Gnomon DVD: Paint Effects: Polygons & Dynamics

Ethan talks about optimizing large poly count scenes generated by paint effects, and combining dynamics with paint effects.

The first tip would be to make things closer to camera the ‘hero’ objects with extreme complexity, while cheating on the rest. Ethan mentions that nurbs surfaces are more friendly to paint on than polygons due to overlapping UVs of polygons. Also, rendering is an issue – subdivisions work well with displacement maps and such, so we need to decide whether to convert polygons to subdivisions or nurbs for the high level of detail.

Mid-ground objects requires some edge softness to be nice. Especially at the ground level, root fade is useful, but it is only available as a paint effects object. When converted to polygons, we can reduce what we don’t need, like those branches in the distance. We could smooth only the trunk etc. Also as mentioned before, leaf forward twist is our friend for certain moving shots. Another interesting technique is to use 2D leaves with 3D trunks or such hybrids.

Ethan did a test with rendering. Paint effects objects render faster at close-ups, while polygons are faster at a distance. Paint effects scenes are also very RAM heavy, which means rendering would need to take place in a batch command for faster results. This means we should decide what needs to be converted to polygons for rendering for load balancing.

For depth, paint effects will only work when the camera depth type is set to closer visible depth.

One technique to make a 3D paint effects object into 2D while retaining the same look is to put the render into photoshop and make a work path around the contours, import the path into Maya, make into a 2D plane and project the rendered texture.

For rendering, we always need to put our paint effects into one render layer, and polygons into another. We then enable z-depth in the render, setting up our near and far clip plane beforehand. For environmental fog, paint effects fog works quite well in a complex scene just by painting on the ground plane.

Paint effects instancing is a good way to reduce the amount of calculations in a scene, which is suitable for populating a jungle ground. Do this using particles instancer. For cheap wind movement, use a soft body lattice with original soft + goals + volume axis field. The field can be a torus so the middle part (e.g trunk) moves lesser. Edit > keys > Bake simulation to commit the animation.

Refining a polygon converted from paint effects is not too difficult. First thing is to separate the mesh, hide what is not needed, and refine the level of detail by tweaking the width scale graph (so that overlapping details are removed). Make a smooth proxy to preview and edit the form. Delete overlapping meshes that does not describe the form much, move the meshes around to cover holes or use sculpt polygon tool to do that. If we need a branch at certain locations, we can extrude it ourselves, then use wire deformer for motion. Don’t forget that blend shapes works too!

We can create displacement maps with zbrush so that we have a very high level of detail, for extreme close-ups and such. We export the mesh as an obj, put into zbrush, sculpt, then export the displacement and normal maps (in low subdiv) and the obj in low, middle and high subdiv level. This is because if we need dynamics, we can use the low one with displacement map. Mid level offers fast performance and renders with bump/normal.

Paint effects can also add details to objects, like tearing on a couch. It’s a detail machine!

Ethan also shows his old project where he makes some curves in illustrator and use the copy and paste settings in paint effects to apply it on them. If the paths are tight, decrease global scale and use normal to fix direction. This is awesome for motion graphics in my opinion!

Paint effects alone does not work with raytracing, and depth map shadow “mid dist dmap” and “use dmap auto focus” must be turned off on the lights. Also adjust the illumination settings.

Paint effects polygons are skeleton to emit particles from. We can have fire swirls than emit sparkly particles that are controlled by fields to get quite realistic stuff.

Amazing technology, are you geared up to use it?


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