icepic1984

05-14-2011, 06:27 AM

Hi!

Im reading the orange book at the moment and i have a

small problem.

To transform incoming vertices to eye-space they suggest

the following method:

in vec4 vertex;

uniform mat4 mvmatrix;

vec4 epos;

vec3 epos3;

void main() {

...

epos = mvmatrix * vertex;

epos3 = (vec3(epos)) / epos.w

}

What does the last line do? My vertices are available in homogeneous

coordinates, but the fourth component is always 1 so i could just

write epos.xyz to get the same result or am i wrong?

Later in the book there are several examples where the author use this

method. But from time to time he divided the transformed vertex by w

and i don't know why.

Can someone help me out?

Im reading the orange book at the moment and i have a

small problem.

To transform incoming vertices to eye-space they suggest

the following method:

in vec4 vertex;

uniform mat4 mvmatrix;

vec4 epos;

vec3 epos3;

void main() {

...

epos = mvmatrix * vertex;

epos3 = (vec3(epos)) / epos.w

}

What does the last line do? My vertices are available in homogeneous

coordinates, but the fourth component is always 1 so i could just

write epos.xyz to get the same result or am i wrong?

Later in the book there are several examples where the author use this

method. But from time to time he divided the transformed vertex by w

and i don't know why.

Can someone help me out?