我正在构建一个使用OpenGL ES 2.0的Android应用程序,而且我遇到了障碍。我试图将屏幕坐标(用户触摸的位置)转换为世界坐标。我已经尝试过阅读和玩弄GLU.gluUnProject但是我做错了或者只是不理解它。
这是我的尝试......
public void getWorldFromScreen(float x, float y) {
int viewport[] = { 0, 0, width , height};
float startY = ((float) (height) - y);
float[] near = { 0.0f, 0.0f, 0.0f, 0.0f };
float[] far = { 0.0f, 0.0f, 0.0f, 0.0f };
float[] mv = new float[16];
Matrix.multiplyMM(mv, 0, mViewMatrix, 0, mModelMatrix, 0);
GLU.gluUnProject(x, startY, 0, mv, 0, mProjectionMatrix, 0, viewport, 0, near, 0);
GLU.gluUnProject(x, startY, 1, mv, 0, mProjectionMatrix, 0, viewport, 0, far, 0);
float nearX = near[0] / near[3];
float nearY = near[1] / near[3];
float nearZ = near[2] / near[3];
float farX = far[0] / far[3];
float farY = far[1] / far[3];
float farZ = far[2] / far[3];
}
我得到的数字似乎不对,这是使用这种方法的正确方法吗?它适用于OpenGL ES 2.0吗?我应该在这些计算之前将模型矩阵设为单位矩阵(Matrix.setIdentityM(mModelMatix,0))吗?
作为跟进,如果这是正确的,我如何选择输出Z?基本上,我总是知道我希望世界坐标处于什么距离,但GLU.gluUnProject中的Z参数似乎是近平面和远平面之间的某种插值。它只是一个线性插值吗?
提前致谢
答案 0 :(得分:22)
/**
* Calculates the transform from screen coordinate
* system to world coordinate system coordinates
* for a specific point, given a camera position.
*
* @param touch Vec2 point of screen touch, the
actual position on physical screen (ej: 160, 240)
* @param cam camera object with x,y,z of the
camera and screenWidth and screenHeight of
the device.
* @return position in WCS.
*/
public Vec2 GetWorldCoords( Vec2 touch, Camera cam)
{
// Initialize auxiliary variables.
Vec2 worldPos = new Vec2();
// SCREEN height & width (ej: 320 x 480)
float screenW = cam.GetScreenWidth();
float screenH = cam.GetScreenHeight();
// Auxiliary matrix and vectors
// to deal with ogl.
float[] invertedMatrix, transformMatrix,
normalizedInPoint, outPoint;
invertedMatrix = new float[16];
transformMatrix = new float[16];
normalizedInPoint = new float[4];
outPoint = new float[4];
// Invert y coordinate, as android uses
// top-left, and ogl bottom-left.
int oglTouchY = (int) (screenH - touch.Y());
/* Transform the screen point to clip
space in ogl (-1,1) */
normalizedInPoint[0] =
(float) ((touch.X()) * 2.0f / screenW - 1.0);
normalizedInPoint[1] =
(float) ((oglTouchY) * 2.0f / screenH - 1.0);
normalizedInPoint[2] = - 1.0f;
normalizedInPoint[3] = 1.0f;
/* Obtain the transform matrix and
then the inverse. */
Print("Proj", getCurrentProjection(gl));
Print("Model", getCurrentModelView(gl));
Matrix.multiplyMM(
transformMatrix, 0,
getCurrentProjection(gl), 0,
getCurrentModelView(gl), 0);
Matrix.invertM(invertedMatrix, 0,
transformMatrix, 0);
/* Apply the inverse to the point
in clip space */
Matrix.multiplyMV(
outPoint, 0,
invertedMatrix, 0,
normalizedInPoint, 0);
if (outPoint[3] == 0.0)
{
// Avoid /0 error.
Log.e("World coords", "ERROR!");
return worldPos;
}
// Divide by the 3rd component to find
// out the real position.
worldPos.Set(
outPoint[0] / outPoint[3],
outPoint[1] / outPoint[3]);
return worldPos;
}
进一步解释了算法here.
答案 1 :(得分:1)
希望我的问题(和答案)可以帮助你:
How to find absolute position of click while zoomed in
它不仅有代码,还有解释它的图表,图表和图表:)我花了很多时间来弄清楚它。
答案 2 :(得分:1)
恕我直言,不需要重新实现此功能...... 我试用了Erol的解决方案并且它有效,所以非常感谢Erol。 此外,我玩
Matrix.orthoM(mtrxProjection, 0, left, right, bottom, top, near, far);
并且在我的微型noob示例2D OpenGL ES 2.0项目中也可以正常工作: