java - 将 android-opengl 上的触摸转换为射线/矢量并检查它是否击中平面
问题描述
我对 Android 应用程序开发/使用 OpenGL ES 相当陌生。我的基本目标是在我的 Surface View 中创建 4 个简单的正方形，当用户单击屏幕时，我想检查他单击了哪些正方形（如果有）。当用户点击第二个（不同的）正方形时，这个正方形应该被标记并改变它的颜色，我想画一个从 square1 到 square2 的箭头。我使用opengl es 的 android 教程作为起点，并尝试根据我的目的对其进行调整。
我在检查用户是否点击了一个矩形时遇到了问题。我研究了很多关于 Android 中的 opengl 和一般线性代数的 stackoverflow 问题和其他指南。我发现这些是最有用的：
Opengl Tutorial
Mouse Picking with ray Casting
实现 Ray Picking
这是我到目前为止得到的结果：
我渲染的正方形是在模型-视图-投影矩阵中定义的，以便检查是否用户点击了这些正方形，我必须将点击转换为世界空间坐标中的射线。之后，我将不得不检查这条射线是否与我的正方形相撞，它们都位于同一平面上。
这是我编辑最多的地方，在surfaceCreated 上我添加了四个正方形并将它们移动到它们的位置。当用户点击屏幕时，checkCollision使用绝对屏幕坐标调用 -Method。我当时尝试的是翻译这些帖子中的说明：
实现线和平面的光线拾取
相交
public class MyGLRenderer implements GLSurfaceView.Renderer {
private static final String TAG = "MyGLRenderer";
private HashMap<String, Square> mySquares = new HashMap<>();
// mMVPMatrix is an abbreviation for "Model View Projection Matrix"
private final float[] mMVPMatrix = new float[16];
private final float[] mProjectionMatrix = new float[16];
private final float[] mViewMatrix = new float[16];
private final float[] mRotationMatrix = new float[16];
private int screenWidth = 0;
private int screenHeight = 0;
private float mAngle;
private int square_number = 65;
private final float[][] colors = {
{0.29f, 0.57f, 1.0f, 1.0f},
{0.8f, 0.0f, 0.0f, 1.0f},
{0.13f, 0.8f, 0.0f, 1.0f},
{1.0f, 0.84f, 0.0f, 1.0f}};
public void onSurfaceCreated(GL10 unused, EGLConfig config) {
// Set the background frame color
GLES20.glClearColor(1.0f, 1.0f, 1.0f, 1.0f);
//Adding the 4 squares to the grid and move them to their positions
String square_key = "";
square_key = addSquare();
this.mySquares.get(square_key).moveSquare(0.5f, 0.5f);
square_key = addSquare();
this.mySquares.get(square_key).moveSquare(0.5f, -0.5f);
square_key = addSquare();
this.mySquares.get(square_key).moveSquare(-0.5f, 0.5f);
square_key = addSquare();
this.mySquares.get(square_key).moveSquare(-0.5f, -0.5f);
}
public void checkCollision(float touchX, float touchY) {
//Step 1: normalize coordinates
float[] touchClipMatrix = new float[]{
2.0f * touchX / this.screenWidth - 1.0f,
1.0f - touchY * 2 / this.screenHeight,
0,
1.0f
};
//inverted matrices
float[] invertedProjectionMatrix = new float[16];
float[] invertedMViewMatrix = new float[16];
Matrix.invertM(invertedProjectionMatrix,0, mProjectionMatrix, 0);
Matrix.invertM(invertedMViewMatrix,0, mViewMatrix, 0);
//Calculation Matrices
float[] unviewMatrix = new float[16];
float[] mouse_worldspace = new float[4];
//Getting mouse position in world space
Matrix.multiplyMM(unviewMatrix, 0, invertedMViewMatrix, 0, invertedProjectionMatrix,0);
Matrix.multiplyMV(mouse_worldspace, 0 , unviewMatrix, 0 , touchClipMatrix, 0);
Log.i(TAG, "checkCollision-touchClipMatrix: "+ Arrays.toString(touchClipMatrix));
