目前我正在使用glOrtho来缩放和平移我正在渲染的2D图形。
我已将视口设置为标准宽度和高度。然后我设置了glOrtho，以便我的截头体使屏幕坐标与世界坐标相匹配。
////////////////////////////////////////////////////////////////////
glViewport(0, 0, window_width,window_height);
glMatrixMode(GL_PROJECTION);
glLoadIdentity();
glOrtho(0, window_width,window_height,0 , 100, -100);
///////////////////////////////////////////////////////////////////
当我在鼠标回调中执行缩放功能时，我将frustrum边缘乘以缩放因子....
glOrtho( 0 * zoomOut,
window_width * zoomOut,
window_height * zoomOut,
0 * zoomOut,
100, -100);
我的问题是......如何使用鼠标位置作为中心进行缩放？
我试过这个...（其中mouseStoreX和mouseStoreY是第一次点击时存储的位置）
glOrtho( (0 -mouseStoreX )* zoomOut + mouseStoreX,
(window_width - mouseStoreX) * zoomOut + mouseStoreX,
(window_height - mouseStoreY) * zoomOut + mouseStoreY,
(0 - mouseStoreY) * zoomOut + mouseStoreY,
100, -100);
它似乎有效，但当我点击新的时候，frustrum跳了起来。我认为在做鼠标位置存储时我没有考虑zoomOut因素。
编辑************这是我最新的代码，我仍然在努力...
void ZoomOrtho(){ //ON MOUSE CLICK.....
if (zooming == false){
keyStore.LMx = keyStore.Mx; //store mouse pos for next comparison
keyStore.LMy = keyStore.My;
//get mouse pos
mouseStoreX = keyStore.Mx;//mouse pos at this moment
mouseStoreY = keyStore.My;
//get current projection matrices
glGetDoublev( GL_MODELVIEW_MATRIX, modelview );
glGetDoublev( GL_PROJECTION_MATRIX, projection );
glGetIntegerv( GL_VIEWPORT, viewport );
//flip Y for opengl reasons
winY = (float)viewport[3] - winY;
//get world mouse coordinate
gluUnProject( mouseStoreX, mouseStoreY , 0.0, modelview, projection, viewport, &posX_,&posY_, &posZ_);
// calc difference between mouse world pos and centre of 'camera'
dx = posX_ - FS.centerX;
dy = posY_ - FS.centerY;
}
//ON DRAG......
zooming = true;
//do mouse movement detection and increment zoomOut
//#################################################
int xDiff = keyStore.Mx - keyStore.LMx; //mouse drag difference in screen space just for incrementing zoom
int yDiff = keyStore.My - keyStore.LMy; //
if (xDiff > 0 && (zoomFactor >= 0.5 ) ) {
zoomFactor -= zoomInc;
if (zoomFactor < 0.5 ) {zoomFactor = 0.5;}
}
else if (xDiff < 0 && (zoomFactor <= 2.0 )) {
zoomFactor += zoomInc;
if (zoomFactor > 2.0){zoomFactor = 2.0;}
}
//#################################################
//fill structure with clipping plane values. zooms ortho projection and keeps mouse pos anchored.
FS.left = ((FS.centerX - dx - (window_width/2.0))*zoomFactor) +dx;
FS.right = ((FS.centerX -dx + (window_width/2.0))*zoomFactor)+dx ;
FS.bottom = ((FS.centerY -dy + (window_width/2.0))*zoomFactor)+dy;
FS.top = ((FS.centerY -dy - (window_width/2.0))*zoomFactor) +dy;
// store last mouse pos for next comparison.
keyStore.LMx = keyStore.Mx;
keyStore.LMy = keyStore.My;
}
void zoomRelease(){
cout << " releasing" << std::endl;
//set zoom to false so we know we are not draggin mouse anymore.
