Edit Added code, see below
Change 2 . Screenshots from the device below, along with an explanation
Edit 3 - added new code
I have 2 classes, rendering and custom class "quad".
I declared this at the class level in the renderer class:
final float[] mMVPMatrix = new float[16];
final float[] mProjMatrix = new float[16];
final float[] mVMatrix = new float[16];
And in my onSurfaceChanged method, I have:
@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);
}
and....
public void onSurfaceCreated(GL10 gl, EGLConfig config) {
myBitmap = BitmapFactory.decodeResource(curView.getResources(), R.drawable.box);
dot1 = new Quad();
dot1.setTexture(curView, myBitmap);
dot1.setSize(300,187);
myBitmap.recycle();
GLES20.glClearColor(0, 0, 0, 1);
}
And finally, from this class, onDrawFrame:
@Override
public void onDrawFrame(GL10 gl) {
GLES20.glClear(GLES20.GL_COLOR_BUFFER_BIT);
Matrix.setLookAtM(mVMatrix, 0, 0, 0, 3, 0f, 0f, 0f, 0f, 1.0f, 0.0f);
Matrix.multiplyMM(mMVPMatrix, 0, mProjMatrix, 0, mVMatrix, 0);
dot1.rotateQuad(0,0,45, mMVPMatrix);
}
Then in my quad class:
This is declared at the class level:
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;
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 * uMVPMatrix;\n"+
"v_texCoords = a_texCoords;" +
"}";
String strFShader =
"precision mediump float;" +
"varying vec2 v_texCoords;" +
"uniform sampler2D u_baseMap;" +
"void main()" +
"{" +
"gl_FragColor = texture2D(u_baseMap, v_texCoords);" +
"}";
Then a texture adjustment method (don't think this applies to this problem!)
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);
}
And finally, my rotateQuad method (which currently needs to draw and rotate the quad).
public void rotateQuad(float x, float y, int angle, float[] mvpMatrix){
Matrix.setRotateM(mRotationMatrix, 0, angle, 0, 0, 0.1f);
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);
GLES20.glBindTexture(GLES20.GL_TEXTURE_2D, texID);
GLES20.glUseProgram(iProgId);
mMVPMatrixHandle = GLES20.glGetUniformLocation(iProgId, "uMVPMatrix");
GLES20.glUniformMatrix4fv(mMVPMatrixHandle, 1, false, mvpMatrix, 0);
mRotationHandle = GLES20.glGetUniformLocation(iProgId, "uRotate");
GLES20.glUniformMatrix4fv(mRotationHandle, 1, false, mRotationMatrix, 0);
vertexBuf.position(0);
GLES20.glVertexAttribPointer(iPosition, 3, GLES20.GL_FLOAT, false, 5 * 4, vertexBuf);
GLES20.glEnableVertexAttribArray(iPosition);
vertexBuf.position(3);
GLES20.glVertexAttribPointer(iTexCoords, 2, GLES20.GL_FLOAT, false, 5 * 4, vertexBuf);
GLES20.glEnableVertexAttribArray(iTexCoords);
GLES20.glDrawArrays(GLES20.GL_TRIANGLE_STRIP, 0, 4);
}
for Edit 2.
, . .

, +45 "gl_Position = a_position * uMVPMatrix;" + ( , - a_position, vPosition), !

, , +45 , ( "gl_Position = uMVPMatrix * a_position;" - , .
, , , ....

.