Chapter 6 · Troubleshooting

6.1Known Limits and What Helps

Collision

Limit	What helps
Volume collision on small characters and thin parts	Volume Only and Volume + Proxy resolve the collider on a voxel grid. On a small character, or on thin parts such as fingers, straps and belt edges, the grid is coarse compared with the detail, and the cloth rests on a blurred version of the shape. Use Surface (True Geometry), the default. If you need a volume system for speed, lower the row's Voxel from automatic until the grid is fine enough for the smallest feature that matters.
Proxy decimation	A Proxy value decimates the collider: detail is traded for speed, and a decimated hand loses its fingers. Keep Proxy at 0 on hero colliders; decimate only background colliders. In Surface (True Geometry) the value is greyed: that mode always collides with the true mesh.
Open and single-sided colliders	Tick Two-sided mesh or Open mesh on the row, then use the two levers that work: more Thickness on the row and more Substeps on the Solver.
Fast body motion (cloth passing through)	The same two levers: the row's Thickness and the Solver's Substeps. Iterations do not help, because they do not evaluate collision again.
A low-polygon collider prints its facets into the cloth	Raise Mesh contact smoothing on the Solver or Mesh Smooth on the row before adding polygons to the collider.
Cloth that starts inside a body	Surface (True Geometry) does not include the deep-penetration recovery of the volume systems. Model the garment clear of the body at the first frame.
Colliders must be meshes	An object that cannot be converted to a mesh is not added. Convert splines and surfaces to a mesh first.

Limit

What helps

Volume collision on small characters and thin parts

Volume Only and Volume + Proxy resolve the collider on a voxel grid. On a small character, or on thin parts such as fingers, straps and belt edges, the grid is coarse compared with the detail, and the cloth rests on a blurred version of the shape. Use Surface (True Geometry), the default. If you need a volume system for speed, lower the row's Voxel from automatic until the grid is fine enough for the smallest feature that matters.

Proxy decimation

A Proxy value decimates the collider: detail is traded for speed, and a decimated hand loses its fingers. Keep Proxy at 0 on hero colliders; decimate only background colliders. In Surface (True Geometry) the value is greyed: that mode always collides with the true mesh.

Open and single-sided colliders

Tick Two-sided mesh or Open mesh on the row, then use the two levers that work: more Thickness on the row and more Substeps on the Solver.

Fast body motion (cloth passing through)

The same two levers: the row's Thickness and the Solver's Substeps. Iterations do not help, because they do not evaluate collision again.

A low-polygon collider prints its facets into the cloth

Raise Mesh contact smoothing on the Solver or Mesh Smooth on the row before adding polygons to the collider.

Cloth that starts inside a body

Surface (True Geometry) does not include the deep-penetration recovery of the volume systems. Model the garment clear of the body at the first frame.

Colliders must be meshes

An object that cannot be converted to a mesh is not added. Convert splines and surfaces to a mesh first.

Self collision and layers

Limit	What helps
Cloth cutting through itself in hard folds	Self collision prevents; it does not prove. In this order: make sure Edge-edge is on; use Exclusion Mesh ring, so hems and creases folding onto the cloth beside them are seen; raise Query diameter so contacts are found earlier; raise Relaxation passes. If it still shows, set Mode to Advanced and raise Collision substeps (4, then 8): fast folds and twists are where it helps most.
The two sides of a thin garment pass through each other	Use Exclusion Mesh ring. Under it, where a garment is thinner at rest than about twice the thickness, its two layers are held at a share of their gap at rest; under Rest distance they ignore each other. Layers modelled lying on each other (closer than a tenth of that distance) are not held: leave a small gap between them in the model.
Heavy crush of many layers	When a whole outfit is compressed (a character sitting, a fall), every layer touches every other. Raise Relaxation passes and turn on Layer ordering so the inner layers hold and the outer ones give way.
Layer ordering does nothing	The check box is off, or every garment is on the same layer. Give the inner garment a lower layer number in the garment list, and raise hold strength if the order does not hold.
The garment looks inflated	Self Collision Thickness or Query diameter is too large. Thickness is a radius: layers settle about twice that distance apart.
Self friction holds less than expected in a fast crush	Grip never exceeds what the contact is pressed with. That is correct; raise hold strength if layers must stay put.

