Question

我尝试在Android's example OpenGL 2.0 project之上添加一个相当简单的扩展，以便为基本形状添加纹理。这个似乎非常简单，但在某些设备（三星Nexus S，LG Optimus 3D，三星Galaxy S）上，纹理无法呈现。

这实际上是我在一个更大的项目上遇到的问题，但我能够通过下面的简单项目重现这个问题，希望有人知道我的代码在哪里出现问题，或者如何为这些设备专门设计GL纹理（可能存在设备问题）。

要了解如何使用此对象：在GLSurfaceView.Renderer的onSurfaceCreated方法中，我实例化Square()对象，并在onDrawFrame方法中调用Square draw() 1}}方法。但是，处理纹理的所有相关代码都应出现在此Square类中，这几乎与Google自己的示例完全相同。

非常感谢任何对此有所了解的人。

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

我猜这是一个二人权问题。

默认情况下，GL_TEXTURE_WRAP的{{1}}设置设置为glTexParameter，使用GL_REPEAT 的纹理必须才能实现两个大小：

类似地，如果纹理图像的宽度或高度不是2和2的幂 GL_TEXTURE_MIN_FILTER设置为需要mipmap的功能之一 或GL_TEXTURE_WRAP_S或GL_TEXTURE_WRAP_T不是设置为GL_CLAMP_TO_EDGE ，然后纹理图像单元将返回（R，G，B，A）=（0,0,0,1）。

你可以从一个二次幂纹理开始，但是当你使用GL_REPEAT生成一个位图时，它会根据设备的密度来帮助（？）进行缩放。因此，例如，如果您在HDPI设备上从BitmapFactory.decodeResource文件夹加载512 * 512源纹理，我相信它会将其缩放1.5倍，因此您将留下不是Po2的东西。

这样可以得到纹理在大量设备上不起作用的结果，因为这些设备的密度都会导致您生成非法的纹理大小。

在这种情况下的解决方案是将您的（2的幂）源纹理放入资源文件夹drawable，这将阻止任何基于密度的缩放。或者使用CLAMP_TO_EDGE，它不关心Po2。

GLES20纹理在某些设备上不起作用

1 个答案: