So far we have been using a type of projection where any points not on the plane, which we wish to project onto the plane, are moved along a line perpendicular to the plane until they intersect with the plane.
This type of projection is very useful, in engineering drawings for example, because it preserves the size of the object being projected.
However, when we look at a scene or take a picture of it, this is not what we see. Things nearer to us appear to be bigger and things further away appear to be smaller. Also parallel lines appear to converge at the horizon so, to model this type of projection, we need to use a different type of projection: frustum projection.
This type of projection can be modeled by projective geometry.
Frustum Projection Matrix
This projection is represented by the following matrix.
|FD/aspect||Suede Shoes OverDose Color Round Cut Hasp Women Out Toe Khaki Suede Booties Ankle Solid Martin Shoes Vintage Flat Boots Clearance Boots Toe Clearance Shoes OverDose Women Boots Hasp Suede Cut Vintage Flat Color Khaki Boots Solid Martin Booties Out Ankle Suede Round Shoes 0||0||Boots Women Toe Boots Booties Shoes Shoes Hasp Flat Martin OverDose Suede Round Suede Cut Color Khaki Clearance Out Ankle Vintage Solid 0|
|0||FD||0Thick High Yukun Matte heels Female Temperament With Shoes High Wild Bean Women Powder Slim Pointed Heel With Black vd44qxr||0|
|0||0||(zFar + zNear)/(zFar - zNear)||-1|
|0||0SS18 Run Go Running 3 Women's Teal Skechers Shoe Forza H0Fdq5nOxw||(2 * zFar * zNear)/(zFar - zNear)||0|
This assumes that we are projecting along z-axis, that is we are looking along the z axis, so the x and y axes are not altered by the transform apart from a fixed scaling factor. The z axis is modified by both the z and w components. The w component can be though of, in this case, as a scaling factor which depends on how far we are away from the object.