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Darren Hall avatar image
Darren Hall asked ·

C4D Arnold HDRI/Ground Plane Reflection issue

Hello all,

Hope everyone is well? I have a question around ground plane reflection with Arnold and C4D. No matter what options I try I cannot seem to get the correct perspective around ground plane projection reflection. I have looked high and low and so far only found Maya workarounds.

So far I have tried setting up a Ray-Switch network identical to the Maya 2020 solution. Turned on and off shadows in the Tag parameter options for the Shadow-Matte (with and without Ray-Switch Network) which resulted in weird anomalies (pic 2 and 3), despite that often mentioned in posts/tutorials as the go to solution. It appears the only way I can get close is with the Ray-Switch which Arnold for C4D appears to be missing a 'perspective type' option in the projection node? (See Ray-Switch Shader below).

Any help would be appreciated!


Close but no cigar!

Incorrect perspective reflection? (Using Ray-Switch with Spherical type) No 'Perspective type' option available?


Settings:

Tag Parameter shadow option set to 'on', Correct ground plane reflection but black area shows.


Tag parameter shadow option set to 'off' HDRI and ground-plan competing against each other.


Ray-Switch Shader Tree:

I designed 2 test options with 1x being an RGBA Projection, The second a Camera Projection shader. Both identical render results in (top pic).


hdri skydomebackground image
shadow-on.jpg (44.1 KiB)
shadow-off.jpg (46.4 KiB)
ray-switch-tree.jpg (82.9 KiB)
projection.jpg (26.5 KiB)
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Darren Hall avatar image
Darren Hall answered ·

Hello Lee,

Thanks for your feedback! I tried the suggestion from the Arnold but unfortunately I have ended up with another issue in the process. When I apply the background image to the either the Offscreen Colour Link or Offscreen Colour slot it seems to solve the issue but I end up with a sharp edge of the ShadowMatte Plane that is not matched to the HDRI (Circled in red) and a secondary image of the background image (circled in blue)? So in reality I have 3 reflected images on the chrome sphere. 1x HDRI, 1x Ground Plane, 1x Ground Plane in Offsrceen slot?

Is their a way to feather the edge of the ground plane reflection? Or am I looking at this the wrong way?

Cheers

Darren


offset-color.jpg (41.7 KiB)
offset-colour.jpg (15.2 KiB)
shadow-matte.jpg (31.5 KiB)
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Lee Griggs avatar image
Lee Griggs answered ·

Have you tried offscreen_color?

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