OpenGL 2.0 为立方体设置不同的颜色

Question

我正在尝试使用 OpenGL ES 2.0 在每个面上绘制一个不同颜色的立方体。我现在只能用一种颜色画一个立方体。我知道在这种情况下我需要使用VertexAttribPointer 而不是Uniform，但我可能错误地添加了它们。实现代码后，屏幕不显示任何内容。这是我的代码，有人可以帮我一把吗？非常感谢！！！

public class MyCube {
private FloatBuffer vertexBuffer;
private ShortBuffer drawListBuffer;
private ShortBuffer[] ArrayDrawListBuffer;
private FloatBuffer colorBuffer;
private int mProgram;
//For Projection and Camera Transformations
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
                // Note that the uMVPMatrix factor *must be first* in order
                // for the matrix multiplication product to be correct.
                "  gl_Position = uMVPMatrix * vPosition;" +
                "}";
// Use to access and set the view transformation
private int mMVPMatrixHandle;
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;
float cubeCoords[] = {
        -0.5f, 0.5f, 0.5f,   // front top left 0
        -0.5f, -0.5f, 0.5f,   // front bottom left 1
        0.5f, -0.5f, 0.5f,   // front bottom right 2
        0.5f, 0.5f, 0.5f,  // front top right 3
        -0.5f, 0.5f, -0.5f,   // back top left 4
        0.5f, 0.5f, -0.5f,   // back top right 5
        -0.5f, -0.5f, -0.5f,   // back bottom left 6
        0.5f, -0.5f, -0.5f,  // back bottom right 7
        };

// Set color with red, green, blue and alpha (opacity) values
float color[] = { 0.63671875f, 0.76953125f, 0.22265625f, 1.0f };
float red[] = { 1.0f, 0.0f, 0.0f, 1.0f };
float blue[] = { 0.0f, 0.0f, 1.0f, 1.0f };
private short drawOrder[] = {
                                0, 1, 2, 0, 2, 3,//front
                                0, 4, 5, 0, 5, 3, //Top
                                0, 1, 6, 0, 6, 4, //left
                                3, 2, 7, 3, 7 ,5, //right
                                1, 2, 7, 1, 7, 6, //bottom
                                4, 6, 7, 4, 7, 5};//back (order to draw vertices)
final float[] cubeColor =
        {
                // Front face (red)
                       1.0f, 0.0f, 0.0f, 1.0f,
                        1.0f, 0.0f, 0.0f, 1.0f,
                        1.0f, 0.0f, 0.0f, 1.0f,
                        1.0f, 0.0f, 0.0f, 1.0f,
                        1.0f, 0.0f, 0.0f, 1.0f,
                        1.0f, 0.0f, 0.0f, 1.0f,
                // Top face (green)
                        0.0f, 1.0f, 0.0f, 1.0f,
                        0.0f, 1.0f, 0.0f, 1.0f,
                        0.0f, 1.0f, 0.0f, 1.0f,
                        0.0f, 1.0f, 0.0f, 1.0f,
                        0.0f, 1.0f, 0.0f, 1.0f,
                        0.0f, 1.0f, 0.0f, 1.0f,
                // Left face (blue)
                       0.0f, 0.0f, 1.0f, 1.0f,
                        0.0f, 0.0f, 1.0f, 1.0f,
                        0.0f, 0.0f, 1.0f, 1.0f,
                        0.0f, 0.0f, 1.0f, 1.0f,
                        0.0f, 0.0f, 1.0f, 1.0f,
                        0.0f, 0.0f, 1.0f, 1.0f,
                // Right face (yellow)
                       1.0f, 1.0f, 0.0f, 1.0f,
                        1.0f, 1.0f, 0.0f, 1.0f,
                        1.0f, 1.0f, 0.0f, 1.0f,
                        1.0f, 1.0f, 0.0f, 1.0f,
                        1.0f, 1.0f, 0.0f, 1.0f,
                        1.0f, 1.0f, 0.0f, 1.0f,
                // Bottom face (cyan)
                       0.0f, 1.0f, 1.0f, 1.0f,
                        0.0f, 1.0f, 1.0f, 1.0f,
                        0.0f, 1.0f, 1.0f, 1.0f,
                        0.0f, 1.0f, 1.0f, 1.0f,
                        0.0f, 1.0f, 1.0f, 1.0f,
                        0.0f, 1.0f, 1.0f, 1.0f,
                // Back face (magenta)
                       1.0f, 0.0f, 1.0f, 1.0f,
                        1.0f, 0.0f, 1.0f, 1.0f,
                        1.0f, 0.0f, 1.0f, 1.0f,
                        1.0f, 0.0f, 1.0f, 1.0f,
                        1.0f, 0.0f, 1.0f, 1.0f,
                        1.0f, 0.0f, 1.0f, 1.0f
        };

