1. 1 Viewing & Projective Window Chapter 3

2. 2 D3D virtual viewpoint Definition: virtual viewpoint is like a camera that was positioned in some where and oriented in some direction. Then from this location and direction we can see that part of our world in the monitor. This viewable solid is called viewing frustum. Eventually, we will get a 2D image in the projection window for all objects.

3. 3 3 parameters to set viewpoint (i) Location of the Camera (ii) Looking direction (iii) Up direction. Up direction In real world, the default up direction is (0, 0, 1). However, in 3D program, the default up direction is (0, 1, 0), which is y-axis.

4. 4 Viewpoint Matrix Viewpoint matrix is Call the following code to set up Viewpoint in 3D program Static Matrix LookAtLH ( Vector3 CameraPosition, Vector3 LookingTarget, // (0,0.0) Vector3 UpDirection // (0,1,0) ) device.Transform.View = Viewpoint_Matrix;

5. 5 Actual function private void SetViewpoint() { Matrix viewMatrix = Matrix.LookAtLH ( new Vector3(2.0f, 3.0f, 3.0f), // location of camera new Vector3(0.0f, 0.0f,0.0f), // looking target new Vector3(0.0f, 1.0f,0.0f) // up direction ); device.Transform.View =viewMatrix ; }

6. 6 D3D Projective window After setting up viewpoint, we must setup Projective window, which decided by 4 parameters: i)Float Angle, which means how wide that we can see vertically. ii)Float Ratio of width over height, which can be simply set to be 1.0 if we choose a square viewing window. iii)Near distance, which we usually choose 1.0 iv)Far distance, which we usually choose 100.0 Projective window

7. 7 Projective Matrix Projective matrix is Call the following code to set up Projection in 3D program Static Matrix PerspectiveFovLH ( float angle, //vertical Viewing float Ratio, // width/height float near, // near distance float far// far distance ) device.Transform. Projection = Projective_Matrix;

8. 8 Actual function private void SetProjective() { Matrix ProjMatrix = Matrix.PerspectiveFovLH ( (float)Math.PI / 4, // vertical viewing angle (float)this.Width/(float)this.Height, // ratio 1.0f,// near distance 100.0f// far distance ); m_device.Transform.Projection = ProjMatrix; }

9. 9 Set Rotation In order to make rotation in a constant speed, we need to measure the time elapse by value Environment.TickCount which is the number of milliseconds elapse since the system started. private void SetRotation() { float a = ((float)Environment.TickCount)/1000.0f; float angle = a*2.0f * (float)Math.PI; // one second, 360 degree device.Transform.World = Matrix.RotationY(angle ); // for all objects in 3D world in future drawing } After this function call, all objects in 3D world are rotated around y-axis by same angle

10. 10 RenderState.CullMode device.RenderState.CullMode = Cull.Clockwise ; There are 3 CullMode values for RenderState, which are the mode for the triangle direction. 1)Cull.None draw either directional triangle 2)Cull.Clockwise not draw clockwise triangle 3)Cull.CounterClockwise not draw anticlockwise triangle The following is the code to set CullMode

11. 11 RenderState.Lighting device.RenderState.Lighting = false; The colors of vertices will not be shown in 3D world unless the state of Lighting is set to be false. The following is the code to set Lighting. Later, when we use texture to map picture to triangles, we must set lighting false too. Otherwise all triangle will be black and no picture at all.

12. 12 Set vertex private void SetVertex() { verts = new CustomVertex.PositionColored[3]; verts[0].X=-1.0f;verts[0].Y=0.0f;verts[0].Z=0.0f; verts[0].Color = Color.Yellow.ToArgb(); verts[1].X=1.0f;verts[1].Y=0.0f;verts[1].Z=0.0f; verts[1].Color = Color.Blue.ToArgb() ; verts[2].X=0.0f; verts[2].Y=1.0f;verts[2].Z=0.0f; verts[2].Color = Color.Red.ToArgb(); // the three vertexes of a triangle }

13. 13 private void SetV_Axis() { v_axis = new CustomVertex.PositionColored[5]; v_axis[1].X=0.0f; v_axis[1].Y=0.0f; v_axis[1].Z=0.0f; v_axis[1].Color = Color.White.ToArgb(); // origin (0,0,0, Color.White) v_axis[0]= v_axis[1]; v_axis[2]= v_axis[1]; v_axis[3]= v_axis[1]; v_axis[4]= v_axis[1]; // copy all v_axis[0].X=4.0f; // v[0] & v[1] for drawing x-axis v_axis[2].Y=4.0f; // v[1]& v[2] for drawing y-axis v_axis[3].Z=4.0f; // v[3] & v[4] for drawing z-axis } This function is used to draw 3 axis

