Author Topic: Displacement defects  (Read 7590 times)

2019-07-17, 16:41:06

aler

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Greetings.
When I began to get acquainted with Corona more deeply, noticed that problems arise with Displacement. Very often, it creates defects and to guess the optimal conditions is not easy. For example, inadequate work with bitmap when using tiling with Length U/V. And this is only one of the cases. Below is an visual example. (Cinema 4D R18, Corona 4.1 demo)
It would be nice in the future to fix it. ...or maybe I'm doing something wrong?

2019-07-17, 22:10:12
Reply #1

Designerman77

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Never seen this type of problem with displacement...

Already tried a smaller screen size value?

2019-07-17, 23:02:18
Reply #2

aler

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Already tried probably everything: Screen size (px) - more/less, World size - also different values, with/without Bitmap shader, different output size - 960x600 / 4800x3000, subdiv geometry, etc.... Displacement of the Corona is well displayed only at a great distance. Comparison: displ. VRay vs displ. Corona:

2019-07-18, 10:41:30
Reply #3

romullus

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  • Let's move this topic, shall we?
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I could be wrong, but it looks more like a shading problem, rather than displacement issue. Does that material uses normal map? Try to disconnect it and see if that helps. Also, you may try to turn off autobump feature and see if result will change to the better.
I'm not Corona Team member. Everything i say, is my personal opinion only.

2019-07-18, 13:04:57
Reply #4

aler

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Quote
Does that material uses normal map?
No, normal map there is no.
Quote
Also, you may try to turn off autobump feature and see if result will change to the better.
autobump - where it?
Quote
but it looks more like a shading problem, rather than displacement issue
I also tend to think so. Noticed that the Corona-phong is somewhat inadequate. For comparison: Standard / VRay / Corona.

2019-07-19, 09:36:41
Reply #5

burnin

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Akhm. Apples VS oranges ;)

About this shading issue, you can't really compare Corona (ray tracer)  to AR or VRay (rasterizers).
(short video explaining different rendering methods: raster VS ray trace VS radiosity)

Scientists are working on it... more at SIGGRAPH 2019 - Taming the Shadow Terminator

Possible solutions in short: subdivide more or go with VRay.
e.g.
Low polycount VS High polycount (Subdivision Surface)
VS


:)
« Last Edit: 2019-07-19, 09:40:04 by burnin »

2019-07-19, 12:05:45
Reply #6

aler

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Quote
Possible solutions in short: subdivide more
I do just that :)
And it is not necessary to consider Corona-displacement near, then at a long distance the defects are almost not noticeable.

2019-08-06, 10:12:43
Reply #7

burnin

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@ SIGGRAPH 2019 a paper was presented about technique to overcome terminator issues with PT engines
https://www.yiningkarlli.com/projects/shadowterminator.html

the more you know...