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Thread: Portal Lights question

  1. #1
    Curmudgeon in Training Ma3rk's Avatar
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    Portal Lights question

    In short, can Portal Lights use Cast Shadows?

    I've been working on an interior set & think this is a good candidate to use Portal Lights. Went the Wiki, read the page & got the sample scenes. I start with the Teapots_PortalOFF & read the notes then moved on to the Teapots_PortalON scene. At first it looks normal & I select the Portal Light & Properties panel. I enabled the cast shadows & went back to the Basic tab. If you now toggle Portal, the scene goes black.

    It's the Cast Shadows option. Enabled, scene goes black & renders black.

    Since I've never worked with them before, is this bug or feature? I am using 2019.1.3.
    "Never be a cat in a cartoon. Never." Chief Wiggum

  2. #2
    Yes - Portal lights cast shadows. Don't forget to use the dropdown to troubleshoot renders.

    Click image for larger version. 

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    Tim Parsons
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  3. #3
    Curmudgeon in Training Ma3rk's Avatar
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    But do you use the Enable in the Shadows Tab for the Portal light? That's the question.

    They seem to work w/o it so wondering if they're taking that info from the enviro light and that carries over to the Portal. So if Shadows then gets enabled in the Portal properties, is it sort of triple-double-daring the situation & getting everything confused? That make any sense?

    Similar situation to the Primitive lights when taking the color from the objects surface, where it's multiplicative rather than additive.

    Oh, I've been using the Buffers view.

    Problem area I'm having is in the Indirect Diffusion actually, so ya the GI contribution. I'm cheating a bit now & adding some motivated ies lights; Arri L-7's actually.
    "Never be a cat in a cartoon. Never." Chief Wiggum

  4. #4
    did you turn off shadow options for the glass object in render properties, just a thought

    Actually just went and checked an old scene with a portal light and lo and behold scene turned black, but not when I turned on cast shadows for the portal light, happened when I then moved to a second light in the scene, so I would say bug, scene does recover if you click around enough turning lights on and off but it shouldn't be doing that.
    Last edited by gerry_g; 09-18-2019 at 04:03 AM.

  5. #5
    Right, final word, far as I can see Ngon as a Portal = ok , Area light as a Portal = fail,(displays ok with vpr but renders black) why I have no idea, possibly Area light now being single sided causing an unforeseen problem , who knows, but its a bug

  6. #6
    Curmudgeon in Training Ma3rk's Avatar
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    Interesting gerry_g. I might try experimenting with that.
    "Never be a cat in a cartoon. Never." Chief Wiggum

  7. #7
    Everything works as expected here. The VPR and F9 are the same. Raytrace Shadows works as expected. The NGon light works properly as well as the Area light.
    Tim Parsons
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  8. #8
    Curmudgeon in Training Ma3rk's Avatar
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    No, not Raytraced Shadows Tim. Cast Shadows option in the Lights Properties:

    Click image for larger version. 

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    "Never be a cat in a cartoon. Never." Chief Wiggum

  9. #9
    Quote Originally Posted by Ma3rk View Post
    No, not Raytraced Shadows Tim. Cast Shadows option in the Lights Properties:

    Click image for larger version. 

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    Oh - I see. Still works as expected. It's just not updating VPR, so they need to fix that. Renders as expected though.
    Tim Parsons
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  10. #10
    Curmudgeon in Training Ma3rk's Avatar
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    Quote Originally Posted by Tim Parsons View Post
    Oh - I see. Still works as expected. It's just not updating VPR, so they need to fix that. Renders as expected though.
    Mine renders black.
    "Never be a cat in a cartoon. Never." Chief Wiggum

  11. #11
    Here's my setup. A distant light acting as a sun and then a portal light on the exterior of the building directing light into and through the window. Renders fine with cast shadows on or off. The last image is a test with an NGon light with 3 sides and as you can see there is a triangle shadow.

    Click image for larger version. 

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    Not sure what's going on on your end, but everything seems to be working fine here. - With the exception of VPR not updating and needed a nudge on the timeline.
    BTW - I've tested this on two different PC's with the same results.
    Tim Parsons
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    Sauder Woodworking Co.

    http://www.sauder.com

  12. #12
    Curmudgeon in Training Ma3rk's Avatar
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    Actually, your first image seems to be exhibiting the problem For now, I'm just gonna leave it off until some can 'splain the logic.

    Do you know if Portals start bloating render time even if they aren't "in the shot"? This model is huge and I've been lighting a room as I go & seems to be getting taking longer now.
    "Never be a cat in a cartoon. Never." Chief Wiggum

  13. #13
    Quote Originally Posted by Ma3rk View Post
    Actually, your first image seems to be exhibiting the problem For now, I'm just gonna leave it off until some can 'splain the logic.

    Do you know if Portals start bloating render time even if they aren't "in the shot"? This model is huge and I've been lighting a room as I go & seems to be getting taking longer now.
    Not sure if they add any render time as apposed to regular lights, but you can get away without using GI in some cases. I think everything is working as expected and I made a video to see if that helps.
    Tim Parsons
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    Sauder Woodworking Co.

    http://www.sauder.com

  14. #14
    Curmudgeon in Training Ma3rk's Avatar
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    Thanks for that Tim. What is your ceiling area & Dist Light set to intensity wise?
    "Never be a cat in a cartoon. Never." Chief Wiggum

  15. #15
    Goes bump in the night RebelHill's Avatar
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    Quote Originally Posted by Tim Parsons View Post
    A distant light acting as a sun and then a portal light on the exterior of the building directing light into and through the window.
    Thats not how portal lights work in LW... they're basically just areas lights, and in portal mode will trace to the backdrop for their colour.

    Quote Originally Posted by Ma3rk View Post
    For now, I'm just gonna leave it off until some can 'splain the logic.
    Of course it renders black... the cast shadow option makes the light behave like an object which itself casts a shadow from other lights... by turning it on in your scene, you're basically just turning it into a polygon blocking the distant light.
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