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我剛開始學習OpenGL for Android，繪製線條時出現奇怪的問題。我想要做的就是根據手指動作繪製一條線。現在，只要我開始刷卡，我總是會從原點（0,0）開始出現一條線條。基於運動的OpenGL ES 2.0繪圖線，線始終始於原點
這裏一個圖：
http://imageshack.us/photo/my-images/137/screenshot2012061312174.jpg/
箭頭符號我的手指運動，並在原點（紅圈）啓動線是提到線如下因素我的整個運動。
不要被Coords數組困擾我知道這不是最佳實踐，但是我冒充了整個程序並且無法找到涉及這個數組的任何錯誤。
我可能應該提及ArrayList點包含我所有生成的點。
我想摸不着頭腦，現在退出一段時間，但我真的堅持任何建議可能是有益的
這是我的整個呈現類。
公共類HelloOpenGLES20Renderer實現GLSurfaceView.Renderer {
private FloatBuffer triangleVB;
private int mProgram;
private int maPositionHandle;
public ArrayList<PointWrapper> points;
private int muMVPMatrixHandle;
private float[] mMVPMatrix = new float[16];
private float[] mMMatrix = new float[16];
private float[] mVMatrix = new float[16];
private float[] mProjMatrix = new float[16];
private int[] viewport = new int[4];
private ArrayList<Float> coordinates;
float[] Coords = new float[100000];
boolean first;
private int counter;
private PointWrapper last;
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; \n" +
"attribute vec4 vPosition; \n" + "void main(){ \n" +
// the matrix must be included as a modifier of gl_Position
" gl_Position = uMVPMatrix * vPosition; \n" +
"} \n";
private final String fragmentShaderCode = "precision mediump float; \n"
+ "void main(){ \n"
+ " gl_FragColor = vec4 (0.63671875, 0.76953125, 0.22265625, 1.0); \n"
+ "} \n";
private 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 HelloOpenGLES20Renderer() {
points = new ArrayList<PointWrapper>();
first = true;
this.counter = 0;
last = new PointWrapper();
coordinates = new ArrayList<Float>();
}
private float[] convertCoordinates(PointWrapper f) {
float[] vector = new float[4];
GLU.gluUnProject(f.point.x, f.point.y, 0.0f, mVMatrix, 0, mProjMatrix,
0, viewport, 0, vector, 0);
return vector;
}
private void initShapes() {
ArrayList<PointWrapper> points2 = new ArrayList<PointWrapper>(points);
float[] vector;
if (!points2.isEmpty()) {
if(points2.size()%2==1){
points2.remove(points2.size()-1);
}
for (int i = counter/2; i < points2.size(); i++) {
vector = convertCoordinates(points2.get(i));
Coords[counter] = vector[0]/vector[3];
Coords[counter+1] = -1 * (vector[1]/vector[3]);
counter= counter+2;
}
}
// initialize vertex Buffer for triangle
ByteBuffer vbb = ByteBuffer.allocateDirect(
// (# of coordinate values * 4 bytes per float)
Coords.length * 4);
vbb.order(ByteOrder.nativeOrder());// use the device hardware's native
// byte order
triangleVB = vbb.asFloatBuffer(); // create a floating point buffer from
// the ByteBuffer
triangleVB.put(Coords); // add the coordinates to the
// FloatBuffer
triangleVB.position(0); // set the buffer to read the first coordinate
}
public void onSurfaceCreated(GL10 unused, EGLConfig config) {
// Set the background frame color
GLES20.glClearColor(0.5f, 0.5f, 0.5f, 1.0f);
// initialize the triangle vertex array
// initShapes();
int vertexShader = loadShader(GLES20.GL_VERTEX_SHADER, vertexShaderCode);
int fragmentShader = 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); // creates OpenGL program executables
// get handle to the vertex shader's vPosition member
maPositionHandle = GLES20.glGetAttribLocation(mProgram, "vPosition");
}
public void onDrawFrame(GL10 unused) {
// Redraw background color
GLES20.glClear(GLES20.GL_COLOR_BUFFER_BIT | GLES20.GL_DEPTH_BUFFER_BIT);
initShapes();
// Add program to OpenGL environment
GLES20.glUseProgram(mProgram);
// Prepare the triangle data
GLES20.glVertexAttribPointer(maPositionHandle, 2, GLES20.GL_FLOAT,
false, 0, triangleVB);
GLES20.glEnableVertexAttribArray(maPositionHandle);
// Apply a ModelView Projection transformation
Matrix.multiplyMM(mMVPMatrix, 0, mProjMatrix, 0, mVMatrix, 0);
GLES20.glUniformMatrix4fv(muMVPMatrixHandle, 1, false, mMVPMatrix, 0);
GLES20.glLineWidth(5f);
GLES20.glDrawArrays(GLES20.GL_LINE_STRIP, 0, counter);
}
public void onSurfaceChanged(GL10 unused, int width, int height) {
GLES20.glViewport(0, 0, width, height);
float ratio = (float) width/height;
viewport[0] = 0;
viewport[1] = 0;
viewport[2] = width;
viewport[3] = height;
// this projection matrix is applied to object coodinates
// in the onDrawFrame() method
Matrix.frustumM(mProjMatrix, 0, -ratio, ratio, -1, 1, 3, 7);
muMVPMatrixHandle = GLES20.glGetUniformLocation(mProgram, "uMVPMatrix");
Matrix.setLookAtM(mVMatrix, 0, 0, 0, -3, 0f, 0f, 0f, 0f, 1.0f, 0.0f);
}
}
我在此先感謝
你能告訴'Coords'的內容？ –