# Pop Networks > MUST READ before building or editing POP networks, particle systems, GPU point/geometry work, glslPOP compute, or converting SOP chains to POPs in TouchDesigner 2025+. - Skill: `dylanroscover/pop-networks` (Agent Skill) - Install (CLI): `npx skillmds@latest add dylanroscover/pop-networks` - Raw SKILL.md: https://api.skillmd.com/api/skills/dylanroscover/pop-networks/raw - Safety review: pending - Works with: Claude Code, Claude.ai, OpenAI Codex - Category: Coding & Dev Tools - Author: dylanroscover (https://skillmd.com/u/dylanroscover) - Updated: 2026-09-17 - Page: https://skillmd.com/skills/dylanroscover/pop-networks --- # POP Networks Build GPU-resident point and geometry systems with TouchDesigner POPs. POPs are the 2025+ point-operator family: geometry attributes live on the GPU, many operations run in parallel, and the right chain can replace CPU-heavy SOP or particle workflows. Use this skill with `/create-operator`, `/visual-aesthetics`, `performance.md`, `network-layout.md`, and `td-python.md`. POP correctness is not just a clean network: it is a rendered frame, readable layout, bounded performance, and no operator errors. ## POPs vs SOPs Use POPs when the work is point-heavy, particle-heavy, or naturally parallel: - Many points, particles, trails, instancing templates, or live geometry streams. - GPU-side displacement, filtering, attributes, neighborhood queries, texture lookups, or simulation loops. - Geometry that needs to stay GPU-resident for rendering, instancing, GLSL, or TOP/MAT interop. - SOP chains whose main cost is moving or filtering lots of points every frame. Keep SOPs when they are the honest tool: - Booleans, UV unwrap, small static meshes, precise CPU geometry tools, or legacy SOP-only workflows. - Tiny one-off static shapes where a SOP is clearer and has no measurable cost. - Any workflow that needs a mature CPU operator with no POP equivalent. Prefer POPs for dynamic scale, not as a religion. Start from the user's goal, expected point count, and render path, then choose the family that keeps the system understandable and fast. ## Core Vocabulary Generators create points or geometry: - `gridPOP`, `boxPOP`, `spherePOP`, `torusPOP`, `tubePOP`, `circlePOP`, `linePOP`, `rectanglePOP`. - `randomPOP`, `sprinklePOP`, `pointgeneratorPOP`, `patternPOP`, `curvePOP`. - `particlePOP` creates and manages built-in particles over time. - `sourcePOP` is common in feedback-style particle systems. Filters and topology ops reshape or route data: - `transformPOP`, `mathPOP`, `mathmixPOP`, `mathcombinePOP`, `normalizePOP`, `limitPOP`, `rerangePOP`, `quantizePOP`, `trigPOP`. - `noisePOP` for built-in noise displacement or attribute generation. - `attributePOP`, `attributecombinePOP`, `attributeconvertPOP`, `normalPOP`. - `mergePOP`, `switchPOP`, `selectPOP`, `deletePOP`, `groupPOP`, `sortPOP`, `copyPOP`, `blendPOP`, `nullPOP`. - `primitivePOP`, `convertPOP`, `extrudePOP`, `subdividePOP`, `facetPOP`, `polygonizePOP`. Spatial and simulation ops add interaction: - `neighborPOP` adds `Nebr` and `NumNebrs` for GPU spatial-neighbor logic. - `proximityPOP`, `rayPOP`, `fieldPOP`, `lookuptexturePOP`, `lookupchannelPOP`. - `feedbackPOP` loops frame-to-frame. Input 0 is the reset geometry; loopback from the output is automatic. - `cachePOP`, `cacheblendPOP`, `cacheselectPOP`, `trailPOP`, `linemetricsPOP`, `skinPOP`. - Forces for particle workflows should start conservative: gravity around `0.1-0.2`, damping around `0.98`. GLSL POPs are for work the built-ins cannot express cleanly: - `glslPOP`: default custom compute operator for one attribute class, multi-pass support. - `glsladvancedPOP`: use only when you need multi-class read/write, `I[]` index-buffer access, extra outputs, or custom output counts. - `glslcopyPOP`: copy source geometry many times with custom per-copy transforms. - `glslcreatePOP`, `glslselectPOP` for create/select patterns around GLSL outputs. Converters bridge POPs to other families: - Into POPs: `soptoPOP`, `choptoPOP`, `dattoPOP`, `toptoPOP`, file/Alembic/point-file POPs. - Out of POPs: `poptoCHOP`, `poptoDAT`, `glslmultiTOP`, MAT attribute pages. - `lookuptexturePOP` samples TOPs from POP attributes. Set lookup attrs deliberately. ## geometryCOMP Setup Ritual For renderable POP geometry, build inside a `geometryCOMP`: 1. Create the `geometryCOMP`. 2. Delete the auto-created torus immediately. 3. Build the POP chain left-to-right and terminate in `null_out` or another role-named `nullPOP`. 4. Set display and render flags on the output `nullPOP`. 5. Add a material that can shade the points or geometry. 6. Reference the MAT on the `geometryCOMP` with a relative path such as `./pointsprite_particles`. 