Question:
I made a full-screen size square to show on window.But sadly, I am stuck at changing viewpoint (camera or perspective?) to make square look small at the center of window.
As many people suggested on web, I followed guid of setting up Matrix and perspective field of view which does not work…
I am wondering what I am missing on my code.
private void ImageControl_OnRender(TimeSpan delta)
{
//Create perspective camera matrix
//ImageControl is the name of window
GL.Viewport(0, 0, (int)ImageControl.Width, (int)ImageControl.Height);
GL.MatrixMode(MatrixMode.Projection);
GL.LoadIdentity();
Matrix4 perspectiveMatrix;
Matrix4.CreatePerspectiveFieldOfView(45.0f * (float)Math.PI / 180, (float)(ImageControl.Width / ImageControl.Height), 0.1f, 100.0f, out perspectiveMatrix);
//Set perspective camera
//GL.MatrixMode(MatrixMode.Projection);
//GL.LoadIdentity();
GL.LoadMatrix(ref perspectiveMatrix);
GL.LoadIdentity();
GL.MatrixMode(MatrixMode.Modelview);
//GL.MatrixMode(MatrixMode.Projection);
GL.LoadIdentity();
//Now starting to draw objects
//Set the background colour
GL.ClearColor(Color4.SkyBlue);
//Clear the colour and depth buffer for next matrix.
GL.Clear(ClearBufferMask.ColorBufferBit | ClearBufferMask.DepthBufferBit);
//Set the scale of object first hand
//GL.Scale(0.5f, 0.5f, 0.5f);
//GL.Translate() <<< Set the translation of object first hand GL.Translate(0.0f, 0.0f, -2.0f); //Set the colour of object first hand GL.Color3(0.3f, 0.2f, 0.5f); //Tells that we are going to draw a sqare consisting of vertices. Can be Triangle too! GL.Begin(PrimitiveType.Quads); GL.Vertex3(-1.0f, -1.0f, 0.0f); GL.Vertex3(1.0f, -1.0f, 0.0f); GL.Vertex3(1.0f, 1.0f, 0.0f); GL.Vertex3(-1.0f, 1.0f, 0.0f); //GL.TexParameter(TextureTarget.Texture2D, TextureParameterName.TextureWrapS, (int)TextureWrapMode.Repeat); //GL.TexParameter(TextureTarget.Texture2D, TextureParameterName.TextureWrapT, (int)TextureWrapMode.Repeat); //GL.TexParameter(TextureTarget.Texture2D, TextureParameterName.TextureMinFilter, (int)TextureMinFilter.Nearest); GL.End(); GL.Finish(); } [/code]
Answer:
You load the identity matrix after the projection matrix. This overrides the projection matrix. Do the following:// 1. Select projection matrix mode
GL.MatrixMode(MatrixMode.Projection); // <--- INSERT
// 2. Load projection matrix
GL.LoadMatrix(ref perspectiveMatrix);
// GL.LoadIdentity(); <--- DELETE
// 3. Select model view matrix mode
GL.MatrixMode(MatrixMode.Modelview);
// 4. Clear model view matrix (load the identity matrix)
GL.LoadIdentity();
// 5. Multiply model view matrix with the translation matrix
GL.Translate(0.0f, 0.0f, -2.0f);
[/code]
GL.MatrixMode selects the current matrix. All pending matrix operations affect the selected matrix. GL.LoadIdentity “clears” the matrix. It loads the Identity matrix.If you have better answer, please add a comment about this, thank you!