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Shadow Softness - Why is the Spot Light so Different?

mark128mark128 Posts: 1,029
edited December 1969 in New Users

I was fiddling around with the shadow softness on various lights that have the paramater. Distant, point, linear point lights and spot lights all have this parameter. I rendered an image of a 1 meter sphere sitting on a plane to catch the shadows. The lighting is all coming from camera left and down at a 45 degree angle. All lights were set to ray traced shadows. For the lights that have a position, they are 3 meter up and to the left of the sphere center.

I'm showing the results for Distant, Linear Point and Spot light. At first I thought shadow softness was not working at all on the spot light, but if you compare it to a render with softness at 0%, you can see there is a small effect at the edges of the shadows.

The results for the point light are similar to the linear point light, but you have to turn the intensity really high.

I have found if I turn off the limits and increase the shadow softness on the spot light to 2000%, I get something that looks similar to the other lights at 50% softness.

Is there something wrong with spot light? Why does the spot light interpret the meaning of 50% softness so differently?

softCompare.jpg
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Comments

  • JimmyC_2009JimmyC_2009 Posts: 8,891
    edited December 1969

    It does the same for me too, just so as you know you are not alone.

    What I did, was, uncheck Use Limits in the parameters pane, and when I set it to about 4,000%, it worked OK. Must be a bug of some sort, it is not being multiplied properly.

    I don't know that much about lighting, maybe someone else can confirms this.

  • Cayman StudiosCayman Studios Posts: 1,135
    edited December 1969

    My guess is that it is deliberately set that way. Spot lights are directional and are usually used to highlight things from a particular angle, so the softness settings will be gauged with that intention in mind. Point lights are omni-directional, and it would therefore be natural for any object to catch lighting bouncing off all the other objects. These are not "real life physics" lights, but tools designed for specific purposes.

  • Richard HaseltineRichard Haseltine Posts: 101,023
    edited December 1969

    It may be worth making a bug report - if it's meant to be like that they can say so, if not it can be adjusted.

  • prixatprixat Posts: 1,588
    edited August 2013

    The shadow softness looks like a function of the distance, and becomes more noticeable the further away the shadow is.

    In these examples the spheres vary from .2 to .5 meters.

    (With the ground plane lowered, int the second image, all the shadows become distant enough to see some shadow softness.)

    spot2.png
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    spot1.png
    600 x 450 - 201K
    Post edited by prixat on
  • mark128mark128 Posts: 1,029
    edited December 1969

    prixat said:
    The shadow softness looks like a function of the distance, and becomes more noticeable the further away the shadow is.

    In these examples the spheres vary from .2 to .5 meters.

    (With the ground plane lowered, int the second image, all the shadows become distant enough to see some shadow softness.)

    The spot light is producing soft shadows, it is just on a different scale than the distant, point or linear point lights.

    If you put a linear point light at exactly the same location as your spot light and do a render with 50% shadow softness, you will get much softer looking shadows than with the spot light. Same is true of the point light, but you need to turn the intensity up to a few thousand percent on the point light to get the same intensity.

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