TODO.txt

======================================================================================================
Easy

Add Rect (list of intervals) type
 * Return from `bounding-rectangle`
 * Accept as argument to shape constructor fuctions

Documentation
 * Add Differentiable, Smooth, deform, tessellate, etc.
 * Add "How Do I" section
 * Add notes about performance characteristics

Pict3D constructor arguments
 * Raise errors when out of range
 * Clamp to reasonable values when in range but unreasonable (e.g. subnormal)

OpenGL >= 3.2 render paths
 * Directional light
 * Point light
 * Point light shell
 * Rectangle
 * Cylinder
 * Disk

Reorder arguments in `call-with-*` functions and macros

Make dir+ and dir- take multiple arguments

Allow big-bang3d's frame-delay argument to be zero

======================================================================================================
Medium

Try doing lighting pass before solid object passes, collecting lighting information in a buffer

Face soup representation
 * Allow polygons (esp. quads)
 ? Allow non-planar polygons (requires BSP planes to have a thickness based on vertex-plane distance)
 * Fast BSP
 * Fast vertex merge (possibly based on BSP)

Replace triangle-mesh-shape with face-soup-shape to reduce vertex merge and BSP recomputation

High-level face soup shape operations
 * Combine
 * CSG intersect
 * CSG union
 * CSG subtract
 * Simplify (edge aware)

Low-level face soup shape operations
 * Goal: allow defining `deform`
 * Goal: allow defining `adaptive-tessellate`
 * Goal: allow defining `plane-vertex-normals`, `merge-vertex-normals`, `smooth-vertex-normals`
 * Replace vertices
    * Given vertex only
    * Given vertex + neighboring vertices
    * Given vertex + neighboring faces
 * Replace edges
    * Given edge only
    * Given edge + neighboring edges
    * Given edge + neighboring faces
 * Replace faces
    * Given face only
    * Given face + neighboring faces

New shape constructors
 * polygon
 * torus
 * freeze + send vertices to reside on card
 * heightmap/terrain (try a geometry shader)
 * skybox (render scene in six directions from camera, then construct a texture-mapped rect)
 * wrap with texture/skybox
 * directional light volumes (e.g. rectangle, ellipsoid, cylinder)
 * ambient light volumes

Use GL_MAP_UNSYNCHRONIZED_BIT and round-robin (should save 30% according to tests)

? Physically-based transparency (i.e. proper transmission fractions)

? Special-case transformation matrix struct for translation, uniform scaling, and rotation

? Pause big-bang3d programs to get an interactive GUI

======================================================================================================
Hard

Never produce +nan.0 internally

Automate marshaling vertex data

Add networking to pict3d/universe

Figure out a nice functional API for textures

Occlusion-based lighting
 * Screen-space ambient occlusion (paper "Scalable Ambient Obscurance")
 * Shadow mapping

pict3d%
 * Save/load pict3d% snips (waiting on Robby's redesign)
 * Make pict3d% snips display properly in algebraic stepper in student languages

Abstract the process of applying rendering passes

Find a good way to wire shaders with rendering passes

S-expression-based shader language that compiles to GLSL and can be run on the CPU for debugging

======================================================================================================
Operations

Planned operations
 * bevel
 * cap holes
 * CSG: subtract, intersect, union
 * debug: lattice (vertices, edges, or both)
 * flip faces
 * merge vertices
 * push vertices (along normal)
 * relax vertices (move toward average of neighborhood)
 * retriangulate
 * simplify
 * smooth-surfaces (Catmull-Clark or Stam-Loop? requre tessellation first?)
 * stitch cracks
 * sweeps: extrude (along axis), loft (along path), lathe (around center)

Bevel
 * size
 * number of segments or angle threshold
 * round?
 * use a given profile?

Merge vertices (see Erikson)
 * compute using connected component analysis
 * average groups of equivalent vertices as a set
 * use a hashed uniform grid

Stitch
 * close small holes
 * snap geometry on sides of cracks and gaps
 * break geometry at t-junctions

Retriangulate (simplifies soups without changing shapes, use on all new triangles after CSG ops)
 * merge coplanar polygons using connected component analysis
 * retriangulate using ear clipping

======================================================================================================
Deformations

Planned deformations
 * affect region
 * bend
 * melt
 * noise
 * spherify
 * squeeze
 * stretch
 * taper
 * twist

Affect Region: push and pull points on a mesh, with falloff
 * start point
 * end point or direction
 ? multiple start points and directions
 * ignore back facing?
 * falloff (size parameter)
 * pinch (shape parameter)
 * bubble (shape parameter)

Bend
 * center, axis
 * angle
 * upper and lower limit

Melt
 * time
 * solidity
 * axis, bottom (basically a plane)

Squeeze
 * center, axis
 * bulge amount, bulge curve
 * squeeze amount, squeeze curve
 * limits of some kind
 * amount of squeeze vs. bulge
 * volume (a percentage?)

Stretch
 * center, axis
 * stretch, amplify
 * limits of some kind

Twist
 * center, axis
 * degrees per unit
 * bias (bunched up at either end, or uniform)
 * upper and lower limits