14. 14 private bool InitVB() { SetVertex(); VB = new VertexBuffer(typeof(CustomVertex.PositionColored), verts.Length, m_device, 0, CustomVertex.PositionColored.Format, Pool.Default); if(VB==null) return false; VB.Created += new System.EventHandler(this.WriteVertexData); WriteVertexData(null, null); SetV_Axis(); VB2 = new VertexBuffer(typeof(CustomVertex.PositionColored), 5, m_device, 0, CustomVertex.PositionColored.Format, Pool.Default); if(VB2==null) return false; VB2.Created += new System.EventHandler(this.WriteVertexData2); WriteVertexData2(null, null); return true; } // we must separate EventHandler for both vertex buffer Init Vertex Buffers

15. 15 private void WriteVertexData(object sender, EventArgs e) { GraphicsStream stream = VB.Lock(0, 0, 0); stream.Write(verts); VB.Unlock(); } private void WriteVertexData2(object sender, EventArgs e) { GraphicsStream stream = VB2.Lock(0, 0, 0); stream.Write(v_axis); VB2.Unlock(); } VB2 is for drawing axis. Write Data into Vertex Buffer

16. 16 Render function private void Render() { device.RenderState.CullMode = Cull.None; // both directions of triangle are drawn device.RenderState.Lighting = false; // set lighting off SetViewpoint(); // set view point SetProjective();; // set projective window device.Clear(ClearFlags.Target, Color.Black, 1.0f, 0); // clear surface to black color device.BeginScene(); // begin drawing device.VertexFormat = CustomVertex.PositionColored.Format; // set vertex format

17. 17 device.SetStreamSource( 0, VB2, 0); // set stream source device.Transform.World=Matrix.Identity ; // set identity matrix to 3D world device.DrawPrimitives(PrimitiveType.LineList, 0, 1); device.DrawPrimitives(PrimitiveType.LineList, 1, 1); device.DrawPrimitives(PrimitiveType.LineList, 3, 1); // draw 3 axis in fixed position device.SetStreamSource( 0, VB, 0); SetRotation(); // reset rotation matrix device.DrawPrimitives( PrimitiveType.TriangleList, 0, 1); // draw triangle in rotated position device.EndScene(); // end drawing device.Present(); // flip surface } Note: Without setting identity matrix, all axis will be rotating

18. 18 Output We can see three axis and a rotating triangle

19. 19 Two side color triangle private void SetVertex() { verts = new CustomVertex.PositionColored[6]; verts[0].X=-1.0f;verts[0].Y=0.0f;verts[0].Z=0.0f; verts[1].X=1.0f;verts[1].Y=0.0f;verts[1].Z=0.0f; verts[2].X=0.0f; verts[2].Y=1.0f;verts[2].Z=0.0f; verts[0].Color = verts[1].Color = verts[2].Color = Color.Yellow.ToArgb(); verts[3] = verts[0];verts[4] = verts[1];verts[5] = verts[2]; verts[3].Color = verts[4].Color=verts[5].Color = Color.Red.ToArgb(); } If we want to make the triangle to have red color in one side and yellow color in the other side, the code is:

20. 20 Then we use Cull.Mode to make a control private void Render() {...... device.SetStreamSource( 0, VB, 0); // set resource device.RenderState.CullMode=Cull.Clockwise ; device.DrawPrimitives(PrimitiveType.TriangleList, 0, 1); device.RenderState.CullMode=Cull.CounterClockwise ; device.DrawPrimitives(PrimitiveType.TriangleList, 3, 1);...... } // each time we only can draw one triangle

21. 21 private void SetVertex() { verts = new CustomVertex.PositionColored[6]; verts[0].X=-1.0f;verts[0].Y=0.0f;verts[0].Z=0.0f; verts[1].X=1.0f;verts[1].Y=0.0f;verts[1].Z=0.0f; verts[2].X=0.0f; verts[2].Y=1.0f;verts[2].Z=0.0f; verts[0].Color = verts[1].Color = verts[2].Color = Color.Yellow.ToArgb(); verts[3] = verts[0]; verts[4] = verts[2]; verts[5] = verts[1]; // now the direction are different verts[3].Color = verts[4].Color=verts[5].Color = Color.Red.ToArgb(); } Or define the the second triangle with a different direction

22. 22 Then we change Cull.Mode code to private void Render() {...... device.SetStreamSource( 0, VB, 0); // set resource device.RenderState.CullMode=Cull.Clockwise ; device.DrawPrimitives(PrimitiveType.TriangleList, 0, 1); device.DrawPrimitives(PrimitiveType.TriangleList, 3, 1);...... // similarly we only can draw one triangle }