GLES20纹理在某些设备上不起作用 [英] GLES20 Texture Not Working on Some Devices

问题描述

我尝试在 Android的示例OpenGL 2.0的顶部添加一个相当简单的扩展项目，以便为基本形状添加纹理.这似乎很简单，但在某些设备(三星Nexus S，LG Optimus 3D和三星银河S)上，纹理无法渲染.

I have tried to add a fairly simple extension on top of Android's example OpenGL 2.0 project in order to add texturing to basic shapes. This seems pretty straightforward, but on certain devices (Samsung Nexus S, LG Optimus 3D, Samsung Galaxy S) the texture just does not render.

这实际上是我在一个更大的项目中遇到的一个问题，但是我能够在下面的简单项目中重现该问题，希望这里的人对我的代码在哪里出现问题有所了解，或如何为这些设备专门设计GL纹理(可能是设备存在问题).

要了解如何使用此对象:在GLSurfaceView.Renderer的onSurfaceCreated方法中，我实例化了Square()对象，在onDrawFrame方法中，我调用了Square的draw()方法.但是，所有与纹理相关的代码都应出现在此Square类中，这与Google自己的示例几乎完全相同.

To give an idea of how this object is used: In the GLSurfaceView.Renderer's onSurfaceCreated method I am instantiating a Square() object and in the onDrawFrame method I am calling Square's draw() method. However, all of the relevant code to dealing with textures should appear in this Square class which is almost exactly identical to Google's own example.

在此先感谢所有接受此操作的人.

Many thanks in advance to anyone who takes a crack at this.

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);
}
}

推荐答案

我猜这是一个二次幂问题.

I'll guess that this is a Power-of-two problem.

默认情况下，glTexParameter的GL_TEXTURE_WRAP设置被设置为GL_REPEAT，并且使用GL_REPEAT 必须的纹理必须具有二次幂的大小:

By default, the GL_TEXTURE_WRAP setting of glTexParameter is set to GL_REPEAT, and textures that use GL_REPEAT must be power-of-two sized:

同样，如果纹理图像的宽度或高度不是2的幂，并且 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 ，则纹理图像单元将返回 (R，G，B，A)=(0，0，0，1).

Similarly, if the width or height of a texture image are not powers of two and either the GL_TEXTURE_MIN_FILTER is set to one of the functions that requires mipmaps or the GL_TEXTURE_WRAP_S or GL_TEXTURE_WRAP_T is not set to GL_CLAMP_TO_EDGE, then the texture image unit will return (R, G, B, A) = (0, 0, 0, 1).

您可以从2的幂开始，但是当您使用BitmapFactory.decodeResource生成位图时，它会根据设备的密度来缩放比例(?).因此，例如，如果您从HDPI设备上的drawable文件夹中加载512 * 512的源纹理，我相信它会将其缩放1.5倍，那么您剩下的不是Po2.

You may start with a power-of-two texture, but when you use a BitmapFactory.decodeResource to generate a bitmap, it helpfully(?) scales this based on the density of a device. So for example if you load a 512*512 source texture from drawable folder on a HDPI device, I believe it scales it by 1.5x, so you're left with something that is not Po2.

这给您的结果是纹理无法在大量设备上运行，因为这些设备的密度都很高，导致您生成非法的纹理尺寸.

This gives you the result that your textures don't work on a ton of devices, because those devices are all of a density that causes you to generate illegal texture sizes.

在这种情况下，解决方案是将(2的幂)个源纹理放入资源文件夹drawable-nodpi中，这将防止任何基于密度的缩放.要么使用CLAMP_TO_EDGE，要么不关心Po2.

The solution in this case would be to place your (power of 2) source texture into the resource folder drawable-nodpi, which will prevent any density-based scaling. Either that or use CLAMP_TO_EDGE, which doesn't care about Po2.

这篇关于GLES20纹理在某些设备上不起作用的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！