On Thursday, 3 September 2020 at 12:36:35 UTC, Thomas wrote:
My example code:
---------------------
import std.stdio;
int main()
{
import gfm.math.matrix;
const int width = 800;
const int height = 600;
auto projectionMatrix = mat4!(float).identity();
auto ratio = cast(float)width / cast(float)height;
projectionMatrix = mat4!(float).perspective( 45.0f, ratio,
0.0f, 100.0f );
writeln("projectionMatrix: ", projectionMatrix );
auto inversedMatrix = mat4!(float).identity();
inversedMatrix = projectionMatrix.inverse(); // <-- why
this does not work ?
writeln("inversedMatrix: ", inversedMatrix );
return 0;
}
This is not the problem, but FYI these two lines are reduntant:
auto projectionMatrix = mat4!(float).identity();
auto inversedMatrix = mat4!(float).identity();
This is all you need:
auto projectionMatrix = mat4!(float).perspective( 45.0f, ratio,
0.0f, 100.0f );
auto inversedMatrix = projectionMatrix.inverse();
`perspective` and `inverse` return new instances that overwrite
the two identity matrices you initialized, so you're doing work
you don't need to do.
The projection matrix will be calculated correctly with
[1.34444, 0, 0, 0, 0, 1.79259, 0, 0, 0, 0, -1, -0, 0, 0, -1, 0]
assuming that the screen size is 800x600.
But using the .inverse() function in gfm returns only a matrix
with following values:
[-nan, -nan, -nan, -nan, -nan, -nan, -nan, -nan, -nan, -nan,
-nan, -nan, -nan, -nan, inf, -inf]
I don't know what I am doing wrong here:
- do I call the function wrong way ? (but there is no other
way)
- is there a bug in the function ? (I do not believe that
because the library is battle proved)
My guess is the problem is in the `inverse` implementation:
https://github.com/d-gamedev-team/gfm/blob/master/math/gfm/math/matrix.d#L448
T invDet = 1 / det;
It doesn't check if det is 0.
This shows 1f / 0f results in `inf`:
import std;
void main()
{
float f = 0;
float i = 1 / f;
writeln(i);
}
https://run.dlang.io/is/ZyggRg
With all those zeroes in the perspective matrix and all the
multiplications in the `inverse` function, I guess things are
getting wonky.