7. Render through a camera, light as needed, and a Render TOP. Point rendering needs point primitives and a point-capable material: - Points alone do not render. On generators, set Connectivity to create point primitives when you intend to render points. - Use `pointspriteMAT` for particle sprites, or a MAT that can read point/vertex attributes for the intended render style. - The POP render color attribute is `Color` as `float4`, not `Cd`. `Cd` is the SOP habit and will not do what you expect in POP render paths. - `constantMAT` can render point and primitive `Color` when point color application is enabled. - Filled POP surfaces may be invisible from one side under backface culling. If that is not desired, set the MAT cull face to neither. ## Attributes Reserved/common attributes to recognize: - `P` float3 position, `N` float3 normal, `T` float4 tangent, `Color` float4 RGBA, `Tex` float3 texture coordinate. - `PointScale`, `LineWidth`, `Weight`. - Particle attributes from `particlePOP`: `PartVel`, `PartId`, `PartAge`, `PartLifeSpan`, `PartDrag`, `PartMass`, `PartForce`. - Neighbor attributes from `neighborPOP`: `Nebr`, `NumNebrs`. Access components as `P.x`, `P.y`, `P.z`, `Color.r`, or with POP parameter component syntax such as `P(0)`. Use dot notation in GLSL for readability. Custom attributes must exist before downstream code writes them. Use `attributePOP` upstream or the Create Attributes sequence on the GLSL POP itself. In sequence parameters, set the block count first, then set names and types such as `attr0name` and `attr0type`. ## Particle Lifecycle For `particlePOP` and `feedbackPOP`, creation is not enough: 1. Pulse `initializepulse` to reset from the input geometry. 2. Pulse `startpulse` to begin playback. 3. Use `play` to pause or resume without resetting. 4. Reinitialize after changing attribute schema, birth/life/capacity, or any upstream reset geometry that changes the expected state. Particle capacity is a hard cap: - `pointgeneratorPOP.numpoints` is emission positions, not live particle count. - `particlePOP.birthrate` is births per second. - `particlePOP.life` is seconds each particle remains alive. - `particlePOP.maxparticles` must be at least `birthrate x life`, or particles are culled before their intended lifespan. Start with modest counts and ramp only after measuring. Never default to millions. ## GLSL POP Discipline Use built-in POPs before custom GLSL when a short POP chain is clearer. `lookuptexturePOP -> mathmixPOP` is often better than a shader for texture lookup plus arithmetic. For `glslPOP`: - Write shader code in the auto-docked `_compute` DAT. Do not point at an unrelated text DAT. - Read compile details from the docked `_info` DAT; the operator error may only say compile failed. - List every written attribute in `outputattrs`. - Create custom output attributes first with the `attr` sequence, for example `attr0name` and `attr0type`, or create them upstream with `attributePOP`. - With default `outputaccess=writeonly`, attributes listed in `outputattrs` that the shader does not write may be zeroed. Use `readwrite` when the shader must read output buffers, such as reading other points during a simulation. - Guard indexes: `if (idx >= uint(P.length())) return;`. - `TDPerlinNoise()` is not available in compute shaders. Use built-in `noisePOP`, a sampler input, or custom compute-safe noise. - Uniforms are auto-declared by TD. Do not redeclare them in the shader; a redeclared uniform can produce a "Redeclaration" compile error. - Use `vec` uniform sequence entries for runtime values. `const` sequence entries recompile the shader when they change. For `glslcopyPOP`: - Input 0 is source geometry. Input 1 is template points when copy count should follow points. - Write the point shader in the auto-docked `_ptCompute` DAT. Separate text DATs can compile while `TDCopyIndex()` stays wrong. - Delete unused `_vertCompute` and `_primCompute` docked DATs only if you are sure that build does not need them. - Core functions include `TDCopyIndex()`, `TDTemplate_P()`, `TDTemplate_AttribName()`, `TDIn_P()`, `TDInputIndex()`, and `TDUpdatePointGroups()`. For `glsladvancedPOP`: - Use it only when `glslPOP` cannot express the output class, topology, index buffer, or output-count requirements. - Allocate output buffers explicitly. Point outputs need custom max points > 0; primitive/vertex/index outputs need custom max triangles > 0. - Custom attributes need both Create Attribs and the matching output attributes parameter (`ptoutputattrs`, `primoutputattrs`, or `vertoutputattrs`). - In cache feedback patterns, use `cachePOP -> locked nullPOP` to break cook dependency loops. Refresh with the unlock-cook-lock sequence: `null.lock = False; null.cook(force=True); null.lock = True`. A `.tdxn` does not store that null's points (Embody's locked-content warning names it): after the COMP is rebuilt from its `.tdxn`, run the refresh again. ## Conversion and Extraction Use conversions