Possible to allow off-center zengl.camera ortho projection?

[d-orm]

I have been experimenting with using zengl.camera with fov=0 for a ortho lighting projection matrix, and found that it's much better performance than using numpy or glm - however, it seems like we can only specify size as an integer, whereas with numpy/glm we can specify left/right/top/bottom.

This seems to mean that the corner of the projection area is always centered to my shadow map texture, and needs to be twice as big as I need it in order to cover the whole scene, thus reducing the shadows quality.

It'd be great if it was possible to specify left/right/top/bottom instead of just size.

[szabolcsdombi]

size as an integer

it should allow float.

This seems to mean that the corner of the projection area is always centered to my shadow map texture, and needs to be twice as big as I need it in order to cover the whole scene, thus reducing the shadows quality.

please explain this.

I made this fov=0 specially for shadow maps and i had no problems with this so far.

do you need width!=height or do you need something special where left != -right && top != -bottom

Isn't size and aspect enough?

BTW i only render to square power of to shadow maps

[szabolcsdombi]

See: https://github.com/szabolcsdombi/zengl/blob/main/zengl.c#L3499-L3500

this allows non square images.

you can actually make off center work from glsl by adding a vec2 to .xy of the result after multiplying with the camera matrix.
this should also work:

gl_Position = camera_matrix * my_vec4
gl_Position.xy += vec2(1.0, 1.0) // this translates from -size, size range to 0, size -- i did not test this code, += might need to be -=

[d-orm]

This seems to mean that the corner of the projection area is always centered to my shadow map texture, and needs to be twice as big as I need it in order to cover the whole scene, thus reducing the shadows quality.

please explain this.

So when using numpy for my ortho matrix, I am setting the ortho params to the below:

ortho_params={
    "left": -22.0,
    "right": 56.0,
    "bottom": -53.0,
    "top": 1.0,
    "near": -15.0,
    "far": 42.0,
}

Tweaking the l/r/b/h sizes so my scene covers the full shadow texture as below:

But when I use:

zengl.camera(
    eye=self.eye,
    target=self.target,
    up=self.up,
    aspect=1,
    fov=0,
    near=self.ortho_params["near"],
    far=self.ortho_params["far"],
    size=30.0,
)

The corner of the shadow map is always centered as below:

So I then needed to double the size from 30 -> 60 to cover the full scene, but also doubles the resolution/wastes a bunch of space and decreases the shadow quality:

[d-orm]

I think adding the vec2 to offset it in the vertex shader sounds like it should work though and is a nice idea, will try this & report back!

[d-orm]

the glsl offset works great! (it was indeed += 😄) I have the offset dimensions as uniforms now so I can tweak them along with the size to fit my scene perfectly too, as I could with the numpy version.

thank you!

[szabolcsdombi]

Cannot you just set a different eye and target values to get a different center?
here:

zengl.camera(
    eye=self.eye,
    target=self.target,
    up=self.up,
    aspect=1,
    fov=0,
    near=self.ortho_params["near"],
    far=self.ortho_params["far"],
    size=30.0,
)

[szabolcsdombi]

I see you usually just set target and eye to be something and tweak left and right until the full scene is just covered.

I use blender for this:

this is an area light. I usually use blender python console to export position, target and area size.

[d-orm]

Cannot you just set a different eye and target values to get a different center?

I'm relatively new to this stuff, but playing around with the target/eye without using the glsl offset just seemed to spin/pivot the projection around whilst still keeping the corner of it centered to the shadow map texture.

I don't have much experience with Blender, but will check out the light stuff in it at some point - I'm working with a directional/sun light at the moment and am building a level editor where the size of the scene can be dynamic, so it's useful to be able to tweak the light projection on the fly. Will share some progress on it on discord soon :)

[szabolcsdombi]

seeng only the corner sounds weird Will check. It can be an implementation issue. I reopen until then