我正在尝试将pan和pinch-to-zoom功能实现到我拥有的OpenGL应用程序中。我能够使用简单的glTranslatef相对轻松地实现平移功能，但使用glScalef功能会带来更多困难。我有三个类，一个用于GLSurfaceView，一个用于GLTriangle，第三个用于GLRenderer，这是glScalef和{{1}使用。
glTranslatef上课：
GLRenderer public class GLRendererEx implements Renderer, OnTouchListener {
private GLTriangleEx tri;
float ratio;
float x = 0, y = 0;
float dx = 0, dy = 0;
float sx = 0, sy = 0;
float tx = 0, ty = 0;
float xtwo = 0, ytwo = 0;
float sxtwo = 0, sytwo = 0;
float screenX, screenY;
float xscale = 1, yscale = 1;
float xscaletwo = 1;
float xscaletotal = 1, yscaletotal = 1;
int NONE = 0, DRAG = 1, ZOOM = 2;
int mode = NONE;
int width, height;
boolean touched = true;
Display getOrient = getWindowManager().getDefaultDisplay();
int orientation;
public GLRendererEx() {
tri = new GLTriangleEx();
screenX = ourSurface.getWidth();
screenY = ourSurface.getHeight();
ourSurface.setOnTouchListener(this);
}
@Override
public void onSurfaceCreated(GL10 gl, EGLConfig eglConfig) {
gl.glDisable(GL10.GL_DITHER);
gl.glHint(GL10.GL_PERSPECTIVE_CORRECTION_HINT, GL10.GL_FASTEST);
gl.glClearColor(0f, 0f, 0f, 1f);
gl.glClearDepthf(1f);
orientation = getOrient.getRotation();
}
@Override
public void onDrawFrame(GL10 gl) {
gl.glClear(GL10.GL_COLOR_BUFFER_BIT | GL10.GL_DEPTH_BUFFER_BIT);
gl.glMatrixMode(GL10.GL_MODELVIEW);
gl.glLoadIdentity();
GLU.gluLookAt(gl, 0, 0, -5, 0, 0, 0, 0, 2, 0);
//warning - x is backwards
gl.glTranslatef(tx, ty, 0);
gl.glScalef(xscaletotal, yscaletotal, 1);
tri.draw(gl);
}
@Override
public void onSurfaceChanged(GL10 gl, int width, int height) {
gl.glViewport(0, 0, width, height);
ratio = ((float) width) / height;
screenX = width;
screenY = height;
orientation = getOrient.getRotation();
gl.glMatrixMode(GL10.GL_PROJECTION);
gl.glLoadIdentity();
gl.glFrustumf(-ratio, ratio, -1, 1, 1, 50);
}
@Override
public boolean onTouch(View v, MotionEvent event) {
switch (event.getAction()) {
case MotionEvent.ACTION_DOWN: {
event.getActionIndex();
sx = x = event.getX(0);
sy = y = event.getY(0);
mode = DRAG;
break;
}
case MotionEvent.ACTION_POINTER_DOWN: {
event.getActionIndex();
sxtwo = xtwo = event.getX(1);
sytwo = ytwo = event.getY(1);
mode = ZOOM;
touched = true;
break;
}
case MotionEvent.ACTION_MOVE: {
x = event.getX(0);
y = event.getY(0);
xtwo = event.getX(1);
ytwo = event.getY(1);
if (mode == ZOOM)
midPoint(x, y, xtwo, ytwo);
if (mode == DRAG) {
dx = x - sx;
dy = y - sy;
dx *= -8;
dy *= -8;
if (orientation == Configuration.ORIENTATION_LANDSCAPE)
dx *= 2;
dx /= screenX;
dy /= screenY;
tx += dx;
ty += dy;
sx = x;
sy = y;
}
break;
}
case MotionEvent.ACTION_POINTER_UP: {
mode = DRAG;
break;
}
case MotionEvent.ACTION_UP: {
mode = NONE;
break;
}
}
return true;
}
private float midPoint(float x, float y, float xtwo, float ytwo) {
x -= xtwo;
y -= ytwo;
if (touched) {
sxtwo = x;
sytwo = y;
xscaletwo = FloatMath.sqrt(sxtwo * sxtwo + sytwo * sytwo);
touched = false;
}
xscale -= xscaletwo;
xscale = FloatMath.sqrt(x * x + y * y);
xscaletotal += xscale;
yscaletotal = xscaletotal;
return xscale;
}
}
是坐标，x/y是坐标的变化，dx/dy是开始坐标，sx/sy是坐标的总变化（用于平移），tx/ty是用于计算缩放比例的浮点数，xscale/yscale是缩放比例的总变化，没有拖动缩放和模式代表模式。
就目前而言，我可以通过拉开手指来放大，但是捏也可以缩放而不是缩小。此外，变焦太敏感了。
我真的不知道如何从这里解决这个问题。任何帮助都不仅仅是值得赞赏的。
答案 0 :(得分：1)
看起来你的“midPoint”有一些工作要做..尝试做这样的事情：
float scale = 1.0; //factor used in glScalef
float previousPinchScale; //needed to remember from previous methode call
private float midPoint(float x, float y, float xtwo, float ytwo) {
float currentPinchScale = FloatMath.sqrt((x-xTwo)*(x-xTwo) + (y-yTwo)*(y-yTwo)); //current distance between both "touches"
if (touched) { //gesture just began:
previousPinchScale = currentPinchScale; //Save relative information about touch positions
touched = false;
}
else { //gesture in progress:
/*
At this point we have 2 values of "PinchScale" for this and previous "midPoint" method call.
The factor of relative change in this distance should be applied to current scene scale:
currentPinchScale/previousPinchScale is the "relative change", for instance if the distance between the 2 touches would be 10% this factor would return 1.1
Since we have to consider that scene might already be zoomed you need to take previous scale and multiply it with this change..
*/
scale *= currentPinchScale/previousPinchScale; //scale used in glScalef
previousPinchScale = currentPinchScale; //remember the new position of "midPoint" call
}
return scale;
}