zooming = false;
keyStore.LMx = 0;
keyStore.LMy = 0;
// recenter by taking midpoint between new left and right clipping planes so dx has a reference point
FS.centreX = (FS.right-FS.left)/2.0;
}
void DrawGui(){
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
glMatrixMode(GL_PROJECTION);
glLoadIdentity();
glOrtho(FS.left, FS.right,FS.bottom, FS.top, 1, -1);
glMatrixMode( GL_MODELVIEW );
glLoadIdentity();
//do drawing
}
我假设你在第二次点击时将其值存储到mouseStoreXY中。如果是这样，这会导致跳跃。你正在使用旧mouseStoreXY的偏移量进行绘制，然后突然偏移到新的mouseStoreXY。
解决方案是持久存储投影矩阵输入，然后在每帧上逐步修改它们。
试一试：
// g++ main.cpp -o main -lglut -lGL && ./main
#include <GL/glut.h>
double centerX = 0, centerY = 0;
double width = 0, height = 0;
void mouse( int button, int state, int mx, int my )
{
// flip mouse y axis so up is +y
my = glutGet( GLUT_WINDOW_HEIGHT ) - my;
// convert mouse coords to (-1/2,-1/2)-(1/2, 1/2) box
double x = ( mx / (double)glutGet( GLUT_WINDOW_WIDTH ) ) - 0.5;
double y = ( my / (double)glutGet( GLUT_WINDOW_HEIGHT ) ) - 0.5;
if( GLUT_UP == state )
{
double preX = ( x * width );
double preY = ( y * height );
double zoomFactor = 1.5;
if( button == GLUT_LEFT_BUTTON )
{
// zoom in
width /= zoomFactor;
height /= zoomFactor;
}
if( button == GLUT_RIGHT_BUTTON )
{
// zoom out
width *= zoomFactor;
height *= zoomFactor;
}
double postX = ( x * width );
double postY = ( y * height );
// recenter
centerX += ( preX - postX );
centerY += ( preY - postY );
}
glutPostRedisplay();
}
void display()
{
glClear( GL_COLOR_BUFFER_BIT );
glMatrixMode( GL_PROJECTION );
glLoadIdentity();
glOrtho
(
centerX - ( width / 2.0 ),
centerX + ( width / 2.0 ),
centerY - ( height / 2.0 ),
centerY + ( height / 2.0 ),
-1,
1
);
glMatrixMode( GL_MODELVIEW );
glLoadIdentity();
glColor3ub( 255, 0, 0 );
glBegin( GL_TRIANGLES );
glVertex2i( 0, 0 );
glVertex2i( 150, 0 );
glVertex2i( 0, 150 );
glVertex2i( 0, 0 );
glVertex2i( -150, 0 );
glVertex2i( 0, -150 );
glEnd();
glutSwapBuffers();
}
int main( int argc, char **argv )
{
glutInit( &argc, argv );
glutInitDisplayMode( GLUT_RGBA | GLUT_DOUBLE );
glutInitWindowSize( 600, 600 );
glutCreateWindow( "GLUT" );
glutDisplayFunc( display );
glutMouseFunc( mouse );
width = glutGet( GLUT_WINDOW_WIDTH );
height = glutGet( GLUT_WINDOW_HEIGHT );
glutMainLoop();
return 0;
}
试一试：
// g++ main.cpp -o main -lglut -lGL && ./main
#include <GL/glut.h>
#include <cmath>
void getMouseCoords( int mx, int my, double& x, double& y )
{
// flip mouse y axis so up is +y
my = glutGet( GLUT_WINDOW_HEIGHT ) - my;
// convert mouse coords to (-1/2,-1/2)-(1/2, 1/2) box
x = ( mx / (double)glutGet( GLUT_WINDOW_WIDTH ) ) - 0.5;
y = ( my / (double)glutGet( GLUT_WINDOW_HEIGHT ) ) - 0.5;
}
int btn;
double baseX, baseY;
double baseWidth, baseHeight;
double centerX = 0, centerY = 0;
double width = 0, height = 0;
void mouse( int button, int state, int mx, int my )
{
baseWidth = width;
baseHeight = height;
btn = button;
getMouseCoords( mx, my, baseX, baseY );
}
