Camera Lens Shift Game Engine #38451

New Issue

reilly donovan · 2014-02-02T19:16:25+01:00

reilly donovan commented

2014-02-02 19:16:25 +01:00

System Information
Operating system and graphics card
OSX 10.9 IntelHD 3000

Blender Version
Broken: (example: 2.69.7 4b206af, see splash screen)

Short description of error
I can't seem to get the script described here to work for the BGE:
http://wiki.blender.org/index.php/Doc:2.6/Manual/Game_Engine/Camera#Camera_lens_shift

To manipulate the projection we can then directly modify the camera projection matrix in Python.

import bge
scene = bge.logic.getCurrentScene()
cam = scene.active_camera

get projection matrix

camatrix = cam.projection_matrix

modifying the camera projection matrix by modifying the x and y terms of the 3rd row to obtain a shift of the rendered area

camatrix- [x]- [x] = 2shiftx
camatrix- [x]- [x] = 2shitfy
cam.projection_matrix = camatrix
Here in field of view units are shiftx and shifty. So for example, for shifting the view up half a screen shifty is set to 0.5.

Note that a camera's projection_matrix attribute may not be set until after initialization scripts are executed and running this code immediately after the game starts will mess up the projection matrix.

This last sentence doesn't make much sense to me, could someone help clarify the workflow for properly executing this script for the BGE? Thank you so much!

Exact steps for others to reproduce the error
Based on a (as simple as possible) attached .blend file with minimum amount of steps

**System Information** Operating system and graphics card OSX 10.9 IntelHD 3000 **Blender Version** Broken: (example: 2.69.7 4b206af, see splash screen) **Short description of error** I can't seem to get the script described here to work for the BGE: http://wiki.blender.org/index.php/Doc:2.6/Manual/Game_Engine/Camera#Camera_lens_shift To manipulate the projection we can then directly modify the camera projection matrix in Python. import bge scene = bge.logic.getCurrentScene() cam = scene.active_camera # get projection matrix camatrix = cam.projection_matrix # modifying the camera projection matrix by modifying the x and y terms of the 3rd row to obtain a shift of the rendered area camatrix- [x]- [x] = 2*shiftx camatrix- [x]- [x] = 2*shitfy cam.projection_matrix = camatrix Here in field of view units are shiftx and shifty. So for example, for shifting the view up half a screen shifty is set to 0.5. Note that a camera's projection_matrix attribute may not be set until after initialization scripts are executed and running this code immediately after the game starts will mess up the projection matrix. This last sentence doesn't make much sense to me, could someone help clarify the workflow for properly executing this script for the BGE? Thank you so much! **Exact steps for others to reproduce the error** Based on a (as simple as possible) attached .blend file with minimum amount of steps

reilly donovan commented

2014-02-02 19:16:25 +01:00

Changed status to: 'Open'

reilly donovan commented

2014-02-02 19:16:25 +01:00

Added subscriber: @Reilly

Adam Friesen commented

2014-02-02 23:20:13 +01:00

Added subscriber: @Ace_Dragon

Adam Friesen commented

2014-02-02 23:20:13 +01:00

According to the wiki

Camera Lens Shift

In the Blender interface, there is an option to shift the camera view on the x/y plane of the view. It is comparable to lens shift in video projectors that usually shift the image up along the Y axis. So for example, when you put the beamer on a table it does not project half of the image on the table.

Unfortunately, this parameter is not taken in account by the Game Engine.

I can't say for sure, but it almost sounds like one of those old functions that have been broken longer than anyone could remember (hence why it's actually mentioned in the wiki). Though it would be nice to get it working again providing it has use over just moving the position of the camera itself with Python (since it's in the bge.logic module).

According to the wiki *`Camera Lens Shift`* In the Blender interface, there is an option to shift the camera view on the x/y plane of the view. It is comparable to lens shift in video projectors that usually shift the image up along the Y axis. So for example, when you put the beamer on a table it does not project half of the image on the table. **Unfortunately, this parameter is not taken in account by the Game Engine.** I can't say for sure, but it almost sounds like one of those old functions that have been broken longer than anyone could remember (hence why it's actually mentioned in the wiki). Though it would be nice to get it working again providing it has use over just moving the position of the camera itself with Python (since it's in the bge.logic module).

Angus Hollands commented

2014-02-02 23:57:01 +01:00

Added subscriber: @AngusHollands-4

Angus Hollands commented

2014-02-02 23:57:01 +01:00

Note that a camera's projection_matrix attribute may not be set until after initialization scripts are executed and running this code immediately after the game starts will mess up the projection matrix.

This means the camera must be rendered from first in order to correctly initialise the internal matrices:

See this patch of mine which also addresses an aspect of this issue - it will allow the matrix to be updated first frame and then used therearfter https://developer.blender.org/T36617

Note that a camera's projection_matrix attribute may not be set until after initialization scripts are executed and running this code immediately after the game starts will mess up the projection matrix. This means the camera must be rendered from first in order to correctly initialise the internal matrices: See this patch of mine which also addresses an aspect of this issue - it will allow the matrix to be updated first frame and then used therearfter https://developer.blender.org/T36617

Campbell Barton commented

2014-02-27 13:52:29 +01:00

Added subscriber: @ideasman42