IES Light emitter Power and shadow strenght ( solved)

[linvanchene]

Just got a PM asking me about Light emitters and shadow strength.

The basic question was:

How do you adjust the shadow strength of an object affected by a light emitter with IES lights?

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tested with OR 3 alpha 4:

As usual I then started to goof around with various settings to get some kind of grip again how this is all controlled in OctaneRender.

Now I start to wonder if this is really working as intended?

Have a look at the shadow of the cone in those screenshots:

power 41

power 246

power 1130

To be very clear: With shadows I mean the shadow of the cone and NOT the pattern of the IES light.
That strength can be adjusted with the gamme settings of the IES map.

I get that when you raise the power level the shadow starts to converge to a deep "crushed" black while the whites blow out.

But should there not be a visible difference in shadow strength between watt 41 and watt 246?

To me the shadow of the cone at power 41 looks wrong because it is much to strong for such a dimmed light source.
To be more precise what confuses me is the contrast of the IES light produced pattern and the shadow strength of the cone.

Added the test scene:

Light emitter shadow test v1001.orbx

Test scene created with OR 3 alpha 4

(88.62 KiB) Downloaded 134 times

I also tried this at other exposure settings and the results were similar.

Update / Edit:

Ok now I think I got what is bothering me:

It seems the shadow of the cone is in no way affected by the light emitting pattern set in the IES light.

The shadow of the cone is the same shadow strength as if there was no IES light but a simple light emitting plane.

For some reason I was under the impression that different types of IES should produce a different shadow pattern of the objects affected by the light.


- - -

[kavorka]

Correct me if I am wrong, but shouldn't that shadow always be pure black because you don't have any other emitters in your scene and you dont have anything around it to reflect light.

[linvanchene]

Correct me if I am wrong, but shouldn't that shadow always be pure black because you don't have any other emitters in your scene and you dont have anything around it to reflect light.

/sigh - I rushed the test because I quickly wanted to figure this out before retiring for the evening.

Thank you for helping out! You are right.

Just the indirect light rays bouncing off the ground plane were not enough to actually observe the effect of indirect light as it would happen in an enclosed room.

Adding a cube to the scene solved the issue.

Now the indirect rays are more visible in the shadow area depending on both

- power of the light emitter

- gamma level of the IES