So, I created a scope in OpenGL ES (specifically, OpenGL ES 2.0, in Java, for Android). When this sphere is placed in the same place as the center used for my matrix of representations, this is good, but when the center is very poor, it is focused (see below).
Why is this happening and how to stop it?
This is the same area. The one in the upper right corner simply translates to x and y (not z).
Some code snippets from my implementation of GLSurfaceView.renderer,
public void onSurfaceCreated(GL10 unused, EGLConfig config) { GLES20.glClearColor(0.0f, 0.0f, 0.0f, 1.0f); GLES20.glEnable(GLES20.GL_CULL_FACE); GLES20.glEnable(GLES20.GL_DEPTH_TEST); // Both centred on (0,0,0), of radius 1.0. outerSphere = new Sphere(); centreSphere = new Sphere(); } public void onSurfaceChanged(GL10 unused, int width, int height) { GLES20.glViewport(0, 0, width, height); ratio = (float) width / height; final float left = -ratio; final float right = ratio; final float bottom = -1.0f; final float top = 1.0f; final float near = 1.0f; final float far = 100.0f; Matrix.frustumM(projMatrix, 0, left, right, bottom, top, near, far); } public void onDrawFrame(GL10 unused) { GLES20.glClear(GLES20.GL_DEPTH_BUFFER_BIT | GLES20.GL_COLOR_BUFFER_BIT); float eyeX = 0.0f; float eyeY = 0.0f; float eyeZ = 10.0f; final float lookX = 0.0f; final float lookY = 0.0f; final float lookZ = 0.0f; final float upX = 0.0f; final float upY = 1.0f; final float upZ = 0.0f; Matrix.setLookAtM(viewMatrix, 0, eyeX, eyeY, eyeZ, lookX, lookY, lookZ, upX, upY, upZ); // Set identity matrix as input for translations. Matrix.setIdentityM(outerModelMatrix, 0); // Translate outer sphere by 5 in x and y. Matrix.translateM(outerModelMatrix, 0, 5.0f, 5.0f, 0.0f); // MVP matrix = Projection * View * Model. Matrix.multiplyMM(centreMVPMatrix, 0, viewMatrix, 0, centreModelMatrix, 0); Matrix.multiplyMM(centreMVPMatrix, 0, projectionMatrix, 0, centreMVPMatrix, 0); Matrix.multiplyMM(outerMVPMatrix, 0, viewMatrix, 0, outerModelMatrix, 0); Matrix.multiplyMM(outerMVPMatrix, 0, projectionMatrix, 0, outerMVPMatrix, 0); outerSphere.draw(outerMVPMatrix); centreSphere.draw(outerMVPMatrix); }
And my shaders are just
private final static String vertexShaderCode = "uniform mat4 u_MVPMatrix;" + "attribute vec4 a_Position;" + "uniform vec4 u_Color;" + "void main() {" + " gl_Position = u_MVPMatrix * a_Position;" + "}"; private final static String fragmentShaderCode = "precision mediump float;" + "uniform vec4 u_Color;" + "void main() {" + " gl_FragColor = u_Color;" + "}";
I left almost all the code from the Sphere class, and other things that I do not think are necessary (?), But if they are needed, I will lay them out.