**gluLookAt**(...) which helps you position the viewer (camera) inside your scene.What this matrix does is to transform points from world space into camera space - or in other words in it answers this question:

*"What would be the coordinate of a world point if the camera was the origin of a new world coordinate system?".*WebGL does not have it in its API, so let's create our own from scratch then.

You need three things to construct a view matrix:

**eye**of the camera - position of the camera specified in world coordinates.**target**point**-**indicates the target of the camera (where we want to look).**up**vector - defines which direction is*up*.

You also need to remember that the up vector must not be parallel to the line of sightvector from the eye to the target point!

*Eye, target and up vector.*

And here is the pseudo-code for constructing the view matrix:

**{**

*Matrix lookAt(Vector3 eye, Vector3 target, Vector3 up)*Vector3 vz= normalize(eye - target);

Vector3 vx = normalize(crossProduct(up, vz));

// vy doesn't need to be normalized because it's a cross

// product of 2 normalized vectors

Vector3 vy = crossProduct(vz, vx);

Matrix inverseViewMatrix = new Matrix(new Vector4(vx, 0),

new Vector4(vy, 0),

new Vector4(vz, 0),

new Vector4(eye, 1));

*return inverseViewMatrix.getInverse();*}

First of all two important assumptions I have in this code:

- eye, target and up are 3-component vectors - this is not the general case
- I assume that the matrix mode is row-major - the matrix mode only affects in which order you multiply matrices and vectors, the result stays the same

Nice work:D

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ReplyDeleteplease post the derivation of view matrix

ReplyDeleteHi. How do you know what target point is in the first place?

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