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[diderot] Annotation of /branches/vis15/TODO
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Annotation of /branches/vis15/TODO

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Revision 1445 - (view) (download)
Original Path: trunk/TODO

1 : nseltzer 1445 THIS TODO HAS BEEN MOVED TO THE DIDEROT WIKI. PLEASE USE THAT ONE.
2 :    
3 : glk 1162 NOTE: GLK's approximate ranking of 8 most important tagged with
4 : jhr 1115 [GLK:1], [GLK:2], ...
5 :    
6 : glk 1156 ========================
7 :     SHORT TERM ============= (*needed* for streamlines & tractography)
8 :     ========================
9 : jhr 1115
10 : glk 1338 [GLK:2] Add sequence types (needed for evals & evecs)
11 : jhr 1115 syntax
12 :     types: ty '{' INT '}'
13 :     value construction: '{' e1 ',' … ',' en '}'
14 :     indexing: e '{' e '}'
15 :    
16 : glk 1338 [GLK:3] evals & evecs for symmetric tensor[2,2] and
17 : glk 1162 tensor[3,3] (requires sequences)
18 :    
19 : glk 1156 ability to emit/track/record variables into dynamically re-sized
20 : glk 1389 runtime output buffer
21 : jhr 1115
22 : glk 1442 [GLK:4] tensor fields from tensor images: Initially need at least
23 :     convolution on tensor[2,2] and tensor[3,3] (the same component-wise
24 :     convolution as for vectors).
25 : jhr 1115
26 : glk 1156 ========================
27 : glk 1162 SHORT-ISH TERM ========= (to make using Diderot less annoying to
28 :     ======================== program in, and slow to execute)
29 : jhr 1115
30 : glk 1167 Allow ".ddro" file extensions in addition to ".diderot"
31 :    
32 : glk 1204 Be able to output values of type tensor[2,2] and tensor[3,3];
33 :     (currently only scalars & vectors). Want to add some regression tests
34 :     based on this and currently can't
35 : glk 1167
36 : glk 1338 [GLK:1] Proper handling of stabilize method
37 : jhr 1115
38 : glk 1442 Convolution on general tensor images (order > 2)
39 :    
40 : glk 1162 allow "*" to represent "modulate": per-component multiplication of
41 :     vectors, and vectors only (not tensors of order 2 or higher). Once
42 :     sequences are implemented this should be removed: the operation is not
43 :     invariant WRT basis so it is not a legit vector computation.
44 :    
45 :     implicit type promotion of integers to reals where reals are
46 :     required (e.g. not exponentiation "^")
47 :    
48 : glk 1442 [Nick working on this] Save Diderot output to nrrd, instead of "mip.txt"
49 : jhr 1115 For grid of strands, save to similarly-shaped array
50 :     For list of strands, save to long 1-D (or 2-D for non-scalar output) list
51 :     For ragged things (like tractography output), will need to save both
52 :     complete list of values, as well as list of start indices and lengths
53 :     to index into complete list
54 :    
55 : glk 1442 [GLK:6] ability to declare a field so that probe positions are
56 : glk 1120 *always* "inside"; with various ways of mapping the known image values
57 :     to non-existant index locations. One possible syntax emphasizes that
58 :     there is a index mapping function that logically precedes convolution:
59 : glk 1162 F = bspln3 ⊛ (img ◦ clamp)
60 : glk 1120 F = bspln3 ⊛ (img ◦ repeat)
61 :     F = bspln3 ⊛ (img ◦ mirror)
62 :     where "◦" or "∘" is used to indicate function composition
63 : jhr 1115
64 : glk 1162 Level of differentiability in field type should be statement about how
65 :     much differentiation the program *needs*, rather than what the kernel
66 :     *provides*. The needed differentiability can be less than or equal to
67 :     the provided differentiability.
68 :    
69 : glk 1156 Use ∇⊗ etc. syntax
70 :     syntax [DONE]
71 :     typechecking
72 :     IL and codegen
73 : jhr 1115
74 : glk 1156 Add type aliases for color types
75 :     rgb = real{3}
76 :     rgba = real{4}
77 : jhr 1115
78 : glk 1389 Revisit how images are created within the language.
