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POCorrect vertex shader code? OpenGL ES 2.0
 

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  1. POCorrect vertex shader code? OpenGL ES 2.0
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    <p><strong>Edit</strong> Code added, please see below</p> <p><strong>Edit 2</strong> - Screenshots from device included at bottom along with explanation</p> <p><strong>Edit 3</strong> - New code added</p> <p>I have 2 classes, a rendered and a custom 'quad' class.</p> <p>I have these declared at class level in my renderer class:</p> <pre><code>final float[] mMVPMatrix = new float[16]; final float[] mProjMatrix = new float[16]; final float[] mVMatrix = new float[16]; </code></pre> <p>And in my onSurfaceChanged method I have:</p> <p>@Override public void onSurfaceChanged(GL10 gl, int width, int height) {</p> <pre><code> GLES20.glViewport(0, 0, width, height); float ratio = (float) width / height; Matrix.frustumM(mProjMatrix, 0, -ratio, ratio, -1, 1, 3, 7); } </code></pre> <p>and....</p> <pre><code> 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); } </code></pre> <p>And finally from this class, onDrawFrame:</p> <pre><code>@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 } </code></pre> <p>Then, in my quad class:</p> <p>This declared at class level:</p> <pre><code> 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);" + "}"; </code></pre> <p>Then method for setting texture (don't think this is relevant to this problem though!!)</p> <pre><code> 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); } </code></pre> <p>And finally, my 'rotateQuad' method (which currently is supposed to draw and rotate the quad).</p> <pre><code>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); } </code></pre> <p>for Edit 2.</p> <p>This is my quad as drawn in the center of the screen. No rotation.</p> <p><img src="https://i.stack.imgur.com/dMKbH.png" alt="enter image description here"></p> <p>This is the same quad rotated at +45 Degrees with the code "gl_Position = a_position * uMVPMatrix;" + in my vertex shader (it's from a different project now so the shader variable is a_position and not vPosition), it's looks correct!</p> <p><img src="https://i.stack.imgur.com/LJXL0.png" alt="enter image description here"></p> <p>However, this is the same quad rotated at +45 Degrees with the 2 shader variables switched (so they read "gl_Position = uMVPMatrix * a_position;" - as you can see, it's not quite right.</p> <p>Also just a side note, you can't see it here as the quare is symetrical, but each method also rotates in the opposite direction to the other....</p> <p><img src="https://i.stack.imgur.com/p94Jv.png" alt="enter image description here"></p> <p>Any help appreciated.</p>
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