Hi, I'm new on Direct3D using DirectX 9.

I have following problem:

I want to display a carstesian coordinate system with x-y-z.

When I'm looking in x-Direction orthogonal on the y-z plane, I want to have e.g. that '1' on the z-axis matches to physically '10 millimeter' on the screen. I.e. the distance of point1 = (0, 0, 0) to point2 = (0, 0, 1) should be after rendering 10 mm on the screen.

Is this possible? If yes, can you give me a tip how I can achieve this?

Hint: When drawing with GDI something in 2D the mapping mode would allow me to calculate how many pixels are required to draw a line with a length of 10 millimeter.

But with Direct3D I have no idea how this can be achieved, because all points will be put in a rendering/transformation pipeline and afterwards Direct3D draws all at it's own.

Thanks!

@Nik02
Thanks much for your answer!

I don't completely understand it all.
I agree, that it's not possible to get physical dimensions of a surface.

But (please look at attached drawing):
assuming a line starting from point_1 (0,0,0) and ending at point_2 (0, 0, 1) will be rendered finally to the line point_1s (0,0) - point_2s (0, 100) on the screen, then for the z-Values a certain mapping from 3D-points to Screen-Points is given: for 96 dpi, then 100 pixels were approximately 1 inch.
Vice versa: I'm looking for a transformation-matrix or solution where I can say I want to have 100 pixels (~ 1 inch) should correspond to 1 z-unit in my 3D-space.
A use case may be, that the user may print with this setting, so he has on his paper afterwards e.g. a cube with 1 inch per side.

Has anyone an idea how I could solve this problem?

Thanks!