Log.i(TAG, "checkCollision-invertedProjectionMatrix: "+ Arrays.toString(invertedProjectionMatrix));
Log.i(TAG, "checkCollision-invertedMViewMatrix: "+ Arrays.toString(invertedMViewMatrix));
Log.i(TAG, "checkCollision-mouse_worldspace: "+ Arrays.toString(mouse_worldspace));
//Getting the camera position
float [] cameraPosition = {0, 0, -3};
//subtract camera position from the mouse_worldspace
float [] ray_unnormalized = new float[4];
for(int i = 0; i < 3; i++){
ray_unnormalized[i] = mouse_worldspace[i] / mouse_worldspace[3] - cameraPosition[i];
}
//normalize ray_vector
float ray_length = Matrix.length(ray_unnormalized[0], ray_unnormalized[1], ray_unnormalized[2]);
float [] ray_vector = new float[4];
for(int i=0; i<3; i++){
ray_vector[i] = ray_unnormalized[i]/ray_length;
}
Log.i(TAG, "checkCollision - ray_vector: "+ Arrays.toString(ray_vector));
LinePlaneIntersection linePlaneIntersection = new LinePlaneIntersection();
LinePlaneIntersection.Vector3D rv = new LinePlaneIntersection.Vector3D(ray_vector[0], ray_vector[1], ray_vector[2]);
LinePlaneIntersection.Vector3D rp = new LinePlaneIntersection.Vector3D(mouse_worldspace[0], mouse_worldspace[1], mouse_worldspace[2]);
LinePlaneIntersection.Vector3D pn = new LinePlaneIntersection.Vector3D(0.0, 0.0, 0.0);
LinePlaneIntersection.Vector3D pp = new LinePlaneIntersection.Vector3D(0.0, 0.0, 1.0);
LinePlaneIntersection.Vector3D ip = linePlaneIntersection.intersectPoint(rv, rp, pn, pp);
Log.i(TAG, "checkCollision-intersection point: "+ip);
}
public String addSquare() {
String keyName = String.valueOf((char) this.square_number);
this.mySquares.put(keyName, new Square(keyName, colors[this.square_number-65]));
this.square_number += 1;
return keyName;
}
public void logMatrices() {
Log.i(TAG, "MVPMatrice: " + Arrays.toString(this.mMVPMatrix));
Log.i(TAG, "mProjectionMarice: " + Arrays.toString(this.mProjectionMatrix));
Log.i(TAG, "mViewMatrice: " + Arrays.toString(this.mViewMatrix));
}
@Override
public void onDrawFrame(GL10 unused) {
float[] scratch = new float[16];
// Draw background color
GLES20.glClear(GLES20.GL_COLOR_BUFFER_BIT | GLES20.GL_DEPTH_BUFFER_BIT);
// Set the camera position (View matrix)
//mySquare.moveSquare(0.25f, 0.25f);
Matrix.setLookAtM(mViewMatrix, 0, 0, 0, -3, 0f, 0f, 0.0f, 0f, 1.0f, 0.0f);
// Matrix.scaleM(mViewMatrix, 0, 0.5f,0.5f,0);
// Matrix.translateM(mViewMatrix, 0, 2f, 1f, 0);
// Calculate the projection and view transformation
Matrix.multiplyMM(mMVPMatrix, 0, mProjectionMatrix, 0, mViewMatrix, 0);
// Create a rotation for the square
Matrix.setRotateM(mRotationMatrix, 0, mAngle, 0, 0.0f, 1.0f);
// Combine the rotation matrix with the projection and camera view
// Note that the mMVPMatrix factor *must be first* in order
// for the matrix multiplication product to be correct.
