Question

我正在尝试遵循Android开发人员的“使用OpenGL ES显示图形”教程。在第一部分中，我必须绘制一个三角形，并且一切正常。现在，我应该通过使用Square类来绘制一个正方形，该类可以按照本教程进行定义。当我尝试绘制（使用我通常从Triangle类复制的draw（）方法）时，屏幕上仅显示一个三角形，该三角形是定义的正方形的一半（显然，我已经注释掉了triangle.draw（）行。）。

这是我的代码，有人提示您解决吗？

Square.java：

public class Square {

    private FloatBuffer vertexBuffer;
    private ShortBuffer drawListBuffer;

    private final int mProgram;

    private final String vertexShaderCode =
            "attribute vec4 vPosition;" +
                    "void main() {" +
                    "  gl_Position = vPosition;" +
                    "}";

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

    // 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

    // Set color with red, green, blue and alpha (opacity) values
    float color[] = { 0.63671875f, 0.76953125f, 0.22265625f, 1.0f };

    private short drawOrder[] = { 0, 1, 2, 0, 2, 3 }; // order to draw vertices

    public Square() {
        // initialize vertex byte buffer for shape coordinates
        ByteBuffer bb = ByteBuffer.allocateDirect(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(drawOrder.length * 2);
        dlb.order(ByteOrder.nativeOrder());
        drawListBuffer = dlb.asShortBuffer();
        drawListBuffer.put(drawOrder);
        drawListBuffer.position(0);

        int vertexShader = MyGLRenderer.loadShader(GLES20.GL_VERTEX_SHADER,
                vertexShaderCode);
        int fragmentShader = MyGLRenderer.loadShader(GLES20.GL_FRAGMENT_SHADER,
                fragmentShaderCode);

        // create empty OpenGL ES Program
        mProgram = GLES20.glCreateProgram();

        // add the vertex shader to program
        GLES20.glAttachShader(mProgram, vertexShader);

        // add the fragment shader to program
        GLES20.glAttachShader(mProgram, fragmentShader);

        // creates OpenGL ES program executables
        GLES20.glLinkProgram(mProgram);
    }

    private int mPositionHandle;
    private int mColorHandle;

    private final int vertexCount = squareCoords.length / COORDS_PER_VERTEX;
    private final int vertexStride = COORDS_PER_VERTEX * 4; // 4 bytes per vertex

    public void draw() {
        // Add program to OpenGL ES 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);

        // Draw the square
        GLES20.glDrawArrays(GLES20.GL_TRIANGLES, 0, vertexCount);

        // Disable vertex array
        GLES20.glDisableVertexAttribArray(mPositionHandle);
    }
}

Answer 1

请参见Triangle primitives

您有4个顶点坐标，它们的排列方式如下：

handleClick(index){    
    if(this.state.player && !this.state.winner){    
      let newBoard = this.state.board    
      if(this.state.board[index]===null){    
        newBoard[index] = this.state.player    
        this.setState({
          board: newBoard,
          player: this.state.player==="X" ? "O" : "X"
        })    
        this.checkWinner()    
      }
    }
    setTimeout(() => {
       this.props.undoRedo.addStep();
    });
  }

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

此模式匹配原始类型0 3 x x | | | | x-----x 1 2，但不匹配原始类型GL_TRIANGLE_FAN。

更改原始类型以解决您的问题：

GL_TRIANGLES

请注意，对于基本类型GLES20.glDrawArrays(GLES20.GL_TRIANGLE_FAN, 0, vertexCount);，您需要6个顶点坐标，例如安排如下：

GL_TRIANGLES

原始类型0 3 5 x x-----x | \ \ | | \ \ | x-----x x 1 2 4与您的索引缓冲区匹配：

GL_TRIANGLES

如果要从索引列表中绘制基元，则必须使用glDrawElements：

private short drawOrder[] = { 0, 1, 2, 0, 2, 3 };

Open GL ES 2.0画一个正方形

1 个答案: