How to translate along Z axis in OpenTK
- by JeremyJAlpha
I am playing around with an OpenGL sample application I downloaded for Xamarin-Android. The sample application produces a rotating colored cube I would simply like to edit it so that the rotating cube is translated along the Z axis and disappears into the distance.
I modified the code by:
adding an cumulative variable to store my Z distance,
adding GL.Enable(All.DepthBufferBit) - unsure if I put it in the right place,
adding GL.Translate(0.0f, 0.0f, Depth) - before the rotate functions,
Result: cube rotates a couple of times then disappears, it seems to be getting clipped out of the frustum.
So my question is what is the correct way to use and initialize the Z buffer and get the cube to travel along the Z axis? I am sure I am missing some function calls but am unsure of what they are and where to put them.
I apologise in advance as this is very basic stuff but am still learning :P, I would appreciate it if anyone could show me the best way to get the cube to still rotate but to also move along the Z axis. I have commented all my modifications in the code:
// This gets called when the drawing surface is ready
protected override void OnLoad (EventArgs e)
{
// this call is optional, and meant to raise delegates
// in case any are registered
base.OnLoad (e);
// UpdateFrame and RenderFrame are called
// by the render loop. This is takes effect
// when we use 'Run ()', like below
UpdateFrame += delegate (object sender, FrameEventArgs args) {
// Rotate at a constant speed
for (int i = 0; i < 3; i ++)
rot [i] += (float) (rateOfRotationPS [i] * args.Time);
};
RenderFrame += delegate {
RenderCube ();
};
GL.Enable(All.DepthBufferBit); //Added by Noob
GL.Enable(All.CullFace);
GL.ShadeModel(All.Smooth);
GL.Hint(All.PerspectiveCorrectionHint, All.Nicest);
// Run the render loop
Run (30);
}
void RenderCube ()
{
GL.Viewport(0, 0, viewportWidth, viewportHeight);
GL.MatrixMode (All.Projection);
GL.LoadIdentity ();
if ( viewportWidth > viewportHeight )
{
GL.Ortho(-1.5f, 1.5f, 1.0f, -1.0f, -1.0f, 1.0f);
}
else
{
GL.Ortho(-1.0f, 1.0f, -1.5f, 1.5f, -1.0f, 1.0f);
}
GL.MatrixMode (All.Modelview);
GL.LoadIdentity ();
Depth -= 0.02f; //Added by Noob
GL.Translate(0.0f,0.0f,Depth); //Added by Noob
GL.Rotate (rot[0], 1.0f, 0.0f, 0.0f);
GL.Rotate (rot[1], 0.0f, 1.0f, 0.0f);
GL.Rotate (rot[2], 0.0f, 1.0f, 0.0f);
GL.ClearColor (0, 0, 0, 1.0f);
GL.Clear (ClearBufferMask.ColorBufferBit);
GL.VertexPointer(3, All.Float, 0, cube);
GL.EnableClientState (All.VertexArray);
GL.ColorPointer (4, All.Float, 0, cubeColors);
GL.EnableClientState (All.ColorArray);
GL.DrawElements(All.Triangles, 36, All.UnsignedByte, triangles);
SwapBuffers ();
}