79 :     The "load" operator should probably go away, and its strangs
80 :     that strings are there only as a way to refer to nrrd filenames
81 :    
82 : jhr 1115 ==============================
83 : glk 1156 MEDIUM TERM ================== (*needed* for particles)
84 : jhr 1115 ==============================
85 :    
86 : glk 1442 [Lamont working on this] run-time birth of strands
87 : jhr 1115
88 :     "initially" supports lists
89 :    
90 : glk 1254 "initially" supports lists of positions output from different
91 :     initalization Diderot program (or output from the same program;
92 :     e.g. using output of iso2d.diderot for one isovalue to seed the input
93 :     to another invocation of the same program)
94 : jhr 1115
95 : glk 1442 [Lamont working on this] Communication between strands: they have to
96 :     be able to learn each other's state (at the previous iteration).
97 :     Early version of this can have the network of neighbors be completely
98 :     static (for running one strand/pixel image computations). Later
99 :     version with strands moving through the domain will require some
100 :     spatial data structure to optimize discovery of neighbors.
101 : jhr 1115
102 : glk 1156 ============================
103 :     MEDIUM-ISH TERM ============ (to make Diderot more useful/effective)
104 :     ============================
105 : jhr 1115
106 : glk 1442 [GLK:5] Want code-generation working for tensors of order three.
107 :     Order three matters for edge detection in scalar fields (to get
108 :     second derivatives of gradient magnitude), second derivatives
109 :     of vector fields (for some feature extraction), and first
110 :     derivatives of diffusion tensor fields.
111 :    
112 : glk 1156 Python/ctypes interface to run-time
113 : jhr 1115
114 : glk 1156 support for Python interop and GUI
115 : jhr 1115
116 : glk 1162 Allow integer exponentiation ("^2") to apply to square matrices,
117 :     to represent repeated matrix multiplication
118 :    
119 : glk 1156 Put small 1-D and 2-D fields, when reconstructed specifically by tent
120 :     and when differentiation is not needed, into faster texture buffers.
121 :     test/illust-vr.diderot is good example of program that uses multiple
122 :     such 1-D fields basically as lookup-table-based function evaluation
123 :    
124 :     extend norm (|exp|) to all tensor types [DONE for vectors and matrices]
125 :    
126 :     determinant ("det") for tensor[3,3]
127 :    
128 : jhr 1115 add ":" for tensor dot product (contracts out two indices
129 :     instead of one like •), valid for all pairs of tensors with
130 :     at least two indices
131 :    
132 : glk 1156 test/uninit.diderot:
133 :     documents need for better compiler error messages when output variables
134 :     are not initialized; the current messages are very cryptic
135 : jhr 1115
136 :     want: warnings when "D" (reserved for differentiation) is declared as
137 :     a variable name (get confusing error messages now)
138 :    
139 : glk 1156 ==============================
140 :     LONG TERM ==================== (make Diderot more interesting/attractive from
141 :     ============================== a research standpoint)
142 : jhr 1115
143 : glk 1156 IL support for higher-order tensor values (matrices, etc).
144 :     tensor construction [DONE]
145 :     tensor indexing [DONE]
146 :     tensor slicing
147 : jhr 1115
148 : glk 1156 Better handling of variables that determines the scope of a variable
149 :     based on its actual use, instead of where the user defined it. So,
150 :     for example, we should lift strand-invariant variables to global
151 :     scope. Also prune out useless variables, which should include field
152 :     variables after the translation to mid-il.
153 :    
154 :     test/vr-kcomp2.diderot: Add support for code like
155 :     (F1 if x else F2)@pos
156 :     This will require duplication of the continuation of the conditional
157 :     (but we should only duplicate over the live-range of the result of the
158 :     conditional.
159 :    
160 : glk 1338 [GLK:7] Want: non-trivial field expressions & functions.
161 : glk 1162 scalar fields from scalar fields F and G:
162 :     field#0(2)[] X = (sin(F) + 1.0)/2;
163 :     field#0(2)[] X = F*G;
164 :     scalar field of vector field magnitude:
165 : glk 1156 image(2)[2] Vimg = load(...);
166 :     field#0(2)[] Vlen = |Vimg ⊛ bspln3|;
167 : glk 1162 field of normalized vectors (for LIC and vector field feature extraction)
168 :     field#2(2)[2] F = ...
