Power Work Session

Today, I had a pretty successful work session. Between this post and the last one, there will be a huge jump in progress. But really, I've been making really rough progress all week. Now, I have perfected them.

Compositing is a key topic in this class. So, when compositing CG objects onto a live action plate, it is best to break apart the CG object into layers. These layers allow the compositor to make further, smaller adjustments to the rendered images and makes matching the plate that much easier.

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The Layers

Shadow
Inside: Ground, Sphere & Spot light
Shaders: AiShadowMatte on Ground

Direct Diffuse
Inside: Sphere & Spot light
Shader: AiStandardSurface with specular weight set to 0.

Direct Specular
Inside: Sphere & Spot Light
Shader: ​AiStandardSurface with diffuse weight set to 0.

Indirect Lighting
Inside: Sphere, Ground, and HDR
​Shader: AiStandardSurface

Bounce Shadow
​Inside: Sphere, Ground, Spot Light
​Shader: AiShadowMatte on Ground and Spot light's Specular visibility is set to 0.

Shadow Prep
​Inside: Ground
​Shader: SurfaceShader
Note: Rendered from a camera in same position of spot light (Light Camera). Use image for Shadow Projection layer.

Shadow Projection
​Inside: Ground, and Sphere
​Shader: SurfaceShader
Note: Used render from the Shadow Prep layer and projected image from the Light Camera. Inverted Image color.

Beauty
​Inside: Ground, HDR, Spot light and Sphere
Use: This layer was created to compare Arnold's AOV passes with the layer passes.

Occlusion Sphere
​Inside: Ground, and Sphere
​Shader: AiAmbientOcclusion

Occlusion Ground
​Inside: Ground, and Sphere
​Shader: AiAmbientOcclusion
Use: This is the darkest part of the shadow that is directly under the object. This part of the shadow is not necessarily connected with the light.

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Compositing in Nuke

Bring these layers together in nuke, and create a beautiful and readable tree. One side of my tree focuses on the sphere while the other side focuses on the shadow.

​This final composite looks pretty good other than the shadow. The Shadow feels a little out of place.

The goal of the assignment is to match both real and CG sphere. However, the lighting between my clean plate and sphere plate changed just enough to make things a little more challenging. If I were to brighten the key light, it would blow out the sphere and cause hot spot. I would attempt to change 

the diffuse color, but I know what the real sphere looks like and that's a light grey color. So when I took the picture, the sphere is actually being blown out by the sun. In the end, I favored making the CG sphere feel more integrated over completely matching the light. For the next class, I will see what suggestions I should try to get them to match better.

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Problems to Solve

Just to get a head a bit, I did some quick animation test where the two sphere roll through the scene. Further back in the frame, the shadow projection gets repeated creating random streaks on the sphere. One 

way around this would be to paint the image used for this projection. The other option is to not have the sphere come in from the back.