sunShape intensity does not alter MR scene

[Anonymous]

I created sunDirection/sunShape nodes using the Physical Sun and Sky function in the Scene section of Render Settings (using MR as the Renderer).  All other lights in the scene are switched off.  The color management Apply Output Transform is switched off in the Render Settings

Changing the sunShape Directional Light Intensity attribute changes the amount of light on the scene, as it does change the render results of all other renderers, except the MR renderer.  Why is that so, and can it be changed?

[damaggio]

Hi Francis what do you mean it changes all the other results except MR renderer... Is not very clear since there's only one mental Ray renderer in the scene.

[mspeer]

Hi!

The Directional Light created for Mental Ray Physical Sun and Sky is only intended for changing the light direction (or sun position) in an intuitive way, other settings are ignored. To change light intensity go to the sky shader mia_physicalsky -> Multiplier.

[Anonymous]

Hi Damaggio

You could recognise three 'output' devices: (i) the images in your
viewports, (ii) the results in your render viewer and (iii) the image file
outputs. In my setup, there doesn't seem to be too much similarity between
the render viewer and the image file outputs in terms of brightness. Btw,
the IPR often does not update automatically it seems, injecting more
confusion when you try to figure out the results of changing attribute
settings.



Anyway, I was referring to the fact that the sunShape Intensity is changing
the brightness of the viewport images, but not in the other two. This got
me slightly confused about which node is actually responsible for the amount
of light in the rendered image file. I now believe that it is actually the
mia_physicalsky node and its Multiplier attribute that controls the amount
of light in the rendered files. As the brightness in the render viewer is
not a good indicator for the brightness in the images in the files, it
becomes a bit of a trial-and-error process to find the right attribute
settings.



I hope this makes a bit more sense now?



Cheers

Francis

[Anonymous]

Hi Damaggio

You could recognise three 'output' devices: (i) the images in your
viewports, (ii) the results in your render viewer and (iii) the image file
outputs. In my setup, there doesn't seem to be too much similarity between
the render viewer and the image file outputs in terms of brightness. Btw,
the IPR often does not update automatically it seems, injecting more
confusion when you try to figure out the results of changing attribute
settings.



Anyway, I was referring to the fact that the sunShape Intensity is changing
the brightness of the viewport images, but not in the other two. This got
me slightly confused about which node is actually responsible for the amount
of light in the rendered image file. I now believe that it is actually the
mia_physicalsky node and its Multiplier attribute that controls the amount
of light in the rendered files. As the brightness in the render viewer is
not a good indicator for the brightness in the images in the files, it
becomes a bit of a trial-and-error process to find the right attribute
settings.



I hope this makes a bit more sense now?



Cheers

Francis

[Anonymous]

Hi mspeer,

Thanks for your response. Yes,you're right about the directional light
node. The confusion was about the sunShape node's Intensity attribute (see
my response to adamagio) changing brightness in viewport images, but not
render viewer or render output file images. I guess the Intensity attribute
in the sunShape node is there in case it is not used in combination with the
mia_physicalsky node.



Cheers

Francis

[Anonymous]

Hi mspeer,

Thanks for your response. Yes,you're right about the directional light
node. The confusion was about the sunShape node's Intensity attribute (see
my response to adamagio) changing brightness in viewport images, but not
render viewer or render output file images. I guess the Intensity attribute
in the sunShape node is there in case it is not used in combination with the
mia_physicalsky node.



Cheers

Francis

[damaggio]

Hi Francis, good thing you found out about the multiplier from mspeer response and can now move ahead, one thing to keep in mind though that the viewport 2.0 is still very limited and is not like a real renderer, always test the scene in the render view .

Best.

[Anonymous]

Hi Damaggio,
Thanks for your response and help. My experience is, as mentioned, that the render viewer is not very representative for the rendered results in the output files, at least not in my setup.  I really need to render a couple of scenes  to output files to get an idea of the render results, a time-consuming chore. 
Do you have that experience too?
Cheers
Francis

[damaggio]

it would be just easier then to upload the scene so we can take a look.

[Anonymous]

Hi damaggio,


Sorry for the slow response. I don't know if attachments work, but I
attached a pdf with some test results.

My conclusion from that:

1. The sunShape Intensity attribute changes the camera view but not the
rendering results.

2. The mia_physicalsky1 Multipier attribute changes the rendering
results but not the camera view.



That is quite counter-intuitive, and in combination with

* an IPR region renderer which does not always automatically update,

* a 'stand-alone' directional light's intensity attribute that does
change all render results (of course)

it easily confuse the likes of me, I know it did me.