Matrix.multiplyMM(scratch, 0, mMVPMatrix, 0, mRotationMatrix, 0);
// Draw squares
for (Map.Entry<String, Square> s : this.mySquares.entrySet()) {
s.getValue().draw(scratch);
}
}
@Override
public void onSurfaceChanged(GL10 unused, int width, int height) {
this.screenWidth = width;
this.screenHeight = height;
// Adjust the viewport based on geometry changes,
// such as screen rotation
GLES20.glViewport(0, 0, width, height);
float ratio = (float) width / height;
// this projection matrix is applied to object coordinates
// in the onDrawFrame() method
Matrix.frustumM(mProjectionMatrix, 0, -ratio, ratio, -1, 1, 3, 7);
}
public static int loadShader(int type, String shaderCode) {
// create a vertex shader type (GLES20.GL_VERTEX_SHADER)
// or a fragment shader type (GLES20.GL_FRAGMENT_SHADER)
int shader = GLES20.glCreateShader(type);
// add the source code to the shader and compile it
GLES20.glShaderSource(shader, shaderCode);
GLES20.glCompileShader(shader);
return shader;
}
public static void checkGlError(String glOperation) {
int error;
while ((error = GLES20.glGetError()) != GLES20.GL_NO_ERROR) {
Log.e(TAG, glOperation + ": glError " + error);
throw new RuntimeException(glOperation + ": glError " + error);
}
}
}
我添加了一个 moveSquare-Methode，因为所有的正方形在初始化时都有相同的坐标。我不确定这是否是正确的方法，请告诉我这是否错误/弄乱了其他计算。
public class Square {
private String squareID;
private final String vertexShaderCode =
// This matrix member variable provides a hook to manipulate
// the coordinates of the objects that use this vertex shader
"uniform mat4 uMVPMatrix;" +
"attribute vec4 squarePosition;" +
"void main() {" +
// The matrix must be included as a modifier of gl_Position.
// Note that the uMVPMatrix factor *must be first* in order
// for the matrix multiplication product to be correct.
" gl_Position = uMVPMatrix * squarePosition;" +
"}";
private final String fragmentShaderCode =
"precision mediump float;" +
"uniform vec4 squareColor;" +
"void main() {" +
" gl_FragColor = squareColor;" +
"}";
private FloatBuffer vertexBuffer;
private ShortBuffer drawListBuffer;
private int mProgram;
private int mPositionHandle;
private int mColorHandle;
private int mMVPMatrixHandle;
private static final String TAG = "Square";
// number of coordinates per vertex in this array
static final int COORDS_PER_VERTEX = 3;
private float squareCoords[] = {
-0.1f, 0.1f, 0.0f, // top left
-0.1f, -0.1f, 0.0f, // bottom left
0.1f, -0.1f, 0.0f, // bottom right
0.1f, 0.1f, 0.0f}; // top right
private final short drawOrder[] = {0, 1, 2, 0, 2, 3}; // order to draw vertices
private final int vertexStride = COORDS_PER_VERTEX * 4; // 4 bytes per vertex
//Fallback color
private float color[] = {0.2f, 0.709803922f, 0.898039216f, 1.0f};
/**
* Sets up the drawing object data for use in an OpenGL ES context.
*/
public Square(String id, float [] color) {
this.squareID = id;
if(color.length == 4) {
this.color = color;
}
//Buffers need to updated with the new square coordinates
updateBuffers();
//Shaders (should) only be prepared once when initializing a square
prepareShadersAndOpenGL();
}
private void prepareShadersAndOpenGL() {
// prepare shaders and OpenGL program
int vertexShader = MyGLRenderer.loadShader(
GLES20.GL_VERTEX_SHADER,
vertexShaderCode);
int fragmentShader = MyGLRenderer.loadShader(
GLES20.GL_FRAGMENT_SHADER,
fragmentShaderCode);
mProgram = GLES20.glCreateProgram(); // create empty OpenGL Program
GLES20.glAttachShader(mProgram, vertexShader); // add the vertex shader to program
GLES20.glAttachShader(mProgram, fragmentShader); // add the fragment shader to program
GLES20.glLinkProgram(mProgram); // create OpenGL program executables
}
public void updateBuffers() {
// initialize vertex byte buffer for shape coordinates
ByteBuffer bb = ByteBuffer.allocateDirect(
// (# of coordinate values * 4 bytes per float)
squareCoords.length * 4);
bb.order(ByteOrder.nativeOrder());
vertexBuffer = bb.asFloatBuffer();
vertexBuffer.put(squareCoords);
vertexBuffer.position(0);
// initialize byte buffer for the draw list
ByteBuffer dlb = ByteBuffer.allocateDirect(
// (# of coordinate values * 2 bytes per short)
drawOrder.length * 2);
dlb.order(ByteOrder.nativeOrder());
drawListBuffer = dlb.asShortBuffer();
drawListBuffer.put(drawOrder);
drawListBuffer.position(0);
}
//Updating the square coordinates and updating to buffers
public void moveSquare(float deltaX, float deltaY) {
this.squareCoords[0] += deltaX;
this.squareCoords[3] += deltaX;
this.squareCoords[6] += deltaX;
this.squareCoords[9] += deltaX;
this.squareCoords[1] += deltaY;
this.squareCoords[4] += deltaY;
this.squareCoords[7] += deltaY;
this.squareCoords[10] += deltaY;
updateBuffers();
}
/**
* Encapsulates the OpenGL ES instructions for drawing this shape.
