Re: How to get 3D coordinates from screen coordinates?
- From: "RP" <rpfi@xxxxxxxxxxxxxx>
- Date: Mon, 2 May 2005 15:41:31 +0100
Thanks
The BaryCentric function works just fine
"Robert Dunlop [MS MVP]" <rdunlop@xxxxxxxx> wrote in message
news:uFV%239iNTFHA.2096@xxxxxxxxxxxxxxxxxxxxxxx
> The point on the intersected triangle is easily calculated from the
> returned barycentric coordinates (U,V) of the intersection and the three
> points that make up the triangle. The point of intersection for U,V
> coordinates returned from IntersectTri with points A,B, and C is:
>
> A + U*(B-A) + V*(C-A)
>
> As a shortcut to this operation you can use the Vector3.BaryCentric
> function (parameters f=U and g=V).
>
> --
> Robert Dunlop
> The X-Zone
> http://www.directxzone.com/
> Microsoft DirectX MVP
> -------------
> The opinions expressed in this message are my own personal views and do
> not reflect the official views of the Microsoft Corporation.
> The MVP program does not constitute employment or contractual obligation
> with Microsoft.
>
> "RP" <rpfi@xxxxxxxxxxxxxx> wrote in message
> news:epGIbazSFHA.1384@xxxxxxxxxxxxxxxxxxxxxxx
>> Hi,
>>
>> Thanks Iain for the reference, I already had seen your previous post but
>> I thought I didn't have to use an intersection ray.
>> Thanks Robert for the theory background that helps me to understand the
>> process of using a vector ray to determine the intersection with a
>> primitive depending of where it is drawn in the frustum.
>> I updated my code, and now I can determine if a click on screen is in or
>> out of a rectangle. I'm using the Geometry.IntersectTri to check both
>> triangles of that rectangle, I'm not sure if it is the best way. but my
>> major concern is how to get the x-coordinates and y-coordinates of that
>> click on screen. I'm using the barycentric coordinates of the
>> IntersectInformation but it becomes a little confusing, and I hope that
>> will be another way to get the coordinates. The coordinates I'm refering
>> are the same that are used to create the vertices in the verts array.
>> In pseudo-code, I'm getting X and Y (this are the coordinates of my
>> vertices, between -2 and 2 for both axis) from U and V like this:
>>
>> Triangle 1:
>>
>> X = width * V + vector[0].X
>> Y = - X + height * U , if x >= 0
>> Y = - X - height * U , if x < 0
>>
>> Triangle 2:
>>
>> Y = - height * V + vector[4].Y
>> X = - Y + height * U , if y >=0
>> X = - Y - height * U , if y < 0
>>
>> Resuming, is the Geometry.IntersectTri the best way to check rectangles?
>> And, more important, after having a positive intersection, how can I
>> retrieve the coordinates X,Y of the point where I clicked?
>>
>> Thanks for your support.
>>
>> Here is the code:
>>
>> using System;
>> using System.ComponentModel;
>> using System.Drawing;
>> using System.Windows.Forms;
>> using Microsoft.DirectX;
>> using Microsoft.DirectX.Direct3D;
>>
>> namespace Chapter3Code
>> {
>> public class Form1 : Form
>> {
>> private CustomVertex.PositionColored[] verts = new
>> CustomVertex.PositionColored[6];
>>
>> private static float camPosX = 0;
>> private static float camPosY = 0;
>> private static float camPosZ = -5;
>> private Device device = null;
>> private VertexBuffer vb = null;
>> private Container components = null;
>>
>> public Form1()
>> {
>> InitializeComponent();
>> this.SetStyle(ControlStyles.AllPaintingInWmPaint |
>> ControlStyles.Opaque, true);
>> }
>>
>> public void InitializeGraphics()
>> {
>> PresentParameters presentParams = new
>> PresentParameters();
>> presentParams.Windowed = true;
>> presentParams.SwapEffect = SwapEffect.Discard;
>> device = new Device(0, DeviceType.Hardware, this,
>> CreateFlags.SoftwareVertexProcessing, presentParams);
>> device.RenderState.FillMode = FillMode.WireFrame;
>> vb = new VertexBuffer(typeof
>> (CustomVertex.PositionColored), 6, device, Usage.Dynamic |
>> Usage.WriteOnly, CustomVertex.PositionColored.Format, Pool.Default);
>> vb.Created += new
>> EventHandler(this.OnVertexBufferCreate);
>> OnVertexBufferCreate(vb, null);
>> }
>>
>> private void OnVertexBufferCreate(object sender, EventArgs e)
>> {
>> VertexBuffer buffer = (VertexBuffer) sender;
>> verts[0].Position = new Vector3(-2, 2, 0.0f);
>> verts[0].Color = Color.Aqua.ToArgb();
>> verts[1].Position = new Vector3(-2, -2, 0.0f);
>> verts[1].Color = Color.Black.ToArgb();
>> verts[2].Position = new Vector3(2, -2, 0.0f);
>> verts[2].Color = Color.Purple.ToArgb();
>> verts[3].Position = new Vector3(-2, 2, 0.0f);
