我正在使用https://github.com/d3kod/Texample2中的代码在 OpenGL 2.0 中呈现文本。该项目的解释可以在http://primalpond.wordpress.com/2013/02/26/rendering-text-in-opengl-2-0-es-on-android/找到
该代码在我运行 android 4.1.2 的三星 Galaxy S3 上运行良好。但是，它在我运行 android 2.3.4 的 Droid X 上不起作用，并且其他人在 android 4.0.4 Onepad 940 平板电脑上遇到了这个问题（参见http://primalpond.wordpress.com/2013/02/26 /rendering-text-in-opengl-2-0-es-on-android/#comment-89）。
我在线路上收到 1281 错误：
GLES20.glEnableVertexAttribArray(mColorHandle)
我确定这是因为GL_MAX_VERTEX_ATTRIBS我的 Droid X 上的只有 8，并且mColorHandle设置为 26。当我在三星 GS3 上运行我的应用程序时，GL_MAX_VERTEX_ATTRIBS是 16，但mColorHandle设置为 0。
所以从 26>8 开始，就会抛出 1281 错误。我不明白为什么 Droid 的句柄值为 26，而 GS3 的句柄值为 0。
该mProgram程序在对象构造函数的这一行中设置：
mColorHandle = GLES20.glGetUniformLocation(mProgram.getHandle(), "u_Color");
这是产生错误的行：
void initDraw(float red, float green, float blue, float alpha) {
GLES20.glUseProgram(mProgram.getHandle()); // specify the program to use
// set color TODO: only alpha component works, text is always black #BUG
float[] color = {red, green, blue, alpha};
GLES20.glUniform4fv(mColorHandle, 1, color , 0);
GLES20.glEnableVertexAttribArray(mColorHandle);
GLES20.glActiveTexture(GLES20.GL_TEXTURE0); // Set the active texture unit to texture unit 0
GLES20.glBindTexture(GLES20.GL_TEXTURE_2D, textureId); // Bind the texture to this unit
// Tell the texture uniform sampler to use this texture in the shader by binding to texture unit 0
GLES20.glUniform1i(mTextureUniformHandle, 0);
//Log.i("error", "glerror3: " + GLES20.glGetError());
}
编辑
这是设置程序的类：
public class BatchTextProgram extends Program {
private static final AttribVariable[] programVariables = {
AttribVariable.A_Position, AttribVariable.A_TexCoordinate, AttribVariable.A_MVPMatrixIndex
};
private static final String vertexShaderCode =
"uniform mat4 u_MVPMatrix[24]; \n" // An array representing the combined
// model/view/projection matrices for each sprite
+ "attribute float a_MVPMatrixIndex; \n" // The index of the MVPMatrix of the particular sprite
+ "attribute vec4 a_Position; \n" // Per-vertex position information we will pass in.
+ "attribute vec2 a_TexCoordinate;\n" // Per-vertex texture coordinate information we will pass in
+ "varying vec2 v_TexCoordinate; \n" // This will be passed into the fragment shader.
+ "void main() \n" // The entry point for our vertex shader.
+ "{ \n"
+ " int mvpMatrixIndex = int(a_MVPMatrixIndex); \n"
+ " v_TexCoordinate = a_TexCoordinate; \n"
+ " gl_Position = u_MVPMatrix[mvpMatrixIndex] \n" // gl_Position is a special variable used to store the final position.
+ " * a_Position; \n" // Multiply the vertex by the matrix to get the final point in
// normalized screen coordinates.
+ "} \n";
private static final String fragmentShaderCode =
"uniform sampler2D u_Texture; \n" // The input texture.
+ "precision mediump float; \n" // Set the default precision to medium. We don't need as high of a
// precision in the fragment shader.
+ "uniform vec4 u_Color; \n"
+ "varying vec2 v_TexCoordinate; \n" // Interpolated texture coordinate per fragment.
+ "void main() \n" // The entry point for our fragment shader.
+ "{ \n"
+ " gl_FragColor = texture2D(u_Texture, v_TexCoordinate).w * u_Color;\n" // texture is grayscale so take only grayscale value from
// it when computing color output (otherwise font is always black)
+ "} \n";
@Override
public void init() {
super.init(vertexShaderCode, fragmentShaderCode, programVariables);
}
}