void motion( int mx, int my )
{
if( btn != GLUT_LEFT_BUTTON )
{
return;
}
double x, y;
getMouseCoords( mx, my, x, y );
double preX = ( baseX * width );
double preY = ( baseY * height );
double zoomFactor = exp( baseY - y );
width = baseWidth * zoomFactor;
height = baseHeight * zoomFactor;
double postX = ( baseX * width );
double postY = ( baseY * height );
// recenter
centerX += ( preX - postX );
centerY += ( preY - postY );
glutPostRedisplay();
}
void display()
{
glClear( GL_COLOR_BUFFER_BIT );
glMatrixMode( GL_PROJECTION );
glLoadIdentity();
glOrtho
(
centerX - ( width / 2.0 ),
centerX + ( width / 2.0 ),
centerY - ( height / 2.0 ),
centerY + ( height / 2.0 ),
-1,
1
);
glMatrixMode( GL_MODELVIEW );
glLoadIdentity();
glColor3ub( 255, 0, 0 );
glBegin( GL_TRIANGLES );
glVertex2i( 0, 0 );
glVertex2i( 150, 0 );
glVertex2i( 0, 150 );
glVertex2i( 0, 0 );
glVertex2i( -150, 0 );
glVertex2i( 0, -150 );
glEnd();
glutSwapBuffers();
}
int main( int argc, char **argv )
{
glutInit( &argc, argv );
glutInitDisplayMode( GLUT_RGBA | GLUT_DOUBLE );
glutInitWindowSize( 600, 600 );
glutCreateWindow( "GLUT" );
glutDisplayFunc( display );
glutMouseFunc( mouse );
glutMotionFunc( motion );
width = glutGet( GLUT_WINDOW_WIDTH );
height = glutGet( GLUT_WINDOW_HEIGHT );
glutMainLoop();
return 0;
}
如果你想走另一条路，只需使用glTranslate和gluPerspective，就可以达到同样的效果。滚轮的鼠标事件（使用PyOpenGL）可能如下所示：
def MouseWheelScroll(self, event):
"""Called when the mouse's scroll wheel is scrolled up or down. This modifies the zoomFactor
which renders the graphics closer or further away on the screen. It also translates the graphics
slightly based on the position of the mouse. This creates an effect of zooming to the location
of the mouse on the screen.
"""
scrolledUp = event.GetWheelRotation() # Returns positive for up, negative for down
self.x, self.y = event.GetPosition()
viewport = glGetIntegerv(GL_VIEWPORT)
width = viewport[2]
height = viewport[3]
centerX = width / 2.0
centerY = height / 2.0
# Make sure cursor is on the screen
if ((self.x > 0 and self.x < width) and (self.y > 0 and self.y < height)):
if (scrolledUp > 0):
self.zoomFactor -= 2.0
self.translation[0] -= (self.x - centerX)
self.translation[1] += (self.y - centerY)
else:
self.zoomFactor += 2.0
self.translation[0] += (self.x - centerX)
self.translation[1] += (self.y - centerY)
if (self.zoomFactor > 150.0):
self.zoomFactor = 150.0
elif (self.zoomFactor < 0.1):
self.zoomFactor = 0.1
self.Refresh(False)
然后，您只需要翻译图形，设置视角，然后渲染场景。
# Translate graphics
glTranslatef(0.0, 0.0, (self.translation[1]/100.0) * (math.tan(self.cameraPosition[0]/self.cameraPosition[1])))
glTranslatef(0.0, (self.translation[0]/100.0) * (math.tan(self.cameraPosition[0]/self.cameraPosition[1])), 0.0)
# Set Perspective
glMatrixMode(GL_PROJECTION)
glLoadIdentity()
gluPerspective(self.zoomFactor, float(width)/float(height), self.nearPlane, self.farPlane)
# Render Scene
glMatrixMode(GL_MODELVIEW)
...Draw stuff here...