question

Tino Nettling avatar image
Tino Nettling asked ·

Spec Intensity goes wild

Hi i'm facing an issue wich happens in Arnold 4 (alSurface) and 5 (aiStandardsurface)

If i'm creating a shader with metal intensity 1 and a plain directional light with intensity of 1 it results in specular values of upto 500! This value decreases by increasing the radius/angle of the light - in my simple example i had to use an angle of 60 to get the spec values to something around 1.

If i use a skydomelight the specular intensity values matches the intensity of the light. Wich is what i would expect.

Why is that?

What can i do to tame the the spec intensity ? Clamping would be my last option.

thanks for any input

arnoldarnold5lightshader
10 |600 characters needed characters left characters exceeded

Up to 5 attachments (including images) can be used with a maximum of 2.0 MiB each and 9.8 MiB total.

Zeno Pelgrims avatar image
Zeno Pelgrims answered ·

This is because it's relative to the solid angle of the light. A skydome will distribute the values over the whole hemisphere whilst a directional light will contain it within it's angular value.

If you'd capture the value of the sun on a reflective sphere, you'd see exactly the same behaviour.

To work around this you can do multiple things:

- Create a rougher material, pretty much everything in real life has imperfections
- Create a less reflective material, most materials are not nearly as reflective as you'd think in real life - even metals.
- Increase the solidangle of the light

You should avoid clamping at all costs in this situation.

Share
10 |600 characters needed characters left characters exceeded

Up to 5 attachments (including images) can be used with a maximum of 2.0 MiB each and 9.8 MiB total.

Girijashankar Senapati avatar image
Girijashankar Senapati answered ·

Yah. If feel same. Render setting clamping option would be better.

Share
10 |600 characters needed characters left characters exceeded

Up to 5 attachments (including images) can be used with a maximum of 2.0 MiB each and 9.8 MiB total.

Write an Answer

Hint: Notify or tag a user in this post by typing @username.

Up to 5 attachments (including images) can be used with a maximum of 2.0 MiB each and 9.8 MiB total.

Welcome to the Arnold Answers community.

This is the place for Arnold renderer users everywhere to ask and answer rendering questions, and share knowledge about using Arnold, Arnold plugins, workflows and developing tools with Arnold.

If you are a new user to Arnold Answers, please first check out our FAQ and User Guide for more information.

When posting questions, please be sure to select the appropriate Space for your Arnold plugin and include the plugin version you are using.

Please include images, scene and log files whenever possible as this helps the community answer your questions.

Instructions for generating full verbosity log files are available for MtoA, MaxtoA, C4DtoA, HtoA, KtoA, and Kick.

If you are looking for Arnold Documentation and Support please visit the Arnold Support site.

To try Arnold please visit the Arnold Trial page.

Bottom No panel present for this section.