deliberately because GPU -> CPU readback can stall: - `poptoCHOP` and `poptoDAT` download GPU data to CPU. Keep counts small or sample/debug only. - `poptoCHOP` channel names use `attr_component`, for example `P_0`, `P_1`, `P_2`. - `lookuptexturePOP` defaults can use world position components (`P(0)`, `P(1)`) rather than UVs. Set lookup index attrs to `Tex(0)` and `Tex(1)` when sampling by UV. - pbrMAT and phongMAT read `Tex` as a vertex attribute, not a point attribute. Use `attributeconvertPOP` with point-to-vertex conversion for `Tex`; disable conflicting built-in vertex Tex on the source if needed. - `normalPOP` should set tangents to `alwayscompute` when using pbrMAT, or PBR lighting can fail. ## Embody Workflow Gates Performance is part of the build: - Before any particle, feedback, GLSL, instancing, or large POP build, call `get_project_performance(include_hotspots=5)` and record the baseline required by `performance.md`. - Re-check after each significant step, not only at the end. - Watch GPU headroom, frame time, dropped frames, hotspot cook time, and memory. Stop on the `performance.md` thresholds. - Start particle and instance counts modestly, then ramp with evidence. Do not default to millions. Layout is part of the build: - POP chains still follow the 200-unit grid and left-to-right signal flow. - `glslPOP`, `glslcopyPOP`, and other GLSL operators dock compute/info DATs. Place every docked DAT with the docked-DAT formula from `network-layout.md`. - `execute_python` creation drops POPs at `(0, 0)` unless you position them. A `LAYOUT WARNING` is a hard stop: query layout, move the ops, move docked DATs, and verify again. - Every logical POP cluster gets an annotation enclosing its operators. Naming is part of readability: - Use `optype_name` for processing ops: `grid_points`, `noise_displace`, `glsl_sim`, `particle_emit`, `feedback_state`, `null_out`. - Name DATs by role, not type. Keep generated docked DAT names unless the operator requires them. Verification is visual and structural: - A POP render chain is verified by rendering it. Capture the Render TOP output with `capture_top` and judge the frame using `/visual-aesthetics`. - Let simulations settle before judging. Empty early frames can be lifecycle or demand issues, not final appearance. - Verify animation over time with multiple captures when the POP chain is time-dependent. - Run `get_op_errors` with `recurse=true` after creating or modifying the network. Fix errors and warnings before claiming the build works. ## Trap List - `rectanglePOP` size parameters are `sizeu` and `sizev`, not `sizex` or `sizey`. Setting `sizex`/`sizey` silently does nothing. General rule: verify live parameters with `get_parameter` before trusting type-level help or component names. - The default torus inside a new `geometryCOMP` will render if you leave it there. Delete it before building the POP chain -- this is the general geometryCOMP rule; see `/create-operator` -> "Geometry COMP: delete the default torus" for the render-flag detail. - No display/render flags on the output `nullPOP` means the render is empty. - Points without point primitives do not render. - POP render color is `Color` (`float4`), not SOP-style `Cd`. - `particlePOP` and `feedbackPOP` need `initializepulse -> startpulse -> play`. Reinitialize after attribute changes or schema changes. - `maxparticles < birthrate x life` culls particles. - Custom attributes must exist before GLSL writes them. Create them with the `attr` sequence (`attr0name`, `attr0type`) or upstream `attributePOP`. - `glslPOP` writes to the docked compute DAT. Do not redeclare auto uniforms. Use `vec` for runtime values and avoid `const` for values that should animate without recompiling. - `TDPerlinNoise()` is not available in POP compute shaders. - `normalPOP` needs tangents set to `alwayscompute` for PBR lighting. - pbrMAT reads vertex `Tex`, not point `Tex`; convert with `attributeconvertPOP`. - `mathmixPOP` and `mathcombinePOP` sequences start empty. Set `numBlocks` before setting `comb0oper`, `vec0*`, or similar sequence parameters. - `poptoCHOP` outputs channels like `P_0`, `P_1`, `P_2`, not `P.x`. - `feedbackPOP` starts empty until initialized. Cache-feedback loops need the locked-null unlock-cook-lock refresh sequence. - `copyPOP` multiplies source vertices by template count. For many copies, prefer GPU instancing or a simpler point-rendered approach. - `poptoCHOP` and `poptoDAT` read back from GPU to CPU. Use them for debugging or bounded extraction, not large live particle fields. - `lookuptexturePOP` defaults may sample by `P`, not `Tex`. Set lookup attrs explicitly. - Filled primitives may disappear from one side because of MAT culling. Adapted from Derivative's TDMCPSkills (td-pop-family), with permission. Verify build-specific behavior against docs.derivative.ca.