A collection of shaders and tools for creating and rendering cartoon meshes.
The shading model is a collection of techniques (see References) combined with my own experimental techniques for easier artist-driven detail work.
Rough idea: This shader performs flat three tone (spec, diffuse, shadow) lighting based on vertex colors, and adds silhouette and hand-painted crease edges to the geometry. (Crease is legacy terminology that I need to change). It makes several attempts to maintain a more 2D artstyle, e.g. by having edge widths uniform in screen space and changing how the light models behaves to make things a little less realistic, and hopefully overcome some of the weaknesses of traditional NPR methods.
tl;dr - make 3D thing more 2D thing, hopefully.
- Maya 2018+ with the GLSL Shader plugin enabled
- Disable "Consolidate World" in the viewport. Geometry shader(s) currently cannot handle Maya's attempt at optimizing geometry caches.
(... I'll clean this up once it's more fixed)
Color information comes from vertex painting the RGB channels of the crease colorset. Creases and silhouettes inherit the
Three LOD levels (0-2) are supported, using UE4-like screen coverage to calculate whether or not the model is in a given LOD. Each crease edge painted on the model can be assigned a specific LOD and will only be visible within that LOD.
By default, LOD0 is when the model's bounding box fills more than 66% of the screen, LOD2 when it covers 33% to 66%, and LOD2 when it covers less than 33%.
LOD bounding box is currently shared by all models that use the same material instance, so it's not particularly useful when compositing a full scene with shared materials within Maya. Bounding boxes are not shared in the actual game engine(s) so it becomes useful when prepping an individual model.
Each painted crease can be given a specific set number that corresponds with additional uniform metadata about how creases in that set should be rendered - allowing for different rendering methods of groups of creases on the same mesh.
- Light cookies / decal for texture-driven specular reflections.
- Experiment with triplanar texturing for edges
Experiment with migrating GS code into a PN-AEN tessellation pipeline instead to reduce the amount of overhead calculations (performing edge detection prior to tessellation, rather than after on a larger number of edges). UE4 supports providing adjacency information to the tessellation pipeline so it should be safe to utilize Maya's GLSL_PNAEN9 to its fullest.UE4-style LODs using screen space sizes of mesh bounding boxes instead of position distances- Resolve remaining z-order issues from edges to eliminate any uniform adjustments to make it "just right" per mesh.
- Transparency - uniform and texture-based using whatever the alpha channel is in the texture. Nightmare for Maya - may avoid and just deal with in-engine solutions
- Sharp texture mapping and decals
Better draw modes for Maya to avoid hiding vertex/edge selections behind geometry- Silhouette control painting (variable widths, rejection)
- Better shadows (low priority though - this will end up being very engine-specific)
Bærentzen, J. A., Munk-Lund, S., Gjøl, M., & Larsen, B. D. (2008). Two Methods for Antialiased Wireframe Drawing with Hidden Line Removal. Proceedings of the Spring Conference in Computer Graphics
Boubekeur, T., & Alexa, M. (2008). Phong Tessellation. ACM Trans. Graph., 27, 141:1-141:5.
DesLauriers, M. (2015). Drawing Lines is Hard. Retrieved from https://mattdesl.svbtle.com/drawing-lines-is-hard
Hajagos, B., Szécsi, L., & Csébfalvi, B. (2013). Fast silhouette and crease edge synthesis with geometry shaders. Budapest University of Technology and Economics
Rideout, P. (2010). Antialiased Cel Shading. Retrieved from https://prideout.net/blog/old/blog/index.html@p=22.html