CODEWITHSUNDEEP
c#3dxnacamera
Mehdi Bugnard
Mehdi Bugnard

Reputation: 3979

How to move the camera behind a model with the same angle?

I meet are having difficulty in moving my camera behind an object in a 3D world. I would create two view mode.

1: for fps (first person). 2nd: external view behind the character (second person).

I searched the net some example but it does not work in my project.

Here is my code used to change view if F2 is pressed

 //Camera
        double X1 = this.camera.PositionX;
        double X2 = this.player.Position.X;
        double Z1 = this.camera.PositionZ;
        double Z2 = this.player.Position.Z;


        //Verify that the user must not let the press F2
        if (!this.camera.IsF2TurnedInBoucle)
        {
            // If the view mode is the second person
            if (this.camera.ViewCamera_type == CameraSimples.ChangeView.SecondPerson)
            {
                this.camera.ViewCamera_type = CameraSimples.ChangeView.firstPerson;

                //Calcul position - ?? Here my problem
                double direction = Math.Atan2(X2 - X1, Z2 - Z1) * 180.0 / 3.14159265;
                //Calcul angle - ?? Here my problem

                this.camera.position = ..
                this.camera.rotation = ..

                this.camera.MouseRadian_LeftrightRot = (float)direction;
            }
            //IF mode view is first person
            else
            {
                    //....

Upvotes: 1

Views: 1027

Answers (2)

Steve H
Steve H

Reputation: 5519

Here is a very basic 3rd person camera (what you meant by 2nd person) in Xna. It assumes you have the player's world matrix stored and can access it:

Vector3 _3rdPersonCamPosition = playerWorldMatrix.Translation + (playerWorldMatrix.Backward * trailingDistance) + (playerWorldMatrix.Up * heightOffset);// add a right or left offset if desired too
Vector3 _3rdPersonCamTarget = playerWorldMatrix.Translation;//you can offset this similarly too if desired
view = Matrix.CreateLookAt(_3rdPersonCamPosition, _3rdPersonCamTarget , Vector3.Up);

If your FPS cam is working properly and assuming it is essentially the same location and orientation as the player, you can substitute it's view matrix in place of the playerWorldMatrix above like this:

Matrix FPSCamWorld = Matrix.Invert(yourWorkingFPSviewMatrixHere);

Now wherever I wrote playerWorldMatrix you can use FPSCamWorld instead.

Upvotes: 1

JerKimball
JerKimball

Reputation: 16904

If I were you, I would take your now-working FPS camera (I'm assuming that moves properly, has a positional matrix, etc?), and add another Translation Transform to it to "move it" back behind the player.

Put another way:

If your "translation/view matrix" for the FPS view is something like:

(sorry, haven't played with XNA in a while, so don't remember proper class names) 

var camTranslateMatrix = [matrix representing player position];
var camDirectionMatrix = [matrix representing player direction, etc];
var camViewMatrix = camTranslateMatrix * camDirectionMatrix;

Then you could change it like so:

var camTranslateMatrix = [matrix representing player position];
var camDirectionMatrix = [matrix representing player direction, etc];

// If not in 3rd person, this will be identity == no effect
var camThirdPersonMatrix =
       IsInThirdPersonMode ?
             new TranslateMatrix(back a bit and up a bit) :
             IdentityMatrix();

var camViewMatrix = 
      camTranslateMatrix * 
      camDirectionMatrix * 
      camThirdPersonMatrix;

Make sense? That way, it'd be trivial to toggle between the two views without tons of nasty math each time you do so.

Upvotes: 1

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