vkt camera rotation/transformation

[jsaintauret]

Hello,

I came across this video below, and I would like to know if any one of you knows how I could do this kind of predefined camera rotation/transformation ?
https://user-images.githubusercontent.com/52704901/212181574-d7facbf0-5437-4870-a994-1046cd50af6d.mp4

The main idea That I'm trying like to implement is a way to constraint the render camera axis of rotation when I move the mouse without having to click on "ctrl", similar to what maltab does when you move a 3D plot with the mouse

thank you in advance

[ZiguoAtGitHub]

I think you should add one call_back() function bind to mouse move event.
In the call_back() function you can keep axis-z vertical with setting rotx and roty to zero.

[jsaintauret]

Hi thanks four your answer, I think I get the idea but could you please be more specific with the function I need to use? are rotx and rotz callable vtkcamera function ?

[marcomusy]

yes, there are various ways of doing it... I would first check if any modes works for you out-of-the-box in show(..., mode=...).

• using a callback as Ziguo suggested eg

from vedo import *

def func(event):
    k = event.keypress
    if k=="Right":
        plt.camera.Azimuth(1)
    elif k=="Left":
        plt.camera.Azimuth(-1)
    elif k=="Down":
        plt.camera.Elevation(1)
    elif k=="Up":
        plt.camera.Elevation(-1)
    elif k=="r":
        plt.reset_viewup()
        return
    plt.renderer.ResetCameraClippingRange()
    plt.render()

settings.enable_default_keyboard_callbacks = False
settings.enable_default_mouse_callbacks = False

world = Box(size=(30,15,8)).wireframe()
airplane = Mesh(dataurl+"cessna.vtk").c("green")

plt = Plotter(axes=1)
plt.add_callback("keypress", func)

plt.show(world, airplane, mode="image")

(this uses keypress events)

Or

from vedo import *

def func(event):
    d = event.delta2d
    if d[0] and d[1]:
        return
    if d[0]:
        plt.camera.Azimuth(-d[0])
    if d[1]:
        plt.camera.Elevation(-d[1])
    plt.renderer.ResetCameraClippingRange()
    plt.render()

# settings.enable_default_keyboard_callbacks = False
settings.enable_default_mouse_callbacks = False

world = Box(size=(30,15,8)).wireframe()
airplane = Mesh(dataurl+"cessna.vtk").c("green")

plt = Plotter(axes=1)
plt.add_callback("Interaction", func)

plt.show(world, airplane, mode="image")

(this uses mouse events)

• (more difficult) write a custom https://vtk.org/doc/nightly/html/classvtkInteractorStyle.html

[jsaintauret]

Hi thank you very much for all the tips , I'll try all that and let you know ;)

[ZiguoAtGitHub]

yes, there are various ways of doing it... I would first check if any modes works for you out-of-the-box in show(..., mode=...).

• using a callback as Ziguo suggested eg

from vedo import *

def func(event):
    k = event.keypress
    if k=="Right":
        plt.camera.Azimuth(1)
    elif k=="Left":
        plt.camera.Azimuth(-1)
    elif k=="Down":
        plt.camera.Elevation(1)
    elif k=="Up":
        plt.camera.Elevation(-1)
    elif k=="r":
        plt.reset_viewup()
        return
    plt.renderer.ResetCameraClippingRange()
    plt.render()

settings.enable_default_keyboard_callbacks = False
settings.enable_default_mouse_callbacks = False

world = Box(size=(30,15,8)).wireframe()
airplane = Mesh(dataurl+"cessna.vtk").c("green")

plt = Plotter(axes=1)
plt.add_callback("keypress", func)

plt.show(world, airplane, mode="image")

(this uses keypress events)

Or

from vedo import *

def func(event):
    d = event.delta2d
    if d[0] and d[1]:
        return
    if d[0]:
        plt.camera.Azimuth(-d[0])
    if d[1]:
        plt.camera.Elevation(-d[1])
    plt.renderer.ResetCameraClippingRange()
    plt.render()

# settings.enable_default_keyboard_callbacks = False
settings.enable_default_mouse_callbacks = False

world = Box(size=(30,15,8)).wireframe()
airplane = Mesh(dataurl+"cessna.vtk").c("green")

plt = Plotter(axes=1)
plt.add_callback("Interaction", func)

plt.show(world, airplane, mode="image")

(this uses mouse events)

• (more difficult) write a custom https://vtk.org/doc/nightly/html/classvtkInteractorStyle.html

Awesome reply!

[jsaintauret]

There is a singularity happening when elevation get to 90° it's call "Gimbal Lock" and the plot will have weird behavior. To fix it quickly I have found on internet that you could use plt.camera.OrthogonalizeViewUp() after the plt.camera.Elevation(-d[1]) as a workaround.

[jsaintauret]

Could you please tell me what delta2d stands for ?

[marcomusy]

it's the shift between the previous and current mouse position in 2d units.

[RubendeBruin]

I have a pretty complete custom interactor here: https://github.com/RubendeBruin/DAVE/blob/master/src/DAVE/visual_helpers/vtkBlenderLikeInteractionStyle.py

which does a lot of things, among others keeping the Z-axis vertical.

I still have to contribute this back to vtk but havent found the time to do so. Feel free to use/abuse as you wish.

[marcomusy]

Feel free to use/abuse as you wish.

I abused it by adding it to https://github.com/marcomusy/vedo/blob/master/vedo/interactor_modes.py
;-)
seems to do the job from what i can see!

from vedo import *
settings.enable_default_keyboard_callbacks = False
settings.enable_default_mouse_callbacks = False
mode = interactor_modes.BlenderStyle()
mesh = Mesh(dataurl+"cow.vtk")
plt = Plotter()
plt.show(mesh, axes=1, mode=mode)

[jsaintauret]

Oh very nice!! I'll take a look when I have some time are your going to push it on the next release ? The only thing that I would suggest maybe is that the user could select the preferred control button, in my case I tweak Dave's interact or style to have the rotation/elevation/azimuth control with the left click button on the mouse it's seams more intuitive as opposed to have it with the middle button which is usually the pan zoom.

Would it be hard to have configure control style option?

[marcomusy]

One could do that by passing an option keyword eg something like
mode = interactor_modes.BlenderStyle(use_left_button=True)
but I cannot implement it - you will need to make a PR :)

[jsaintauret]

Ok I'll keep that in mind

[RubendeBruin]

Thanks for the gentle reminder :-) Got me motivated to start on the merge request.
Hopefully it will one day be merged into vtk: https://gitlab.kitware.com/vtk/vtk/-/merge_requests/10128