*
* @param mvpMatrix - The Model View Project matrix in which to draw
* this shape.
*/
public void draw(float[] mvpMatrix) {
// Add program to OpenGL environment
// Log.i(TAG, "Square ("+squareID+") mProgram: "+mProgram);
GLES20.glUseProgram(mProgram);
// get handle to vertex shader's vPosition member
mPositionHandle = GLES20.glGetAttribLocation(mProgram, "squarePosition");
// Enable a handle to the triangle vertices
GLES20.glEnableVertexAttribArray(mPositionHandle);
// Prepare the triangle coordinate data
GLES20.glVertexAttribPointer(
mPositionHandle, COORDS_PER_VERTEX,
GLES20.GL_FLOAT, false,
vertexStride, vertexBuffer);
// get handle to fragment shader's vColor member
mColorHandle = GLES20.glGetUniformLocation(mProgram, "squareColor");
// Set color for drawing the triangle
GLES20.glUniform4fv(mColorHandle, 1, color, 0);
// get handle to shape's transformation matrix
mMVPMatrixHandle = GLES20.glGetUniformLocation(mProgram, "uMVPMatrix");
// MyGLRenderer.checkGlError("glGetUniformLocation");
// Apply the projection and view transformation
GLES20.glUniformMatrix4fv(mMVPMatrixHandle, 1, false, mvpMatrix, 0);
// MyGLRenderer.checkGlError("glUniformMatrix4fv");
// Draw the square
GLES20.glDrawElements(
GLES20.GL_TRIANGLES, drawOrder.length,
GLES20.GL_UNSIGNED_SHORT, drawListBuffer);
// Disable vertex array
GLES20.glDisableVertexAttribArray(mPositionHandle);
}
}
public class MyGLSurfaceView extends GLSurfaceView {
private final MyGLRenderer mRenderer;
private static final String TAG = "MyGLSurfaceView";
private final float TOUCH_SCALE_FACTOR = 180.0f / 320;
public MyGLSurfaceView(Context context) {
super(context);
// Create an OpenGL ES 2.0 context.
setEGLContextClientVersion(2);
// Set the Renderer for drawing on the GLSurfaceView
mRenderer = new MyGLRenderer();
setRenderer(mRenderer);
// Render the view only when there is a change in the drawing data
setRenderMode(GLSurfaceView.RENDERMODE_WHEN_DIRTY);
}
@Override
public boolean onTouchEvent(MotionEvent e) {
// MotionEvent reports input details from the touch screen
// and other input controls. In this case, you are only
// interested in events where the touch position changed.
