# Is the OpenGL orthographic projection matrix the same?

## Is the OpenGL orthographic projection matrix the same?

The OpenGL Orthographic Projection Matrix Source Code A Simple Perspective Matrix A word of warning again. The matrix we will present in this chapter is different from the projection matrix that is being used in APIs such as OpenGL or Direct3D. Though, it technically produces the same results.

## How does a perspective projection matrix work in CG?

All we need to do to get a basic perspective projection matrix working, is to account for the angle of view or field-of-view (FOV) of the camera. We know that by changing the focal length of a zoom lens on a real camera, we can change how much we see of a scene (the extent of the scene). We want our CG camera to work in the same way.

How can I determine the projection of a layer?

As you will later see, the project’s CRS may not match the layer’s CRS. To determine a layer’s projection, we can look into the metadata. Right click on ne_10m_admin_0_countries layer and select Properties. Switch to the Metadata tab in the Layer Properties dialog. Expand the Properties section.

### Do you have to do matrices in GLSL?

Well, in fact, you almost never do this in GLSL. Most of the time, you use glm::translate () in C++ to compute your matrix, send it to GLSL, and do only the multiplication : This one is special. It doesn’t do anything. But I mention it because it’s as important as knowing that multiplying A by 1.0 gives A. Scaling matrices are quite easy too :

### How does the projection matrix work in OpenGL?

At the heart of things, the orthographic projection matrix will still convert things to the [-1, 1] range, since that’s what OpenGL expects. It just provides a way to adjust our coordinate space, so that we can see more of our scene if the screen is wider, and less if the screen is narrower.

All we need to do to get a basic perspective projection matrix working, is to account for the angle of view or field-of-view (FOV) of the camera. We know that by changing the focal length of a zoom lens on a real camera, we can change how much we see of a scene (the extent of the scene). We want our CG camera to work in the same way.

Is the projection matrix of a linear model idempotent?

The projection matrix corresponding to a linear model is symmetric and idempotent, that is, P 2 = P {displaystyle mathbf {P} ^{2}=mathbf {P} } . However, this is not always the case; in locally weighted scatterplot smoothing (LOESS), for example, the hat matrix is in general neither symmetric nor idempotent.

#### How are x y and W divided in OpenGL?

Each coordinate in OpenGL actually has four components, X, Y, Z, and W. The projection matrix sets things up so that after multiplying with the projection matrix, each coordinate’s W will increase the further away the object is. OpenGL will then divide by w: X, Y, Z will be divided by W.