添加了编辑代码，请参见下文
编辑 2 - 底部包含设备的屏幕截图以及说明
编辑 3 - 添加了新代码
我有 2 个类，一个渲染的和一个自定义的“quad”类。
我在渲染器类的类级别声明了这些：
final float[] mMVPMatrix = new float[16];
final float[] mProjMatrix = new float[16];
final float[] mVMatrix = new float[16];
在我的 onSurfaceChanged 方法中，我有：
@Override public void onSurfaceChanged(GL10 gl, int width, int height) {
GLES20.glViewport(0, 0, width, height);
float ratio = (float) width / height;
Matrix.frustumM(mProjMatrix, 0, -ratio, ratio, -1, 1, 3, 7);
}
和....
public void onSurfaceCreated(GL10 gl, EGLConfig config) {
// TODO Auto-generated method stub
myBitmap = BitmapFactory.decodeResource(curView.getResources(), R.drawable.box);
//Create new Dot objects
dot1 = new Quad();
dot1.setTexture(curView, myBitmap);
dot1.setSize(300,187); //These numbers are the size but are redundant/not used at the moment.
myBitmap.recycle();
//Set colour to black
GLES20.glClearColor(0, 0, 0, 1);
}
最后来自这个类，onDrawFrame：
@Override
public void onDrawFrame(GL10 gl) {
// TODO Auto-generated method stub
//Paint the screen the colour defined in onSurfaceCreated
GLES20.glClear(GLES20.GL_COLOR_BUFFER_BIT);
// Set the camera position (View matrix) so looking from the front
Matrix.setLookAtM(mVMatrix, 0, 0, 0, 3, 0f, 0f, 0f, 0f, 1.0f, 0.0f);
// Combine
Matrix.multiplyMM(mMVPMatrix, 0, mProjMatrix, 0, mVMatrix, 0);
dot1.rotateQuad(0,0,45, mMVPMatrix); //x,y,angle and matrix passed in
}
然后，在我的四人班：
这在类级别声明：
private float[] mRotationMatrix = new float[16];
private final float[] mMVPMatrix = new float[16];
private final float[] mProjMatrix = new float[16];
private final float[] mVMatrix = new float[16];
private int mMVPMatrixHandle;
private int mPositionHandle;
private int mRotationHandle;
//Create our vertex shader
String strVShader =
"uniform mat4 uMVPMatrix;" +
"uniform mat4 uRotate;" +
"attribute vec4 a_position;\n"+
"attribute vec2 a_texCoords;" +
"varying vec2 v_texCoords;" +
"void main()\n" +
"{\n" +
// "gl_Position = a_position * uRotate;\n"+
// "gl_Position = uRotate * a_position;\n"+
"gl_Position = a_position * uMVPMatrix;\n"+
// "gl_Position = uMVPMatrix * a_position;\n"+
"v_texCoords = a_texCoords;" +
"}";
//Fragment shader
String strFShader =
"precision mediump float;" +
"varying vec2 v_texCoords;" +
"uniform sampler2D u_baseMap;" +
"void main()" +
"{" +
"gl_FragColor = texture2D(u_baseMap, v_texCoords);" +
"}";
然后设置纹理的方法（但不要认为这与这个问题有关！！）
public void setTexture(GLSurfaceView view, Bitmap imgTexture){
this.imgTexture=imgTexture;
iProgId = Utils.LoadProgram(strVShader, strFShader);
iBaseMap = GLES20.glGetUniformLocation(iProgId, "u_baseMap");
iPosition = GLES20.glGetAttribLocation(iProgId, "a_position");
iTexCoords = GLES20.glGetAttribLocation(iProgId, "a_texCoords");
texID = Utils.LoadTexture(view, imgTexture);
}
最后，我的“rotateQuad”方法（目前应该绘制和旋转四边形）。
public void rotateQuad(float x, float y, int angle, float[] mvpMatrix){
Matrix.setRotateM(mRotationMatrix, 0, angle, 0, 0, 0.1f);
// Matrix.translateM(mRotationMatrix, 0, 0, 0, 0); //Removed temporarily
// Combine the rotation matrix with the projection and camera view
Matrix.multiplyMM(mvpMatrix, 0, mRotationMatrix, 0, mvpMatrix, 0);
float[] vertices = {
-.5f,.5f,0, 0,0,
.5f,.5f,0, 1,0,
-.5f,-.5f,0, 0,1,
.5f,-.5f,0, 1,1
};
vertexBuf = ByteBuffer.allocateDirect(vertices.length * 4).order(ByteOrder.nativeOrder()).asFloatBuffer();
vertexBuf.put(vertices).position(0);
//Bind the correct texture
GLES20.glBindTexture(GLES20.GL_TEXTURE_2D, texID);
//Use program
GLES20.glUseProgram(iProgId);
// get handle to shape's transformation matrix
mMVPMatrixHandle = GLES20.glGetUniformLocation(iProgId, "uMVPMatrix");
// Apply the projection and view transformation
GLES20.glUniformMatrix4fv(mMVPMatrixHandle, 1, false, mvpMatrix, 0);
// get handle to shape's rotation matrix
mRotationHandle = GLES20.glGetUniformLocation(iProgId, "uRotate");
// Apply the projection and view transformation
GLES20.glUniformMatrix4fv(mRotationHandle, 1, false, mRotationMatrix, 0);
//Set starting position for vertices
vertexBuf.position(0);
//Specify attributes for vertex
GLES20.glVertexAttribPointer(iPosition, 3, GLES20.GL_FLOAT, false, 5 * 4, vertexBuf);
//Enable attribute for position
GLES20.glEnableVertexAttribArray(iPosition);
//Set starting position for texture
vertexBuf.position(3);
//Specify attributes for vertex
GLES20.glVertexAttribPointer(iTexCoords, 2, GLES20.GL_FLOAT, false, 5 * 4, vertexBuf);
//Enable attribute for texture
GLES20.glEnableVertexAttribArray(iTexCoords);
//Draw it
GLES20.glDrawArrays(GLES20.GL_TRIANGLE_STRIP, 0, 4);
}
对于编辑 2。
这是我在屏幕中央绘制的四边形。没有旋转。
这是以 +45 度旋转的同一个四边形，代码为“gl_Position = a_position * uMVPMatrix;” + 在我的顶点着色器中（它现在来自不同的项目，所以着色器变量是 a_position 而不是 vPosition），它看起来是正确的！
但是，这是在 2 个着色器变量切换的情况下以 +45 度旋转的同一个四边形（因此它们读取“gl_Position = uMVPMatrix * a_position;” - 如您所见，它不太正确。
也只是一个旁注，你在这里看不到它，因为四边形是对称的，但每种方法也会以与另一种相反的方向旋转......
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