>> verts[3].Color = Color.Aqua.ToArgb();
>> verts[4].Position = new Vector3(2, 2, 0.0f);
>> verts[4].Color = Color.Black.ToArgb();
>> verts[5].Position = new Vector3(2, -2, 0.0f);
>> verts[5].Color = Color.Purple.ToArgb();
>> buffer.SetData(verts, 0, LockFlags.None);
>> }
>>
>> private void SetupCamera()
>> {
>> device.RenderState.CullMode = Cull.None;
>> device.Transform.Projection =
>> Matrix.PerspectiveFovLH((float) Math.PI/4, this.Width/this.Height, 1,
>> 100.0f);
>> device.Transform.View = Matrix.LookAtLH(new
>> Vector3(camPosX, camPosY, camPosZ), new Vector3(camPosX, camPosY, 0), new
>> Vector3(0, 1, 0));
>> device.RenderState.Lighting = false;
>> }
>>
>> protected override void OnPaint(PaintEventArgs e)
>> {
>> device.Clear(ClearFlags.Target, Color.CornflowerBlue,
>> 1.0f, 0);
>> SetupCamera();
>> // Draw a middle point for reference at point (0,0)
>> device.BeginScene();
>> device.VertexFormat =
>> CustomVertex.PositionColored.Format;
>> device.SetStreamSource(0, vb, 0);
>> device.DrawPrimitives(PrimitiveType.TriangleList, 0, 2);
>> device.EndScene();
>> device.Present();
>> this.Invalidate();
>> }
>>
>> protected override void Dispose(bool disposing)
>> {
>> if (disposing)
>> {
>> if (components != null)
>> {
>> components.Dispose();
>> }
>> }
>> base.Dispose(disposing);
>> }
>>
>> #region Windows Form Designer generated code
>>
>> private void InitializeComponent()
>> {
>> this.components = new System.ComponentModel.Container();
>> this.Size = new System.Drawing.Size(640, 480);
>> this.Text = "Form1";
>> }
>>
>> #endregion
>>
>> private static void Main()
>> {
>> using (Form1 frm = new Form1())
>> {
>> frm.Show();
>> frm.InitializeGraphics();
>> Application.Run(frm);
>> }
>> }
>>
>> protected override void OnMouseDown(MouseEventArgs e)
>> {
>> Console.WriteLine("---------------------");
>> Console.WriteLine("(mouse) X=" + e.X);
>> Console.WriteLine("(mouse) Y=" + e.Y);
>>
>> IntersectInformation inside;
>> Vector3 near = new Vector3(e.X, e.Y, 0);
>> Vector3 far = new Vector3(e.X, e.Y, 1);
>> near.Unproject(device.Viewport,
>> device.Transform.Projection, device.Transform.View,
>> device.Transform.World);
>> far.Unproject(device.Viewport,
>> device.Transform.Projection, device.Transform.View,
>> device.Transform.World);
>> far.Subtract(near);
>> if (Geometry.IntersectTri(verts[0].Position,
>> verts[1].Position, verts[2].Position, near, far, out inside))
>> {
>> Console.WriteLine("dist=" + inside.Dist);
>> Console.WriteLine("index=" + inside.FaceIndex);
>> Console.WriteLine("U=" + inside.U);
>> Console.WriteLine("V=" + inside.V);
>> Console.WriteLine("IN-1");
>>
>> float xxx = inside.V*4 + verts[0].Position.X;
>> Console.WriteLine("******XX=" + (xxx));
>> if (xxx >= 0)
>> Console.WriteLine("******YY=" + (-xxx +
>> 4*inside.U));
>> else
>> Console.WriteLine("*****YY=" + (-xxx -
>> 4*inside.U));
>> Console.WriteLine("");
>> }
>> else if (Geometry.IntersectTri(verts[3].Position,
>> verts[4].Position, verts[5].Position, near, far, out inside))
>> {
>> Console.WriteLine("dist=" + inside.Dist);
>> Console.WriteLine("index=" + inside.FaceIndex);
>> Console.WriteLine("U=" + inside.U);
>> Console.WriteLine("V=" + inside.V);
>> Console.WriteLine("IN-2");
>> float yyy = -inside.V*4 + verts[4].Position.Y;
>> Console.WriteLine("******YY=" + (yyy));
>> if (yyy >= 0)
>> Console.WriteLine("******XX=" + (-yyy +
>> 4*inside.U));
>> else
>> Console.WriteLine("*****XX=" + (-yyy -
>> 4*inside.U));
>> }
>> else
>> {
>> Console.WriteLine("OUT");
>> }
>>
>> Console.WriteLine("---------------------");
>> }
>>
>> protected override void OnKeyDown(KeyEventArgs e)
>> {
>> if (e.KeyCode == Keys.Subtract)
>> camPosZ -= 1;
>> else if (e.KeyCode == Keys.Add)
>> camPosZ += 1;
>> else if (e.KeyCode == Keys.Left)
>> camPosX -= 1F;
>> else if (e.KeyCode == Keys.Right)
>> camPosX += 1F;
>> else if (e.KeyCode == Keys.Up)
>> camPosY += 1F;
>> else if (e.KeyCode == Keys.Down)
>> camPosY -= 1F;
>> Console.WriteLine("----------------------------");
>> Console.WriteLine("(cam) X=" + camPosX);
>> Console.WriteLine("(cam) Y=" + camPosY);
>> Console.WriteLine("(cam) Z=" + camPosZ);
>> Console.WriteLine("----------------------------");
>> }
>>
>> }
>> }
>>
>>
>>
>>
>>
>
>
.
- Prev by Date: Re: Performance problem using the Direct3D sprite class
- Next by Date: Resizing and device Lost Event... How to ??
- Previous by thread: Re: Performance problem using the Direct3D sprite class
- Next by thread: Resizing and device Lost Event... How to ??
- Index(es):
Relevant Pages
|
