Spot light with image as a pattern

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DorPrz
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Re: Spot light with image as a pattern

Post by DorPrz » Thu Sep 06, 2018 2:42 pm

BTW after disabling the world light the "bad renders" went completely black.

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B.Y.O.B.
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Re: Spot light with image as a pattern

Post by B.Y.O.B. » Thu Sep 06, 2018 2:45 pm

I rendered 100 images with Path OpenCL and each one was correct.
However I rendered with OpenCL on CPU device because my notebook does not have a GPU.
The fact that it fails on your GPU could mean that your GPU driver has a bug in its OpenCL compiler.

I made some changes as I mentioned, if you want you can test it with the modified file if it also fails on your GPU:
Attachments
untitled (2).blend
(553.25 KiB) Downloaded 44 times
2018-09-06_16-42-24.png
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DorPrz
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Re: Spot light with image as a pattern

Post by DorPrz » Thu Sep 06, 2018 3:05 pm

I had 1 bad render on a CPU, Can you test a little more? maybe 1000 renders?

kintuX
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Re: Spot light with image as a pattern

Post by kintuX » Thu Sep 06, 2018 10:23 pm

Specifically testing Spot Light with image pattern (.bmp) on 100 frames.

It is rendering fine using OCL Path on GTX 1060 6GB.
Sys. specs: driver version 391.74, Windows 7SP1 x64, Blender 2.79b

Just not after first set of changes (applying realistic values).

1. World
=> None

2. Spot Light
Gain = 1
Power (W) = 1500, Efficacy (lm/W) = 17

3. Camera
=> LuxCore Imagepipeline / Tonemapper / Use OpenCL (on)
=> Camera Setings
F-stop: 4, Shutter (s): 1/20, ISO: 400
set-1x100.jpg
Results vary in lighting & 3 black frames.

Have observed similar behavior before, issues when Camera or lights are positioned on XYZ (0,0,0), so i checked coordinates.
Then, after another change: Spot Light moved on X to 0.01, all went smooth. ;) Right.
set-2x100.jpg
Am not sure but, IIRC, it's some kind of bug :?

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Re: Spot light with image as a pattern

Post by B.Y.O.B. » Fri Sep 07, 2018 7:59 am

kintuX wrote:
Thu Sep 06, 2018 10:23 pm
Have observed similar behavior before, issues when Camera or lights are positioned on XYZ (0,0,0), so i checked coordinates.
Then, after another change: Spot Light moved on X to 0.01, all went smooth.
Nice find, this is most likely the cause.
It's probably a bug triggered by numerical precision issues.
In general it is a bad idea to place stuff exactly at the world origin (in any renderer).

The Nvidia OpenCL compiler seems to make the problem more likely.
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