Apart from the 'sunDirection object does not change the light intensity'
comment (which in its generality is confusing/wrong it seems to me), I have
not been able to find this 'warning' in any of the sun/sky documentation,
tutorials or user comments.



Anyway, thanks again for getting this demystified.



Cheers

Francis

[damaggio]

Are you sure the camera view has the physical sun?....not the perspective camera.

You have to go to camera >Mental ray>Environment shader mia_physicalsky....just drag the Mia into this slot so the second camera gets connected with the physical sky.

[damaggio]

You can zip the file and post here.

[Anonymous]

Hope this works, see attachment.

[Anonymous]

Hi damaggio,

Indeed, you may have a very good point there!!! 

The persp camera does have the mia_physicalsky1 shader in the persp camera MR environmental Shader field (and mia_exposure_simple1 lens shader Maya2016 now automatically adds).  My camera1 does not have anything in those fields.

I understand your suggestion up to a point.  Drag and drop the mia_physicalsky1 shader into camera1 MR environmental Shader field, in the Attribute Editor I assume.  Sorry for my ignorance, but from where do I drag and drop it? Can I just copy/past the text mia_physicalsky1 into that field?

Cheers

[Anonymous]

I just deleted and (re-)created the sun/sky in the MR settings which added the correct mia shader to the persp and cam1 cameras.

However, the behaviour is still the same as described in the previous mail. 

But very good to know that the sun/sky is best generated AFTER your cameras are in place and that cma1 does not inherit these settings from persp.

Cheers

[Anonymous]

Recreating sun/sky does not add the right shader to cam1, you have to add that manually, sorry for the confusion.

[Anonymous]

IGNORE PREVIOUS ENTRY

[Anonymous]

And the scene as requested in an earlier email.

[damaggio · Accepted solution]

Hi Francis, i'm sorry for your troubles, is really a shame that Autodesk provides such shameful documentation, not only the help button does not take you to the relevant page they still haven't fixed the IPR render with physical sun , to get it to work you have to adjust the ground color for the Ipr to pick up the changes, also there's no obvious information to a beginner that they have to lower the exposure way down with the physical sun.

You can save the image from the render view after you made your adjustment with File>Save image>save color managed image

For batch render animation in EXR the images will still be in linear and most likely blown out but since is linear it can be adjusted easily in the comp package.

The physical sun was designed to be very accurate however they don't give you any guidance concerning the right exposure so you have to eyeball it.

Also if you want you can leave the exposure at default and lower quite a bit the multiplier to something like 0.1

HELP DOCS.....Adjust the brightness for display. Lowering the exposure allows you to view detail that is not visible in highlights by default.

You can set a value in the usual ways by using the slider, by typing in the numeric box, or by clicking in the numeric box and dragging with Ctrl + Middle mouse button. In addition, you can:

• Click the icon to toggle between the default and modified values.
• Press Ctrl + Minus to decrease by fine increments.
• Press Ctrl + Alt + Minus to decrease by coarse increments.
• Press Ctrl + = to increase by fine increments.
• Press Ctrl + Alt + = to increase by coarse increments.

This is a diagnostic option that is not saved in the scene. It is not applied to the rendered output, although you can save a color-managed image from the Render View using File > Save Image >

5. The sun and sky shaders should be used in conjunction with final gather. Turn on final gather in the Render Settings window. For more information, see Final Gathering.
   Tip:

   • mia_physicalsky is the main node in the network.
   • The network of nodes is connected to all existing renderable cameras. If you add a new camera after the creation of sun and sky, the network needs to be updated accordingly. See To edit camera connections.
   • It is recommended that you connect an environment shader, such as mib_lookup_spherical, to the Background attribute. Use of a 2D texture may not produce the expected result.

To edit camera connections

1. In some cases, you may create a new camera in your scene after you have created your sun and sky effect. To add this new camera to the sun and sky shader network, select the Update Camera Connections button in the mia_physicalsky Attribute Editor.
2. In other cases, you may wish to detach the sun and sky shader from the renderable camera while retaining the other shader settings and connections. Select the Remove Camera Connections button in the mia_physicalsky Attribute Editor. Do not select the Delete button in the Environment section of the Indirect Lighting tab of the mental ray tabs in the Render Settings window for this purpose. The Delete button completely removes sun/sky from your scene.