ABS newbie trying to get it to work
Posted Friday, 16 September, 2011 - 19:55 by Fidchells_eye inFidchells_eye here again
I am converting an old C++ to C#
But before i can continue to do that I need the test render function DrawX() to draw an X on screen
But my setup function is failing, due to GL being NULL.
The structure of the project is;
BaseScope is inherited into any ToolScope Class.
The BaseScope class is used in the ModularScopeDisplay class so I can switch the tools as needed
The main does have a GLControl called GLDisplay1.
public class ModularScopeDisplay
{
#region Data
ScopeBase sBase;
#endregion
public ModularScopeDisplay(OpenTK.GLControl GL_Display, ScopeBase.ScopeMode mode)
{
if (mode == ScopeBase.ScopeMode.WFM)
{
sBase = new Scope_WFM(ref GL_Display);
}
//gl = GL_Display;
}
}
public abstract class ScopeBase
{
...
protected OpenTK.Graphics.OpenGL.GL gl;
...
}
public class Scope_WFM:ScopeBase
{
.....
}
Comments
Re: ABS newbie trying to get it to work
OpenTK.Graphics.OpenGL.GL is a static class. You do not create references to it, you just call GL.SomeFunction() directly.
Re: ABS newbie trying to get it to work
I get an error where GL static class is NULL
Re: ABS newbie trying to get it to work
This is wrong:
This is correct:
Re: ABS newbie trying to get it to work
the error is
"NULLreference exception was unhandled"
code
public virtual bool SetupProjection(int width, int height) //configures OpenGL camera properties
{
if (height == 0) // don't want a divide by zero
{
height = 1;
}
m_Zdelta = (float)((height/2)/(Math.Tan(FovY/2)));
// \/ zoom factor
//m_Zdelta = m_Zdelta * 2.45;
GL.Viewport(0, 0, width, height); // reset the viewport to new dimensions <------------------------Getting exception here
GL.MatrixMode(MatrixMode.Projection); // set projection matrix current matrix
GL.LoadIdentity(); // reset projection matrix
// calculate aspect ratio of window
Matrix4.CreatePerspectiveFieldOfView(FovY,(float)width/(float)height,200.0f,2000.0f);
GL.MatrixMode(MatrixMode.Modelview); // set modelview matrix
GL.LoadIdentity(); // reset modelview matrix
//load window dimensions into class memory
m_windowWidth = (float)width;
m_windowHeight = (float)height;
return true;
}
Re: ABS newbie trying to get it to work
The code you are showing seems ok. Probably the error is somewhere else.
If you try to call a GL function before you have initialized the opengl context you get that kind of exception. Check if you are calling that function inside a window resize event since, if I correctly remember, the resize event is called even before the window loaded event, the place where I usually initialize the opengl context.
What I usually do is create a bool variable to check if the context is initialized to avoid calling GL functions in this kind of situations.
Re: ABS newbie trying to get it to work
Then how do you initialize the opengl context?
this code is not being executed in a resize event it is executed in the main form's constructor.
GLDisplay1 is a GLControl on the main form.
code
Scope_WFM scope;
public frmMain()
{
InitializeComponent();
scope = new Scope_WFM(ref this.GLDisplay1);
scope.SetupProjection(GLDisplay1.Size.Width, GLDisplay1.Size.Height);
scope.DrawX();
}
Re: ABS newbie trying to get it to work
The GLControl initializes the opengl context for you.
Make sure that your GLControl is properly initialized before calling any GL function. Move the code:
to your GLControl paint event. It does not look good to call draw calls inside the constructor everything that is needed might not be ready.
I am not sure and I might be wrong but the problem might be that there is no gl context active at that moment.
Re: ABS newbie trying to get it to work
GLDisplay1.Size.Width, GLDisplay1.Size.Height give data (320 and 240)
I moved the
scope.SetupProjection(GLDisplay1.Size.Width, GLDisplay1.Size.Height);
scope.DrawX();
to a button and it got past the viewport thanks.
but it now stops at
Matrix4.CreatePerspectiveFieldOfView(FovY,(float)width/(float)height,200.0f,2000.0f); <-------------FovY = 52.0
error: argument out of range exception
Re: ABS newbie trying to get it to work
that function requires that the field of view in radians not in degrees (52 is a big number in radians) and is limited between 0 and PI.
Part of the internal code for Matrix4.CreatePerspectiveFieldOfView says:
Re: ABS newbie trying to get it to work
Thanks, that got it.
but it is not rendering, I get a white GL control.
Does the GL or GL control need an init to be called?
public override void DrawX() // a display test function
{
//setup GL_RENDERING
GL.Clear(ClearBufferMask.ColorBufferBit | ClearBufferMask.DepthBufferBit); // clear screen and depth buffer
GL.LoadIdentity(); //load matrix identity // \/ zoom factor
Matrix4.LookAt((m_windowWidth / 2), (m_windowHeight / 2), (m_Zdelta * (2.70f + 0.00f)), //camera
(m_windowWidth / 2), (m_windowHeight / 2), (float)0.0, //view center
(float)0.0, (float)1.0, (float)0.0); //camera orientation
/*gluLookAt((m_windowWidth/2), (m_windowHeight/2), (m_Zdelta* (2.70f + 0.00f)), //camera
(m_windowWidth/2), (m_windowHeight/2), 0.0, //view center
0.0, 1.0, 0.0); //camera orientation*/
GL.Begin(BeginMode.Lines);
GL.Vertex3(0.0f, 0.0f, 0.0f);
GL.Vertex3((float)m_windowWidth, (float)m_windowHeight, 0.0f);
GL.Vertex3(0.0f, (float)m_windowHeight, 0.0f);
GL.Vertex3((float)m_windowWidth, 0.0f, 0.0f);
GL.End();
}