Very slow Area-lamp (in viewport, on GPU-device)

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S0rda
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Very slow Area-lamp (in viewport, on GPU-device)

Post by S0rda » Fri May 10, 2019 6:20 pm

Please answer, why is the area lamp so slow in the viewport (besides, I can move all other sources of lighting without problems), just like the mesh with the lighting (emission) shader?
Slightly faster when rendering on the processor.
My system is 6800k and 1080ti.

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Re: Very slow Area-lamp (in viewport, on GPU-device)

Post by B.Y.O.B. » Fri May 10, 2019 6:39 pm

Behind the scenes an area light is a meshlight in LuxCore. The exporter creates a plane with two triangles with the dimensions specified in the area light settings.
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S0rda
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Re: Very slow Area-lamp (in viewport, on GPU-device)

Post by S0rda » Fri May 10, 2019 7:02 pm

Okay. And why is it so extremely slow? I rotate the environment maps without problems without any problems (2k resolution), but the mesh (1 polygon with 4 vertices) creates large lags.

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Re: Very slow Area-lamp (in viewport, on GPU-device)

Post by Dade » Fri May 10, 2019 7:10 pm

S0rda wrote:
Fri May 10, 2019 7:02 pm
Okay. And why is it so extremely slow? I rotate the environment maps without problems without any problems (2k resolution), but the mesh (1 polygon with 4 vertices) creates large lags.
It needs to rebuild the BVH, how many triangles do you have in the scene ? Does it happen with a simple scene too ?
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S0rda
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Re: Very slow Area-lamp (in viewport, on GPU-device)

Post by S0rda » Fri May 10, 2019 7:20 pm

1. Sphere (2 million polygons)
2. "background" lighting with flat-color (very low value of gain - only for non-absolutly dark scene))
3. one or two area-lamps
4. I can't remember if I tested it in previous projects. It seems to be just the slowness in the previews that was the reason, even on scenes in a total of 300-500k polygons.

S0rda
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Re: Very slow Area-lamp (in viewport, on GPU-device)

Post by S0rda » Thu May 16, 2019 12:18 pm

Any reaction?

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Re: Very slow Area-lamp (in viewport, on GPU-device)

Post by Fox » Thu May 16, 2019 1:10 pm

Turn off blender undo memory. Blender will save new copy with every move or mouse click you make, while it does, the ui will be frozen. When you have high poly model, the frozen time is noticeable.
Set the viewport path depth to 1 or 2 for speed.
Split the blender viewport in 4 and drag the preview window small enough for good fps.
The official Blender 2.79b has really bad default openGL settings, in Windows at least, (tune this down).

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Re: Very slow Area-lamp (in viewport, on GPU-device)

Post by Dade » Thu May 16, 2019 6:55 pm

S0rda wrote:
Fri May 10, 2019 7:20 pm
1. Sphere (2 million polygons)
2. "background" lighting with flat-color (very low value of gain - only for non-absolutly dark scene))
3. one or two area-lamps
4. I can't remember if I tested it in previous projects. It seems to be just the slowness in the previews that was the reason, even on scenes in a total of 300-500k polygons.
Rebuilding a BVH with 2M triangles is not a trivial task but Embree is very fast so it is hard to say without doing some comparison. I would expect to be very fast with a cube (i.e 12 triangles, not 300-500k) and to become progressively slower more triangles there are on the scene :?:
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