GLES20紋理在某些設備上不起作用

Question

我試圖在Android示例OpenGL 2.0項目的頂部添加一個相當簡單的擴展，以便將紋理添加到基本形狀中。 這似乎很簡單，但是在某些設備（三星Nexus S，LG Optimus 3D和三星Galaxy S）上，紋理無法渲染。

這實際上是我在一個更大的項目上遇到的一個問題，但是我能夠通過下面的簡單項目重現該問題，希望這里的人對我的代碼在哪里提出問題有所了解，或者如何專門設計GL這些設備的紋理（設備可能存在問題）。

給出如何使用該對象的想法：在GLSurfaceView.Renderer的onSurfaceCreated方法中，我實例化了Square()對象，在onDrawFrame方法中，我調用了Square的draw()方法。 但是，所有與紋理相關的代碼都應出現在此Square類中，這幾乎與Google自己的示例完全相同。

在此先感謝任何對此有所幫助的人。

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;" +
    "attribute vec2 a_TexCoordinate;" +

    "varying vec2 v_TexCoordinate;" +

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

private final String fragmentShaderCode =
    "precision mediump float;" +

    "uniform sampler2D u_Texture;" +

    "varying vec2 v_TexCoordinate;" +

    "void main() {" +
    "  gl_FragColor = texture2D(u_Texture, v_TexCoordinate);" +
    "}";

private final FloatBuffer vertexBuffer;
private final FloatBuffer textureBuffer;
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

final float[] previewTextureCoordinateData =
    {
        0.0f, 1.0f,
        0.0f, 0.0f, 
        1.0f, 1.0f,
        1.0f, 0.0f
    };

private int textureDataHandle;
private int textureUniformHandle;
private int textureCoordinateHandle;

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 };

private int loadTexture(final Context context, final int resourceId)
{
    final int[] textureHandle = new int[1];

    GLES20.glGenTextures(1, textureHandle, 0);

    if (textureHandle[0] != 0)
    {
        final BitmapFactory.Options options = new BitmapFactory.Options();
        options.inScaled = false;   // No pre-scaling

        // Read in the resource
        final Bitmap bitmap = BitmapFactory.decodeResource(context.getResources(), resourceId, options);

        // Bind to the texture in OpenGL
        GLES20.glBindTexture(GLES20.GL_TEXTURE_2D, textureHandle[0]);

        // Set filtering
        GLES20.glTexParameteri(GLES20.GL_TEXTURE_2D, GLES20.GL_TEXTURE_MIN_FILTER, GLES20.GL_NEAREST);
        GLES20.glTexParameteri(GLES20.GL_TEXTURE_2D, GLES20.GL_TEXTURE_MAG_FILTER, GLES20.GL_NEAREST);

        // Load the bitmap into the bound texture.
        GLUtils.texImage2D(GLES20.GL_TEXTURE_2D, 0, bitmap, 0);

        // Recycle the bitmap, since its data has been loaded into OpenGL.
        bitmap.recycle();
    }

    if (textureHandle[0] == 0)
    {
        throw new RuntimeException("Error loading texture.");
    }

    return textureHandle[0];
}

public Square(Context context) {
    // 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);


    ByteBuffer texCoordinates = ByteBuffer.allocateDirect(previewTextureCoordinateData.length * 4);
    texCoordinates.order(ByteOrder.nativeOrder());
    textureBuffer = texCoordinates.asFloatBuffer();
    textureBuffer.put(previewTextureCoordinateData);
    textureBuffer.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);

    textureDataHandle = loadTexture(context, R.drawable.color_texture);

    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);

    textureCoordinateHandle = GLES20.glGetAttribLocation(mProgram, "a_TexCoordinate");
    GLES20.glVertexAttribPointer(textureCoordinateHandle, 2, GLES20.GL_FLOAT, false, 
            0, textureBuffer);
    GLES20.glEnableVertexAttribArray(textureCoordinateHandle);

    textureUniformHandle = GLES20.glGetUniformLocation(mProgram, "u_Texture");
    MyGLRenderer.checkGlError("glGetUniformLocation");
    GLES20.glActiveTexture(GLES20.GL_TEXTURE0);
    GLES20.glBindTexture(GLES20.GL_TEXTURE_2D, textureDataHandle);
    GLES20.glUniform1i(textureUniformHandle, 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);
}
}

Answer 1

我猜這是一個二次冪問題。

默認情況下， GL_TEXTURE_WRAP的glTexParameter設置設置為GL_REPEAT ，並且使用GL_REPEAT紋理的GL_REPEAT 必須為2的冪次方：

同樣，如果紋理圖像的寬度或高度不是2的冪，並且GL_TEXTURE_MIN_FILTER設置為需要mipmap的函數之一， 或者GL_TEXTURE_WRAP_S或GL_TEXTURE_WRAP_T未設置為GL_CLAMP_TO_EDGE ，則紋理圖像單元將返回（R ，G，B，A）=（0，0，0，1）。

您可以從二次冪紋理開始，但是當您使用BitmapFactory.decodeResource生成位圖時，它會根據設備的密度來縮放比例（？）。 因此，例如，如果您從HDPI設備上的drawable文件夾中加載512 * 512源紋理，我相信它會將其縮放1.5倍，因此剩下的不是Po2。

這給您的結果是紋理無法在大量設備上運行，因為這些設備的密度都很高，導致您生成非法的紋理尺寸。

在這種情況下，解決方案是將（2的冪）源紋理放入資源文件夾drawable-nodpi ，這將防止任何基於密度的縮放。 要么使用CLAMP_TO_EDGE，要么不關心Po2。