
Qt5 + OpenGL

前幾天發現在Qt5裡，所有的fixed function pipeline都不能編譯了。稍微google了一下，才發現，原來Qt5所有precompile的安裝包，都是用ANGLE layer來實作OpenGL ES2，也就是你要寫的是OpenGL ES2，而不是OpenGL。所以一些fixed function pipeline的function，例如glBegin/glEnd都不能用了。

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個人分類：Qt

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3月 08 週五 201322:22
Color Button for Qt (part 2)

void ColorButton::setColor(QColor color)
{
QPixmap pixmap(this->iconSize());
pixmap.fill(color);
this->setIcon(QIcon(pixmap));
selectedColor = color;
this->update();
}
void ColorButton::init(QColor color)
{
colorDialog.setCurrentColor(color);
QObject::connect(this, SIGNAL(clicked()),
&colorDialog, SLOT(open()));
QObject::connect(&colorDialog, SIGNAL(colorSelected(QColor)),
this, SLOT(setColor(QColor)));
setColor(color);
}
void ColorButton::paintEvent(QPaintEvent *event)
{
QPushButton::paintEvent(event);
QPainter painter(this);
painter.setCompositionMode(QPainter::CompositionMode_Screen);
painter.fillRect(0, 0, this->width(), this->height(), selectedColor);
}

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個人分類：Qt

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3月 08 週五 201314:33
Color Button for Qt

void ColorButton::setColor(QColor color)
{
QPixmap pixmap(this->iconSize());
pixmap.fill(color);
QPainter painter;
painter.begin(&pixmap);
painter.setPen(0xffffff-color.rgb());
painter.drawRect(0,0, pixmap.width()-1, pixmap.height()-1);
painter.end();
this->setIcon(QIcon(pixmap));
}
void ColorButton::init(QColor color)
{
colorDialog.setCurrentColor(color);
QObject::connect(this, SIGNAL(clicked()),
&colorDialog, SLOT(open()));
QObject::connect(&colorDialog, SIGNAL(colorSelected(QColor)),
this, SLOT(setColor(QColor)));
setColor(color);
}

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個人分類：Qt

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3月 04 週一 201313:49
在Qt中，使用系統預設的圖示

QStyle定義了一些系統視窗相關的風格，像是圖示和gui的樣式。 qApp->style()->standardIcon(QStyle::SP_MediaVolumeMuted

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個人分類：Qt

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3月 02 週六 201320:32
3D text on Qt with OpenGL (part 2)

這一篇，是把上一篇的文章改成一個class
header file

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個人分類：Qt

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3月 02 週六 201316:55
Qt 讀取非系統字型

使用QFontDatabase::addApplicationFont，可以直接讀取字型檔(ttc, ttf)。

#include <QFontDatabase>
QString loadFontFromFile(QString path)
{
static QString font;
static bool loaded = false;
if(!loaded)
{
loaded = true;
int loadedFontID = QFontDatabase::addApplicationFont(path);
QStringList loadedFontFamilies = QFontDatabase::applicationFontFamilies(loadedFontID);
if(!loadedFontFamilies.empty())
font = loadedFontFamilies.at(0);
}
return font;
}
QString fontName = loadFontFromFile(":/font/font2.TTC");
QFont font(fontName);

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個人分類：Qt

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3月 01 週五 201314:20
3D text on Qt with OpenGL

利用QPainterPath算出polygon之後，就可以畫出邊框
QPainterPath path;
path.addText(QPointF(0, 0), QFont("Arial", 100), QString::fromUtf8("你要不要喝紅茶ˊ_>ˋ？"));
GLuint id = glGenLists(1);
glNewList(id, GL_COMPILE);
foreach(QPolygonF polygon, path.toSubpathPolygons()){
glBegin(GL_LINE_LOOP);
foreach(QPointF point, polygon){
glVertex3f(point.rx(), -point.ry(), 0);
}
glEnd();
}
glEndList();

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