Proj2 and 3

This is a project that I worked on for the Lighting Class in SCAD. The goal of the project is to build and light a model, composite it into the photo to make it look exactly the same as the object in the photo. The object that I chose is a coffee cup from SCAD cafe. Here is a detailed scan of the model and the original photo.

Top view and side view

Modeling

There are couple of challenges when I was modeling.

1. The big whole on the top

   To finish that, I first use Boolean in Maya to subtract the whole from the lid. The resulted geometry ledge loops look very unappealing. I manually fixed the meshflow afterwards.

2. The tiny hole on the top

   In order to model that on the lid, I deleted a face from the top and extruded the surrounded edges couple of times. Then I soft selected points in that area and dragged them to make them look like drilled plastic holes.

3. Round edge on the lid

   The shape of edges on the lid are in between hard and soft. So I beveled each of them and adjusted them manually after.

Lighting

To accomplish the lighting, more reference pictures are needed to calibrate the camera and figure out what the natural light looks like.

Bouncing Color

The gray box is to match the camera position in Maya. The gray ball is to get accurate bouncing color. And the chrome ball is to be used as the source of fill light in the scene. To get the tiny blue bouncing color on the left, I put a blue tube where the water bottle is.

Compositing

I rendered following layers to composite the scene

• Shadow

• AO ground contact

• AO gradation

• AO curb exaggeration

• reflection

• Beauty

In order to get the reflection, shadow look right, I model the ground according to the shape of the table in the picture. Also, I rendered another AO layer just to darken where the curbs are.

And here is how the final Nuke script looks like

Animation

Pipeline

I did the simulation in Houdini and shaded them in Maya. Here is my workflow.

1. Export model as FBX to Houdini.

2. Sim the lid.

3. Edge fracture the cup, use the lid as the collider and sim the fractures.

4. Export animation as Alembics to Maya.

5. Render as separate layers and AOVs in Maya.

6. Composite in Nuke. Add DOF and motion blur.

Here is the wire frame playblast for the simulation.

Simulation in Houdini

The sim in Houdini is a little bit tricky. Since the lid has much more weight than the paper pieces, the lid should be influencing the paper cup pieces, not vise versa. So I did the lid sim first, then used it as a collider for the cup sim. In houdini, I used vellum to do the sim. I keyed on gravity and wind in the constraint. I also played around with the friction value in the vellum solver. Here is my Houdini network.

Lighting and Compositing

Lighting and compositing in animation have more challenges than still frame. One thing need to be addressed is the reflection on the table. Since the pieces are flying everywhere, the pieces that are above the plastic bag should not have reflections. I manually rotoed them out of the frame. Another thing is the motion blur. The motion blur does not only happen in the beauty layer, but also happen on shadows and reflections.

The biggest challenge is to get rid of the noise. I rendered images in different AOVs in EXR. The noise are mostly happening in SSS indirect layer, so I used denoise in Nuke mostly in that AOV, while keeping denoise relatively low in other AOVs.In this way, I can both get rid of noises and keep the edges of the model the way I want. Here are my SSS AOVs before and after being denoised.

Conclusion

To make the project go further, I want to make the dark part on the cup more warm. In addition, the wood curves on the table in the shadow should have darker color. As for the sim, I will add more weight to the cup piece sim. Also, I want to give the paper pieces some thickness if possible.