Set Up a View Matrix

(^_^,只能看到projection以后棱錐上下截面間的部分)
The three input vectors represent the following, respectively:

1. The eye point: [0, 3, -5].???? (眼睛)
2. The camera look-at target: the origin [0, 0, 0]. (眼睛要看的東東)
3. The current world's up-direction: usually [0, 1, 0].?? (指出那邊是上面)

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using ?Microsoft.DirectX.Direct3D;

Device?device? = ? null ;?? // ?Create?rendering?device.

// ?Set?up?the?view?matrix.?A?view?matrix?can?be?defined?given?an?eye?point,
// ???a?point?to?view,?and?a?direction?for?which?way?is?up.?Here,?you?set?
// ???the?eye?five?units?back?along?the?z-axis?and?up?three?units,?view?the
// ???origin,?and?define?"up"?to?be?in?the?y-direction.

device.Transform.View? = ?Microsoft.DirectX.Matrix.LookAtLH(
???????????????????????????? new ?Vector3( 0.0f ,? 3.0f ,? - 5.0f ),
???????????????????????????? new ?Vector3( 0.0f ,? 0.0f ,? 0.0f ),
???????????????????????????? new ?Vector3( 0.0f ,? 1.0f ,? 0.0f ));

This example demonstrates how to set up the projection transformation matrix, which transforms 3-D camera or view space coordinates into 2-D screen coordinates.

See the following C# code example, the Projection transformation matrix is set to be equal to the left-handed (LH) PerspectiveFovLH matrix. Input arguments to PerspectiveFovLH are as follows.

1. Field of view in radians: pi/4. (一般都為1/4 pi)
2. Aspect ratio, or view-space height divided by width: 1, for a square window. (長(zhǎng)寬的比)
3. Near clipping plane distance: 1 unit.???? (離眼睛近的點(diǎn),即棱錐的上面)
4. Far clipping plane distance: 100 units.? (離眼睛遠(yuǎn)的點(diǎn),即棱錐的下面)

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using?Microsoft.DirectX;

Direct3D.Device?device?=?null;??//?Create?rendering?device.

//?For?the?projection?matrix,?you?set?up?a?perspective?transform?(which
//???transforms?geometry?from?3-D?view?space?to?2-D?viewport?space,?with
//???a?perspective?divide?making?objects?smaller?in?the?distance).?To?build
//???a?perspective?transform,?you?need?the?field?of?view?(1/4?pi?is?common),
//???the?aspect?ratio,?and?the?near?and?far?clipping?planes?(which?define?
//???the?distances?at?which?geometry?should?no?longer?be?rendered).

device.Transform.Projection?=?Matrix.PerspectiveFovLH(
??????????????????????????????(float)Math.PI?/?4,?1.0f,?1.0f,?100.0f?);

What Is a World Transformation?

A world transformation changes coordinates from model space, where vertices are defined relative to a model's local origin, to world space, where vertices are defined relative to an origin common to all of the objects in a scene. In essence, the world transformation places a model into the world; hence its name.

Setting Up a World Matrix

As with any other transformation, you create the world transformation by concatenating a series of transformation matrices into a single matrix that contains the sum total of their effects. In the simplest case, when a model is at the world origin and its local coordinate axes are oriented the same as world space, the world matrix is the identity matrix. More commonly, the world matrix is a combination of a translation into world space and possibly one or more rotations to turn the model as needed.

The following C# code example, from a fictitious 3-D model class written in C#, creates a world matrix that includes three rotations to orient a model and a translation to relocate it relative to its position in world space.

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public?class?ModelClass
{
???private?float?xPos=0;
???private?float?yPos=0;
???private?float?zPos=0;

???private?float?Pitch=0;
???private?float?Yaw=0;
???private?float?Roll=0;

???//Other?model?properties?and?methods
???
???public?Matrix?MakeWorldMatrix(Matrix?worldMatrix)
???{
??????worldMatrix.Translate(xPos,yPos,zPos);

??????Matrix?matRot?=?Matrix.Identity;

??????matRot.RotateYawPitchRoll(Yaw,Pitch,Roll);
??????
??????worldMatrix?=?Matrix.Multiply(matRot,?worldMatrix);

??????return?worldMatrix;

???}
}