public MyCube() {
    // initialize vertex byte buffer for shape coordinates
    ByteBuffer bb = ByteBuffer.allocateDirect(
            // (# of coordinate values * 4 bytes per float)
            cubeCoords.length * 4);
    bb.order(ByteOrder.nativeOrder());
    vertexBuffer = bb.asFloatBuffer();
    vertexBuffer.put(cubeCoords);
    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);
    // initialize byte buffer for the color list
    ByteBuffer cb = ByteBuffer.allocateDirect(
            // (# of coordinate values * 2 bytes per short)
            cubeColor.length * 4);
    cb.order(ByteOrder.nativeOrder());
    colorBuffer = cb.asFloatBuffer();
    colorBuffer.put(cubeColor);
    colorBuffer.position(0);

    int vertexShader = MyRenderer.loadShader(GLES20.GL_VERTEX_SHADER,
            vertexShaderCode);
    int fragmentShader = MyRenderer.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 = cubeCoords.length / COORDS_PER_VERTEX;
private final int vertexStride = COORDS_PER_VERTEX * 4; // 4 bytes per vertex
public void draw(float[] mvpMatrix) { // pass in the calculated transformation matrix
    // Add program to OpenGL ES environment
    GLES20.glUseProgram(mProgram);
    // get handle to vertex shader's vPosition member
    mPositionHandle = GLES20.glGetAttribLocation(mProgram, "vPosition");
    // get handle to fragment shader's vColor member
    mColorHandle = GLES20.glGetUniformLocation(mProgram, "vColor");

    // Enable a handle to the cube vertices
    GLES20.glEnableVertexAttribArray(mPositionHandle);
    // Prepare the cube coordinate data
    GLES20.glVertexAttribPointer(mPositionHandle, COORDS_PER_VERTEX,
            GLES20.GL_FLOAT, false,
            vertexStride, vertexBuffer);

    // Set color for drawing the triangle
    //mColorHandle = GLES20.glGetUniformLocation(mProgram, "vColor");
    // Enable a handle to the cube colors
    GLES20.glEnableVertexAttribArray(mColorHandle);
    // Prepare the cube color data
    GLES20.glVertexAttribPointer(mColorHandle, 4, GLES20.GL_FLOAT, false, 16, colorBuffer);
    // Set the color for each of the faces
    //GLES20.glUniform4fv(mColorHandle, 1, blue, 0);
    //***When I add this line of code above, it can show a cube totally in blue.***
    // get handle to shape's transformation matrix
    mMVPMatrixHandle = GLES20.glGetUniformLocation(mProgram, "uMVPMatrix");
    // Pass the projection and view transformation to the shader
    GLES20.glUniformMatrix4fv(mMVPMatrixHandle, 1, false, mvpMatrix, 0);

    // Draw the cube
    GLES20.glDrawElements(GLES20.GL_TRIANGLES, drawOrder.length, GLES20.GL_UNSIGNED_SHORT, drawListBuffer);

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

}

Answer 1

从片段着色器中删除统一变量 vColor 声明。在顶点着色器中定义新的每个顶点属性输入变量，将该值写入顶点着色器输出的可变变量，并添加为由片段着色器读取的可变输入。