AWS Thinkbox Discussion Forums

Reflection pass

Hi

I am doing some light trails in Krakatoa rendering voxels. They are supposed to be long exposure light streaks moving through a city with buildings and cars. The rest of the scene is being rendered with Corona. How can I get a reflection pass to reflect in the Carona scene

I am thinking the best way might be to render a panoramic image sequence from the view of the animated camera and use that as a spherical environment in Carona. How can I render a panoramic from an animated camera in Krakatoa?

Thanks!

In the current 2.6.x build, you cannot render panoramas directly.
But you could create 6 90degree cameras linked to an animated dummy, and aligned to render 6 images in a cubic fashion, then use a 3rd party converter to create a Lat-Long (equirectangular) image from them.
Or you could script a solution that takes a single camera and renders the 6 views automatically without manually building the 6 cameras. Such a script could set the render outputs as needed, and also engage the PCache so that the particles are loaded just once per frame, then rendered from PCache for all 6 views to reduce render times. Then the PCache would be released for the next frame to load the new particles, and repeat…

We are currently working on adding this kind of panorama rendering as a feature of a future version of Krakatoa. It will produce panoramic or 6x1 cubic strips (and even stereo output) automatically. However, you won’t have access to this in the immediate future, so you should consider the above workarounds…

Let me know if you need more help with this!

Oh, another workaround!

You could try rendering the Krakatoa particles as an atmospheric effect in another renderer. In theory, Corona should be able to render the Krakatoa Atmospheric effect in reflections without the need to generate any reflection maps. However, I have never rendered Krakatoa Atmospherics in Corona, so I have no practical experience, and it might not work (let me know if that’s the case).

Basically you should be able to simply add the Krakatoa Atmospheric effect in the 3ds Max Environment dialog, pick the particle sources you were rendering in Krakatoa, tweak the effect’s settings to match the Krakatoa Voxel Renderer settings as close as possible, and render in Corona (or Scanline, VRay, or finalRender which all support Atmospherics). The reflections should “see” the voxels of the atmospheric as they would with any other such effect…

Hi Bobo

Thanks for the advice. The atmospheric effect works well in both Vray and Corona. The color of the Krakatoa atmospheric is inverted for some reason. Do you know why this might be happening? This is an easy fix if I ignore the alpha and invert the render.

Cheers!
E

Hmm, you are obviously doing something special to get that inversion of color, but I have no idea what it is.
Can you step with me through the process of setting this up? What channels did you have in your particles? What options did you define in the Krakatoa Atmospheric? (screenshot please!)

I just tested a simple scene like this:

  • Vray as the renderer
  • Teapot sitting on a Plane
  • VRayLight illuminating the scene
  • Made a PRT Volume from the Teapot
  • Added a Krakatoa Magma to the PRT Volume, set Emission output to 1,1,0 (yellow) value.
  • Assigned a VRayMtl to the Plane, set it to be reflective
  • Added a Krakatoa Atmospheric, opened its UI
  • Picked the PRT Volume as the particle source
  • Checked >Use Emission
  • Added VRayAtmosphere, VRayRawReflection, VRayRawReflectionFilter and VRayReflection (which is the product of the previous two) render elements
  • Rendered in VRay

RESULT: The particles rendered volumetrically with a yellow glow (due to the Emission), and that same yellow color got reflected in the Plane. The Render Elements contained the correct uninverted components of the beauty pass as expected.

To make the particle cloud fully Additive (equivalent to Force Additive on), I modified the Magma to set Color and Absorption to 0,0,0 (black). So now my particles would glow in yellow without leaving any trace in the Alpha, since this suppresses the volumetric shading and does pure additive shading.

Can you try a simple test as outlined above, and see if you are getting different results?

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