units of scene affect the renderer #52182

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opened 2017-07-24 23:10:03 +02:00 by Sasha · 21 comments

Units of scene affect the renderer. Need to change coefficient of lighting reduction with change unit preset. when I am modeling, i need change units of scene to metric -> cm (0.01) and when I am rendering, I have to set strength lighting for sun: coofStgangeINeed and for point 1/(0.01*0.01)*coofStgangeINeed.
I did not find where to write, so write here.
sory my bad English.

Units of scene affect the renderer. Need to change coefficient of lighting reduction with change unit preset. when I am modeling, i need change units of scene to metric -> cm (0.01) and when I am rendering, I have to set strength lighting for sun: coofStgangeINeed and for point 1/(0.01*0.01)*coofStgangeINeed. I did not find where to write, so write here. sory my bad English.
Stuart Broadfoot was assigned by Sasha 2017-07-24 23:10:03 +02:00
Author

Changed status to: 'Open'

Changed status to: 'Open'
Author

Added subscriber: @2saniok2

Added subscriber: @2saniok2
Stuart Broadfoot was unassigned by Brecht Van Lommel 2017-07-24 23:27:01 +02:00

Added subscriber: @broadstu

Added subscriber: @broadstu

Removed subscriber: @broadstu

Removed subscriber: @broadstu

Added subscriber: @brecht

Added subscriber: @brecht

Normally Cycles render results are not affected when changing the units. I don't know how to reproduce this problem, it seems to work as expected for me.

Can you attach a .blend file where changing the units in the Scene properties and then pressing F12 gives a different result? Also which operating system and Blender version are you testing with?

Normally Cycles render results are not affected when changing the units. I don't know how to reproduce this problem, it seems to work as expected for me. Can you attach a .blend file where changing the units in the Scene properties and then pressing F12 gives a different result? Also which operating system and Blender version are you testing with?
Author

I meant that Cycles is based on real dimensions in real units, but in the blender users can change units of scene in the scene (meters centimeters, and so on), and when the time comes to render, the scaled scene renders inaccurately as the light fades out not linearly My opinion is to enter in the Cycles the scaling factor of the scale or to make clarity with the scale units in Blender.
When you select units in cm, then simulate and then change to meters, then the model will increase by 100 times, but it is only necessary to change the prefix from cm to m and change the number that is displayed on the screen and not scale the model relative to the scene.
In my opinion, the bug is in Blender and not in Cycles, but Blender needs to change everything from the center, and therefore, it is necessary to Check the scale-dependent scene modules based on Blender, therefore it is possible to enter the coeficient in Cycles temporarily to solve this problem, before solving it in Blender.

I meant that Cycles is based on real dimensions in real units, but in the blender users can change units of scene in the scene (meters centimeters, and so on), and when the time comes to render, the scaled scene renders inaccurately as the light fades out not linearly My opinion is to enter in the Cycles the scaling factor of the scale or to make clarity with the scale units in Blender. When you select units in cm, then simulate and then change to meters, then the model will increase by 100 times, but it is only necessary to change the prefix from cm to m and change the number that is displayed on the screen and not scale the model relative to the scene. In my opinion, the bug is in Blender and not in Cycles, but Blender needs to change everything from the center, and therefore, it is necessary to Check the scale-dependent scene modules based on Blender, therefore it is possible to enter the coeficient in Cycles temporarily to solve this problem, before solving it in Blender.
Author

Зняток екрану як 2017-07-25 22-38-31.png

Зняток екрану як 2017-07-25 22-29-00.png

![Зняток екрану як 2017-07-25 22-38-31.png](https://archive.blender.org/developer/F678794/Зняток_екрану_як_2017-07-25_22-38-31.png) ![Зняток екрану як 2017-07-25 22-29-00.png](https://archive.blender.org/developer/F678793/Зняток_екрану_як_2017-07-25_22-29-00.png)

Changed status from 'Open' to: 'Archived'

Changed status from 'Open' to: 'Archived'
Brecht Van Lommel self-assigned this 2017-07-25 21:43:11 +02:00

Ok, this is more about the unit system in general then like the discussion in D1799.

There is nothing inaccurate about the Cycles render when changing units. If for example m is changed to cm, then light intensities can be interpreted as changing from Watt to centiwatt, and measures like irradiance (Watts/m^2) are not sensitive to distance units anyway. Light falloff stays physically correct regardless of units, it's always quadratic.

Ok, this is more about the unit system in general then like the discussion in [D1799](https://archive.blender.org/developer/D1799). There is nothing inaccurate about the Cycles render when changing units. If for example m is changed to cm, then light intensities can be interpreted as changing from Watt to centiwatt, and measures like irradiance (Watts/m^2) are not sensitive to distance units anyway. Light falloff stays physically correct regardless of units, it's always quadratic.

I'm not sure what you did in that test, but here I don't see any differences in the render results when changing units? Blender units only affect how the value is displayed in the UI, not the actual render.

Eventually we want to support displaying W and W/m^2 units for lights so this is a bit more clear.

I'm not sure what you did in that test, but here I don't see any differences in the render results when changing units? Blender units only affect how the value is displayed in the UI, not the actual render. Eventually we want to support displaying W and W/m^2 units for lights so this is a bit more clear.
Author

in thouse example plane and point has been scaled. Please pay attention at the grid size.

In #52182#448137, @2saniok2 wrote:
Зняток екрану як 2017-07-25 22-38-31.png

Зняток екрану як 2017-07-25 22-29-00.png

in thouse example plane and point has been scaled. Please pay attention at the grid size. > In #52182#448137, @2saniok2 wrote: > ![Зняток екрану як 2017-07-25 22-38-31.png](https://archive.blender.org/developer/F678794/Зняток_екрану_як_2017-07-25_22-38-31.png) > > ![Зняток екрану як 2017-07-25 22-29-00.png](https://archive.blender.org/developer/F678793/Зняток_екрану_як_2017-07-25_22-29-00.png)
Author

But, for your result (without scaling)
Зняток екрану як 2017-07-25 23-27-41.png

But, for your result (without scaling) ![Зняток екрану як 2017-07-25 23-27-41.png](https://archive.blender.org/developer/F678834/Зняток_екрану_як_2017-07-25_23-27-41.png)
Author

Changed status from 'Archived' to: 'Open'

Changed status from 'Archived' to: 'Open'
Sasha reopened this issue 2017-07-25 23:37:35 +02:00
Author

beacose Cycles works winth Blender_Unit (I think)
and need B_U convert to meters

beacose Cycles works winth Blender_Unit (I think) and need B_U convert to meters

You are not taking into account that the units of light emission changed. You assume they stay in Watt, but they changed to centiwatt.

You are not taking into account that the units of light emission changed. You assume they stay in Watt, but they changed to centiwatt.

Changed status from 'Open' to: 'Archived'

Changed status from 'Open' to: 'Archived'
Author

but not in square

but not in square

Ok, then assume they changed to 10^-4 W, since W = kg * m^2 / s^3. The point remains the same, Cycles should not compensate for this, rather Blender should display the proper units.

Ok, then assume they changed to 10^-4 W, since W = kg * m^2 / s^3. The point remains the same, Cycles should not compensate for this, rather Blender should display the proper units.
Author

This comment was removed by @2saniok2

*This comment was removed by @2saniok2*
Author

then problem in 3DviewPort, (grid and unit we see), Because blender changes the units to expand the range, and Improve quality. PS. The difference between imperial and metric is not taken into account

then problem in 3DviewPort, (grid and unit we see), Because blender changes the units to expand the range, and Improve quality. PS. The difference between imperial and metric is not taken into account
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