169 :     field#0(2)[2] V = normalize(F);
170 :     scalar field of gradient magnitude (for edge detection))
171 : glk 1156 field#2(2)[] F = Fimg ⊛ bspln3;
172 :     field#0(2)[] Gmag = |∇F|;
173 : glk 1162 scalar field of squared gradient magnitude (simpler to differentiate):
174 : glk 1156 field#2(2)[] F = Fimg ⊛ bspln3;
175 :     field#0(2)[] Gmsq = ∇F•∇F;
176 : glk 1162 There is value in having these, even if the differentiation of them is
177 :     not supported (hence the indication of "field#0" for these above)
178 : glk 1156
179 : jhr 1195 Introduce region types (syntax region(d), where d is the dimension of the
180 :     region. One useful operator would be
181 :     dom : field#k(d)[s] -> region(d)
182 :     Then the inside test could be written as
183 :     pos ∈ dom(F)
184 :     We could further extend this approach to allow geometric definitions of
185 :     regions. It might also be useful to do inside tests in world space,
186 :     instead of image space.
187 :    
188 : glk 1162 co- vs contra- index distinction
189 : glk 1156
190 : glk 1162 Permit field composition:
191 : glk 1156 field#2(3)[3] warp = bspln3 ⊛ warpData;
192 :     field#2(3)[] F = bspln3 ⊛ img;
193 :     field#2(3)[] Fwarp = F ◦ warp;
194 : glk 1162 So Fwarp(x) = F(warp(X)). Chain rule can be used for differentation.
195 :     This will be instrumental for expressing non-rigid registration
196 :     methods (but those will require co-vs-contra index distinction)
197 : glk 1156
198 : glk 1155 Allow the convolution to be specified either as a single 1D kernel
199 :     (as we have it now):
200 :     field#2(3)[] F = bspln3 ⊛ img;
201 :     or, as a tensor product of kernels, one for each axis, e.g.
202 :     field#0(3)[] F = (bspln3 ⊗ bspln3 ⊗ tent) ⊛ img;
203 : glk 1212 This is especially important for things like time-varying fields
204 :     and the use of scale-space in field visualization: one axis of the
205 :     must be convolved with a different kernel during probing.
206 :     What is very unclear is how, in such cases, we should notate the
207 :     gradient, when we only want to differentiate with respect to some
208 :     subset of the axes. One ambitious idea would be:
209 : glk 1162 field#0(3)[] Ft = (bspln3 ⊗ bspln3 ⊗ tent) ⊛ img; // 2D time-varying field
210 : glk 1204 field#0(2)[] F = lambda([x,y], Ft([x,y,42.0])) // restriction to time=42.0
211 :     vec2 grad = ∇F([x,y]); // 2D gradient
212 : glk 1155
213 : glk 1162 representation of tensor symmetry
214 : jhr 1115 (have to identify the group of index permutations that are symmetries)
215 :    
216 :     dot works on all tensors
217 :    
218 :     outer works on all tensors
219 :    
220 : glk 1204 Help for debugging Diderot programs: need to be able to uniquely
221 :     identify strands, and for particular strands that are known to behave
222 :     badly, do something like printf or other logging of their computations
223 :     and updates.
224 :    
225 :     Permit writing dimensionally general code: Have some statement of the
226 :     dimension of the world "W" (or have it be learned from one particular
227 :     field of interest), and then able to write "vec" instead of
228 :     "vec2/vec3", and perhaps "tensor[W,W]" instead of
229 :     "tensor[2,2]/tensor[3,3]"
230 :    
231 :     Traits: all things things that have boilerplate code (especially
232 :     volume rendering) should be expressed in terms of the unique
233 :     computational core. Different kinds of streamline/tractography
234 :     computation will be another example, as well as particle systems.
235 :    
236 : jhr 1115 Einstein summation notation
237 :    
238 :     "tensor comprehension" (like list comprehension)
239 :    
240 : glk 1204 Fields coming from different sources of data:
241 :     * triangular or tetrahedral meshes over 2D or 3D domains (of the
242 :     source produced by finite-element codes; these will come with their
243 :     own specialized kinds of reconstruction kernels, called "basis
244 :     functions" in this context)
245 :     * Large point clouds, with some radial basis function around each point,
246 :     which will be tuned by parameters of the point (at least one parameter
247 :     giving some notion of radius)
248 :    
249 : jhr 1115 ======================
250 :     BUGS =================
251 :     ======================
252 :    
253 :     test/zslice2.diderot:
254 :     // HEY (bug) bspln5 leads to problems ...
255 :     // uncaught exception Size [size]
256 :     // raised at c-target/c-target.sml:47.15-47.19
257 :     //field#4(3)[] F = img ⊛ bspln5;
258 : glk 1336

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