Unexpected $vpr behavior
JordanBrown wrote
I'm not quite sure what the constraint is or what it deeply means, but as
long
as you're centered on the origin ($vpt=[0,0,0]; look at the bottom of
the window) you can't get the Z axis to appear off vertical. (It can
tilt towards you or away from you, but never left or right.)
Jordan, try Shift-drag.
Bruce,
Try this with Animate;
cube([100,10,10]);
cylinder(r=5,h=100,center=true);
$vpr=[$vpr[0],$vpr[1],$t*360];
Then drag & shift-drag. Note the rotate=[] at the bottom of the window.
Noting $vpr=[?,?,nnn] rotates AROUND Z.
Replace the third value with $vpr[2], then use $t360 in X then Y.
Then make all three $t360.
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Here is a better one;
Rotate_x=false;
Rotate_y=false;
Rotate_z=false;
cube([100,10,10]);
cylinder(r=5,h=100,center=true);
$vpr=[ (Rotate_x) ? $t360 : $vpr.x,
(Rotate_y) ? $t360 : $vpr.y,
(Rotate_z) ? $t*360 : $vpr.z];
Show customizer, then select which axis to rotate dynamically.
Select one at a time, then use the Top/Bottom/Left/Right/Front/Back cube
buttons to explore what is rotating.
Now, the Viewport axes are X - left/right, Y - up/down, that is related to
the screen.
Now I see what bmihuraca is on about.
You would expect Z to then be AROUND the viewport depth axis, but it rotates
around the 3d-space X/Y plain.
Hmmm...
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The viewport's depth axis is Y, not Z. If you rotate Y (which you can't do
with your mouse, but you can do with $vpr), the Z axis will tilt in the
display. X is pitch, Y is roll, Z is yaw.
On December 8, 2020 at 15:19:13, MichaelAtOz (oz.at.michael@gmail.com)
wrote:
Here is a better one;
Rotate_x=false;
Rotate_y=false;
Rotate_z=false;
cube([100,10,10]);
cylinder(r=5,h=100,center=true);
$vpr=[ (Rotate_x) ? $t360 : $vpr.x,
(Rotate_y) ? $t360 : $vpr.y,
(Rotate_z) ? $t*360 : $vpr.z];
Show customizer, then select which axis to rotate dynamically.
Select one at a time, then use the Top/Bottom/Left/Right/Front/Back cube
buttons to explore what is rotating.
Now, the Viewport axes are X - left/right, Y - up/down, that is related to
the screen.
Now I see what bmihuraca is on about.
You would expect Z to then be AROUND the viewport depth axis, but it
rotates
around the 3d-space X/Y plain.
Hmmm...
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stupid...
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Domain; to the extent possible under law, I have waived all copyright and
related or neighbouring rights to this work. Obviously inclusion of works
of previous authors is not included in the above.
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I will say, though, that given this, it's odd that $vpr = [0, 0, 0] gives
you a top-down view. [0, 0, 0] being a front view would be more
consistent...
On December 8, 2020 at 15:33:14, Whosawhatsis (whosawhatsis@gmail.com)
wrote:
The viewport's depth axis is Y, not Z. If you rotate Y (which you can't do
with your mouse, but you can do with $vpr), the Z axis will tilt in the
display. X is pitch, Y is roll, Z is yaw.
On December 8, 2020 at 15:19:13, MichaelAtOz (oz.at.michael@gmail.com)
wrote:
Here is a better one;
Rotate_x=false;
Rotate_y=false;
Rotate_z=false;
cube([100,10,10]);
cylinder(r=5,h=100,center=true);
$vpr=[ (Rotate_x) ? $t360 : $vpr.x,
(Rotate_y) ? $t360 : $vpr.y,
(Rotate_z) ? $t*360 : $vpr.z];
Show customizer, then select which axis to rotate dynamically.
Select one at a time, then use the Top/Bottom/Left/Right/Front/Back cube
buttons to explore what is rotating.
Now, the Viewport axes are X - left/right, Y - up/down, that is related to
the screen.
Now I see what bmihuraca is on about.
You would expect Z to then be AROUND the viewport depth axis, but it
rotates
around the 3d-space X/Y plain.
Hmmm...
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stupid...
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Domain; to the extent possible under law, I have waived all copyright and
related or neighbouring rights to this work. Obviously inclusion of works
of previous authors is not included in the above.
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Whosawhatsis wrote
If you rotate Y (which you can't do with your mouse, but you can do with
$vpr), the Z axis will tilt in the
display.
You can with shift-drag.
Do Reset-view, then View-top.
Then shift-drag with left-right movement, it rotates about the screen
up-down axis while looking at rotate=[] at the bottom of the screen, Y
changes. Then Reset-view, ie diagonal, do the same drag.
The viewport's depth axis is Y, not Z.
Do View-top, then move mouse to bottom/right corner, drag toward
bottom-left,
ie rotate around depth, see rotate=[], Z changes.
X is pitch, Y is roll, Z is yaw.
Like graph paper,
left-right is the X-axis, thus rotate-X = pitch,
up/down is the Y-axis, rotate-Y = roll,
top/bottom is Z-axis, rotate-Z should = viewport yaw,
but changing $vpr Z does not yaw the viewport, it yaws the 3D-space Z-axis.
Play with that code & customizer, select only Rotate_Z, click view-left.
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On 12/8/2020 3:18 PM, MichaelAtOz wrote:
You would expect Z to then be AROUND the viewport depth axis, but it rotates
around the 3d-space X/Y plain.
So far it seems totally consistent to me.
Each rotation rotates the object around the specified axis - whichever
way that axis points right now. (But first offset by $vpt.)
The key thing is that if you have [ rx, 0, rz ] it first rotates
around the X axis and then rotates around the Z axis.
Since rotating around the X axis moves the Z axis off vertical, rotating
around Z causes the X axis line to move on the screen.
I think that's the effect that Bruce is talking about.
Bruce: if you keep the Y and Z rotations zero, I think you'll see that
rotating around X works exactly as you expect. Similarly, if you keep
the Z rotation zero, rotating around Y works as you expect (even if X
rotation is non-zero).
I suspect that it is a deep philosophical question whether what is
happening is that the universe is turning (around $vpt) while the camera
remains still, or if the camera is orbiting $vpt while continuing to
point at it.
What it definitely isn't is turning the camera. The camera always
points at $vpt.
I think.
On 12/8/2020 5:32 PM, Jordan Brown wrote:
On 12/8/2020 3:18 PM, MichaelAtOz wrote:
You would expect Z to then be AROUND the viewport depth axis, but it rotates
around the 3d-space X/Y plain.
So far it seems totally consistent to me.
Each rotation rotates the object around the specified axis - whichever
way that axis points right now. (But first offset by $vpt.)
The key thing is that if you have [ rx, 0, rz ] it first rotates
around the X axis and then rotates around the Z axis.
Since rotating around the X axis moves the Z axis off vertical,
rotating around Z causes the X axis line to move on the screen.
... moves the Z axis off of screen vertical ...
I think that's the effect that Bruce is talking about.
Bruce: if you keep the Y and Z rotations zero, I think you'll see
that rotating around X works exactly as you expect. Similarly, if you
keep the Z rotation zero, rotating around Y works as you expect (even
if X rotation is non-zero).
I suspect that it is a deep philosophical question whether what is
happening is that the universe is turning (around $vpt) while the
camera remains still, or if the camera is orbiting $vpt while
continuing to point at it.
What it definitely isn't is turning the camera. The camera always
points at $vpt.
I think.
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Yes MichaelAtOz,
That is a good demo of what I am getting at.
Bruce
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