In this entry I thought I’d setup a basic HDRI + backplate scene in different render engines and start a discussion on workflows. The scenario is simple, you have a backplate image, and environment HDRI. You want to incorporate some CG elements into the backplate in one render, compositing not required. I will provide the files so you can see how the scene is configured & see if I’ve overlooked anything.
So, let’s begin.
Corona Render (CPU):
3ds Max file: http://jeffpatton.net/share/Corona_Basic_Comp.zip
Outline: In Corona Render you’ll setup a ground plane with a shadow catcher material. Assign the backplate to the scene environment or Direct Visibility Override. Then assign the HDR to the scene environment.
Pros: Simplicity, good results, able to render everything in one pass including color controls like LUT, bloom/glare, and tone mapping.
Cons: Can be difficult to get reflected light/caustics from CG elements.
3ds Max file: http://jeffpatton.net/share/iray+_Basic_Comp.zip
Outline: In iRay+ you’ll setup an environment light source and assign the environment HDRI to it (enable shadows on the ground/shadow option). Assign the backplate to the scene environment.
Pros: Simple to configure. Their environment light is a neat approach to configuring IBL.
Cons: Difficult to get reflected light/caustics from CG elements. In other applications I can adjust the gamma/contrast on the HDRI to strengthen the ground shadows. That is locked in iray+ so the shadows here don’t match up as well. Yes, I could adjust the HDRI outside of 3ds Max for iray+, but that’s not the point here. It also needs glare/bloom/LUT options.
Arion Render (GPU):
3ds Max file: http://jeffpatton.net/share/Arion_Basic_Comp.zip
Outline: In Arion Render you assign the HDRI and backplate to the Arion IBL light source and enable the matte floor option in the settings.
Pros: Able to render everything in one pass including color controls like LUT, bloom/glare, and tone mapping.
Cons: Difficult to get reflected light/caustics from CG elements. Apparently the ground shadows don’t pick up HDRI illumination, it’s just an ambient occlusion type shadow.
Octane Render (GPU):
3ds Max file: http://jeffpatton.net/share/Octane_Basic_Comp.zip
Outline: In Octane Render you assign the HDRI to the scene environment via texture environment shader. There isn’t a simple method for implementing the backplate.
Pros: Fast. Nice looking results. Glow/Bloom and LUT options.
Cons: Not as easy to get the CG elements incorporated into a backplate in one pass/shot. You can either render the CG elements out with an alpha channel and/or passes and use a 3rd party program to comp the CG elements. I have used (incorrectly I’m sure) the diffuse material to make a ground and backplate with projected textures to pick up the shadows so I could render everything together without having to composite the 3d elements.
3ds Max file: http://jeffpatton.net/share/VRay_Basic_Comp.zip
Outline: In VRay you can assign the HDRI to a VRay dome light. There are material & VRay setting options for a matte/shadow catcher. The backplate can be assigned to the scene environment.
Pros: Nice looking results with bounced light onto the backplate. Glow/Bloom and LUT options.
Cons: None / Previous issues appear to be resolved in the latest release.
VRay RT (GPU):
3ds Max file: (same as VRay above, just switch it over to RT as the engine)
Outline: Same as VRay above.
Pros: Nice looking results with bounced light onto the backplate and it didn’t require any changes from VRay CPU. Glow/Bloom and LUT options.
Cons: A lot of the previous issues appear to be resolved in the latest release.
FStorm (GPU): *DEMO*
3ds Max file: http://jeffpatton.net/share/FStorm_Basic_Comp.zip
Outline: In FStorm you assign the HDRI to the environment option of FStorm settings. Then assign your backplate to the new Alpha Environment settings introduced in version 1.1.4b.
Pros: Fast. LUT, Bloom/Glare, and color control options. Simple to configure. Fast development speed
Cons: The shadow catcher doesn’t pick up the color from the HDRI, but it can be tinted in post. Depth of field doesn’t seem to impact the alpha backplate. However, that too can be adjusted in post with a z-depth pass.
mental ray (CPU)
3ds Max file: http://jeffpatton.net/share/mentalray_Basic_Comp.zip
Outline: In mental ray you’ll assign the HDRI to a skylight light. Assign a matte/shadow/reflection material to the ground plane. The backplate can be assigned to the scene environment directly or via the environment/background switcher.
Pros: Nice looking results and simple to configure. It comes free with 3ds Max.
Cons: Nothing major. Bounced light and/or caustics can be configured but it’s not automatic. Would be nice to have LUT & glow/glare options built into the frame buffer.
3ds Max file: http://jeffpatton.net/share/REDSHIFT_Basic_Comp.zip
Outline: In Redshift you’ll add a redshift dome light to the scene and configure the HDRI and backplate within that. Very straight forward.
Pros: Render speed, out of core rendering for complex scenes that won’t fit on your GPU. Fairly easy to use.
Cons: As someone with no experience with this render engine I spent more time trying to figure out how to add DOF than anything else. Turns out you have to add a Redshift Bokeh effect to the scene effects and configure it there. That’s fine, but I’d prefer to see DOF controls either in camera or in the render settings. It also seems like the Redshift shadow catcher doesn’t pick up colored shadows. I had to manually set the shadow color to a blueish hue. That too is ok, at least it’s adjustable. Just something to mention. IMHO it would be nice to have the LUT/glow/bloom options in Redshift as well.
iRay (GPU version included with 3ds max):
3ds Max file: http://jeffpatton.net/share/iray_Basic_Comp.zip
Outline: In iRay you’ll need to add a light source to your scene and disable it to prevent the default lighting from illuminating the scene. From there, if you’re using 3ds Max 2015 like me, you’ll have to run the gauntlet of unhiding/unlocking the matte/environment shader. Hopefully this just works in newer versions than I’m using. Assign the iray matte environment to the scene environment and then add your HDRI & backplate to an environment & background switcher and nest it inside the iray matte environment shader.
Pros: Fast. It comes with 3ds Max. Good results.
Cons: Those freakin’ hidden shaders & cryptic string options…oh man, I could scream. If it’s a feature of a program how about providing simple access to it via the UI for the love of all that is holy. Oh, it also needs glare/bloom/LUT options. 🙂
There is nothing wrong with compositing 3d elements onto backplates outside of 3ds Max. Sometimes that’s the most efficient way to handle a specific project or task. I’m simply listing the workflows for different applications where the goal is to render directly onto a backplate. A “one and done” type scenario if you will.