float x = e.getX();
float y = e.getY();
switch (e.getAction()) {
case MotionEvent.ACTION_DOWN:
mRenderer.logMatrices();
mRenderer.checkCollision(x, y);
// mRenderer.setAngle(mRenderer.getAngle()+45f);
requestRender();
}
return true;
}
}
我知道这需要阅读很多内容，因此我将尝试表达我的主要问题/问题：
- 我的想法总体上是正确的还是我使用了错误的转换/步骤？
- Square-类中的 squareCoord-Array 是否代表我的模型矩阵，在什么时候将它们转换为世界坐标？
- 为什么我给 square-class 中的 draw-Method 的矩阵称为 mMVPMatrix，对我来说，这意味着该矩阵包含所有三个矩阵（模型、视图、投影）。但是在我调用draw-Method的时候，我刚刚将Projection-与View-Matrix相乘，那么Model-Part应该从哪里来呢？我在这里遗漏了什么还是我混淆了矩阵的术语？
- 我仍在尝试了解 Projection-Matrix 的作用/描述。我知道它基本上定义了要渲染的区域，不在这个区域内的所有内容都不会显示在屏幕上。这个区域是否总是相对于相机（视图）位置？
我希望我正确地解释了我的问题，也许一般来说我的问题甚至有更简单的解决方案。提前感谢所有到目前为止阅读的人。我希望有人可以帮助我
PS：这是我在 Stackoverflow 上的第一个问题，我的拼写可能不完美，很抱歉。如果您缺少了解问题的信息/回答我刚刚提出的问题之一，我将尝试尽快添加它们。
以下是一些调试信息：
- 已识别位置 x=940.94604| 上的触摸 y=407.9297
- MVP 矩阵：[-4.4, 0.0, 0.0, 0.0, 0.0, 3.0, 0.0, 0.0, 0.0, 0.0, 2.5, 1.0, 0.0, 0.0, -3.0, 3.0]
- mProjectionMarix: [4.4, 0.0, 0.0, 0.0, 0.0, 3.0, 0.0, 0.0, 0.0, 0.0, -2.5, -1.0, 0.0, 0.0, -10.5, 0.0]
- mViewMatrix: [-1.0, 0.0, -0.0, 0.0, 0.0, 1.0, -0.0, 0.0, 0.0, -0.0, -1.0, 0.0, 0.0, 0.0, -3.0, 1.0]
- checkCollision-touchClipMatrix: [0.7424927, 0.48493725, -3.0, 1.0]
- checkCollision-invertedProjectionMatrix: [0.22727272, -0.0, -0.0, -0.0, -0.0, 0.3333333, -0.0, -0.0, -0.0, -0.0, -0.0, -0.0952381, -0.0, -0.0, -1.0, 0.23809522]
- checkCollision-invertedMViewMatrix: [-1.0, 0.0, 0.0, 0.0, 0.0, 1.0, 0.0, 0.0, 0.0, 0.0, -1.0, 0.0, 0.0, -0.0, -3.0, 1.0]
- checkCollision-unview-Matrix[-0.22727272, 0.0, 0.0, 0.0, 0.0, 0.3333333, 0.0, 0.0, 0.0, 0.0, 0.2857143, -0.0952381, 0.0, -0.0, 0.28571423, 0.2380952
- checkCollision-mouse_worldspace: [-0.16874833, 0.16164574, -0.5714286, 0.52380955]
- checkCollision-ray_unnormalized: [-0.3221559, 0.3085964, 1.9090909, 0.0]
- checkCollision-ray_length：1.9605213
- checkCollision - ray_vector: [-0.16432154, 0.15740527, 0.9737669, 0.0]
- checkCollision-intersection point: (NaN, NaN, NaN)
解决方案
的计算ray_unnormalized似乎是错误的。您不能以您的方式减去齐次坐标。将mouse_worldspace转换为笛卡尔坐标。笛卡尔坐标是x 、 y和z分量与w分量的商（参见透视除法）。
射线方向是从笛卡尔相机位置到笛卡尔鼠标位置的矢量：
//Getting the camera position
float [] cameraPosition = {0, 0, -6};
//subtract camera position from the mouse_worldspace
float [] ray_unnormalized = new float[4];
for(int i = 0; i < 3; i++){
ray_unnormalized[i] = mouse_worldspace[i] / mouse_worldspace[3] - cameraPosition[i];
}
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