android - 在 Android 上使用 opengl es 2.0 进行简单翻译

Question

我到处寻找如何使用 openGl es 2.0 翻译形状，但找不到正确的方法。旋转和缩放工作正常。

我用 android openGl es 2.0 教程尝试过，但形状比平移的更扭曲。

这是代码(几乎与 android 代码示例 http://developer.android.com/shareables/training/OpenGLES.zip 相同，除了要翻译的行:

public class MyGLRenderer implements GLSurfaceView.Renderer {

    private static final String TAG = "MyGLRenderer";
    private Triangle mTriangle;
    private Square   mSquare;

    private final float[] mMVPMatrix = new float[16];
    private final float[] mProjMatrix = new float[16];
    private final float[] mVMatrix = new float[16];
    private final float[] mRotationMatrix = new float[16];

    // Declare as volatile because we are updating it from another thread
    public volatile float mAngle;

    @Override
    public void onSurfaceCreated(GL10 unused, EGLConfig config) {

        // Set the background frame color
        GLES20.glClearColor(0.0f, 0.0f, 0.0f, 1.0f);

        mTriangle = new Triangle();
        mSquare   = new Square();
    }

    @Override
    public void onDrawFrame(GL10 unused) {

        // Draw background color
        GLES20.glClear(GLES20.GL_COLOR_BUFFER_BIT);

        // Set the camera position (View matrix)
        Matrix.setLookAtM(mVMatrix, 0, 0, 0, -3, 0f, 0f, 0f, 0f, 1.0f, 0.0f);

        // Calculate the projection and view transformation
        Matrix.multiplyMM(mMVPMatrix, 0, mProjMatrix, 0, mVMatrix, 0);

        // Draw square
        mSquare.draw(mMVPMatrix);

        // Create a rotation for the triangle
//        long time = SystemClock.uptimeMillis() % 4000L;
//        float angle = 0.090f * ((int) time);
        Matrix.setRotateM(mRotationMatrix, 0, mAngle, 0, 0, -1.0f);

        // Combine the rotation matrix with the projection and camera view
        Matrix.multiplyMM(mMVPMatrix, 0, mRotationMatrix, 0, mMVPMatrix, 0);

        // Draw triangle
        mTriangle.draw(mMVPMatrix);
    }

    @Override
    public void onSurfaceChanged(GL10 unused, int width, int 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(mProjMatrix, 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;
    }

    /**
     * Utility method for debugging OpenGL calls. Provide the name of the call
     * just after making it:
     *
     * <pre>
     * mColorHandle = GLES20.glGetUniformLocation(mProgram, "vColor");
     * MyGLRenderer.checkGlError("glGetUniformLocation");</pre>
     *
     * If the operation is not successful, the check throws an error.
     *
     * @param glOperation - Name of the OpenGL call to check.
     */
    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);
        }
    }
}

这是带有平移转换的 square 类:

class Square {

    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 vPosition;" +
        "void main() {" +
        // the matrix must be included as a modifier of gl_Position
        "  gl_Position = vPosition * uMVPMatrix;" +
        "}";

    private final String fragmentShaderCode =
        "precision mediump float;" +
        "uniform vec4 vColor;" +
        "void main() {" +
        "  gl_FragColor = vColor;" +
        "}";

    private final FloatBuffer vertexBuffer;
    private final ShortBuffer drawListBuffer;
    private final int mProgram;
    private int mPositionHandle;
    private int mColorHandle;
    private int mMVPMatrixHandle;

    // number of coordinates per vertex in this array
    static final int COORDS_PER_VERTEX = 3;
    static float squareCoords[] = { -0.5f,  0.5f, 0.0f,   // top left
                                    -0.5f, -0.5f, 0.0f,   // bottom left
                                     0.5f, -0.5f, 0.0f,   // bottom right
                                     0.5f,  0.5f, 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

    // Set color with red, green, blue and alpha (opacity) values
    float color[] = { 0.2f, 0.709803922f, 0.898039216f, 1.0f };

    public Square() {
        // 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);

        // 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 draw(float[] mvpMatrix) {
        // Add program to OpenGL environment
        GLES20.glUseProgram(mProgram);

        // get handle to vertex shader's vPosition member
        mPositionHandle = GLES20.glGetAttribLocation(mProgram, "vPosition");

        // 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, "vColor");

        // 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");


//TRANSLATION
        float[] transMatrix = new float[16];

        Matrix.setIdentityM(transMatrix,0);
        Matrix.translateM(transMatrix,0,5.0f,0,0);
        Matrix.multiplyMM(transMatrix,0,mvpMatrix,0,transMatrix,0);



        // Apply the projection and view transformation
        GLES20.glUniformMatrix4fv(mMVPMatrixHandle, 1, false, transMatrix, 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);
    }
}

我认为这与顶点着色器代码有关，但我无法弄清楚？

Answer 1

我正在渲染器的 onDrawFrame 方法中进行矩阵的转换，因此我的代码如下所示:

    // Set the camera position (View matrix)
    Matrix.setLookAtM(mViewMatrixS, 0, 0, 0, -3, 0f, 0f, 0f, 0f, 1.0f, 0.0f);

   //translate the Matrix
   Matrix.translateM(mViewMatrixS, 0, 2f, 1f, 0);

   // Calculate the projection and view transformation
   Matrix.multiplyMM(mMVPMatrixS, 0, mProjectionMatrix, 0, mViewMatrixS, 0);

   // Draw square
   mSquare.draw(mMVPMatrix);

这可以正确翻译我的形状。不知道是不是这个问题。