public void glPaint() {
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
glEnable(GL_LIGHTING);
glEnable(GL_LIGHT0);
glEnable(GL_DEPTH_TEST);
glEnableClientState(GL_NORMAL_ARRAY);
glEnableClientState(GL_VERTEX_ARRAY);
glVertexPointer(3, GL_FLOAT, 0, _buffer);
glNormalPointer(GL_FLOAT, 0, _buffer);
glColor3f(1.0f, 1.0f, 1.0f);
glDrawArrays(GL_TRIANGLES, 0, _buffer.capacity() / 3);
glFlush();
}
/**
* Computes the vertices of the triangles for rendering a sphere and stores them in _buffer.
* The vertices are repeated as necessary so that the buffer can be used by rendering with
* glDrawArrays.
*/
private void computeVertices() {
final int nphi = 50;
final int ntheta = 100;
final float dphi = (float) Math.PI / nphi;
final float dtheta = 2.0f * (float) Math.PI / ntheta;
float[] vertices = new float[2 * 3 * 3 * ntheta + (nphi - 2) * 3 * 6 * ntheta];
// Precompute trigonometry.
float[] phiSin = new float[nphi];
float[] phiCos = new float[nphi];
for (int i = 0; i < nphi; ++i) {
float phi = i * dphi;
phiSin[i] = (float) Math.sin(phi);
phiCos[i] = (float) Math.cos(phi);
}
float[] thetaSin = new float[ntheta];
float[] thetaCos = new float[ntheta];
for (int i = 0; i < ntheta; ++i) {
float theta = i * dtheta;
thetaSin[i] = (float) Math.sin(theta);
thetaCos[i] = (float) Math.cos(theta);
}
// Fan at north pole.
int index = 0;
for (int i = 0; i < ntheta; ++i) {
// Pole.
vertices[index++] = 0.0f; // x
vertices[index++] = 0.0f; // y
vertices[index++] = 1.0f; // z
vertices[index++] = thetaCos[i] * phiSin[1]; // x
vertices[index++] = thetaSin[i] * phiSin[1]; // y
vertices[index++] = phiCos[1]; // z
int j = (i + 1) % ntheta;
vertices[index++] = thetaCos[j] * phiSin[1];
vertices[index++] = thetaSin[j] * phiSin[1];
vertices[index++] = phiCos[1];
}
// Latitude strips.
for (int ip = 1; ip < nphi - 1; ++ip) {
for (int it = 0; it < ntheta; ++it) {
int jt = (it + 1) % ntheta;
vertices[index++] = thetaCos[it] * phiSin[ip];
vertices[index++] = thetaSin[it] * phiSin[ip];
vertices[index++] = phiCos[ip];
vertices[index++] = thetaCos[it] * phiSin[ip + 1];
vertices[index++] = thetaSin[it] * phiSin[ip + 1];
vertices[index++] = phiCos[ip + 1];
vertices[index++] = thetaCos[jt] * phiSin[ip];
vertices[index++] = thetaSin[jt] * phiSin[ip];
vertices[index++] = phiCos[ip];
vertices[index] = vertices[index - 3];
++index;
vertices[index] = vertices[index - 3];
++index;
vertices[index] = vertices[index - 3];
++index;
vertices[index] = vertices[index - 9];
++index;
vertices[index] = vertices[index - 9];
++index;
vertices[index] = vertices[index - 9];
++index;
vertices[index++] = thetaCos[jt] * phiSin[ip + 1];
vertices[index++] = thetaSin[jt] * phiSin[ip + 1];
vertices[index++] = phiCos[ip + 1];
}
}
// Fan at south pole.
for (int i = 0; i < ntheta; ++i) {
vertices[index++] = thetaCos[i] * phiSin[nphi - 1];
vertices[index++] = thetaSin[i] * phiSin[nphi - 1];
vertices[index++] = phiCos[nphi - 1];
// Pole.
vertices[index++] = 0.0f;
vertices[index++] = 0.0f;
vertices[index++] = 1.0f;
int j = (i + 1) % ntheta;
vertices[index++] = thetaCos[j] * phiSin[nphi - 1];
vertices[index++] = thetaSin[j] * phiSin[nphi - 1];
vertices[index++] = phiCos[nphi - 1];
}
_buffer =
ByteBuffer.allocateDirect(vertices.length * 4)
.order(ByteOrder.nativeOrder())
.asFloatBuffer();
_buffer.put(vertices);
_buffer.rewind();
}