Limit

What helps

Cloth cutting through itself in hard folds

Self collision prevents; it does not prove. In this order: make sure Edge-edge is on; use Exclusion Mesh ring, so hems and creases folding onto the cloth beside them are seen; raise Query diameter so contacts are found earlier; raise Relaxation passes. If it still shows, set Mode to Advanced and raise Collision substeps (4, then 8): fast folds and twists are where it helps most.

The two sides of a thin garment pass through each other

Use Exclusion Mesh ring. Under it, where a garment is thinner at rest than about twice the thickness, its two layers are held at a share of their gap at rest; under Rest distance they ignore each other. Layers modelled lying on each other (closer than a tenth of that distance) are not held: leave a small gap between them in the model.

Heavy crush of many layers

When a whole outfit is compressed (a character sitting, a fall), every layer touches every other. Raise Relaxation passes and turn on Layer ordering so the inner layers hold and the outer ones give way.

Layer ordering does nothing

The check box is off, or every garment is on the same layer. Give the inner garment a lower layer number in the garment list, and raise hold strength if the order does not hold.

The garment looks inflated

Self Collision Thickness or Query diameter is too large. Thickness is a radius: layers settle about twice that distance apart.

Self friction holds less than expected in a fast crush

Grip never exceeds what the contact is pressed with. That is correct; raise hold strength if layers must stay put.

Seams and pins

Limit	What helps
A stitch target on another Solver	Stitches work only inside one Solver group. Instance one Solver across both garments, or use a Pin to follow a garment that has its own Solver.
A seam opens between stitch points	Sparse paint. Paint more of the seam line; the solver holds exactly the points you painted.
Stitch lines are not visible	They are drawn only while the Stitch panel is open, and only after the simulation has been built.
A pin or stitch channel is on another object	The painted channel must be on the same stack as the modifier that reads it.
Jitter near a pinned region, worst in slow motion	Pinned points inside a collider are held by the pin and pushed out by the collision on every step. Move the pinned points clear of the surface at the first frame, or paint them lighter so they form a soft pin.
Stitch set-up time on dense garments	Stitches are paired when the simulation is built, by searching every painted point against the target garment. Paint the seam, not the whole garment, and tune before you raise the density.
A Preserve on frames 3ds Max never showed	After a jump ahead on the timeline, a Tnpix Preserve has no animation for the frames in between and blends it from the nearest frames it was shown; its status line names those frames. Play from the first frame (Real Time off), or record a Tnpix Cache, and every frame is exact.
Cloth passes through the edge of a preserved region	Self collision leaves out every triangle and edge touching a point painted 1 on a Tnpix Preserve. Keep the region's hard edge where no other cloth has to rest on it, or give it a soft edge (paint below 1), whose points still collide.
A pinned point moves under a painted Soft Body or Volume	A Tnpix Soft Body or a Tnpix Volume with a Channel above a Tnpix Pin or a Tnpix Preserve lets go of the points it paints. Put the Pin above it, or paint its region off the points that must hold.
A garment of a shared Solver is a little stiffer than alone	A Tnpix Solver gives its cloth one unit of mass over all its points, so each of two equal garments in one Solver group weighs half of what it weighs on a Solver of its own, and its fabric acts slightly stiffer (a free fall is the same). Pins and a Preserve follow their Weight on either. Simulate a garment on a Solver of its own when it must match its solo result exactly.

Limit

What helps

A stitch target on another Solver

Stitches work only inside one Solver group. Instance one Solver across both garments, or use a Pin to follow a garment that has its own Solver.

A seam opens between stitch points

Sparse paint. Paint more of the seam line; the solver holds exactly the points you painted.

Stitch lines are not visible

They are drawn only while the Stitch panel is open, and only after the simulation has been built.

A pin or stitch channel is on another object

The painted channel must be on the same stack as the modifier that reads it.

Jitter near a pinned region, worst in slow motion

Pinned points inside a collider are held by the pin and pushed out by the collision on every step. Move the pinned points clear of the surface at the first frame, or paint them lighter so they form a soft pin.

Stitch set-up time on dense garments

Stitches are paired when the simulation is built, by searching every painted point against the target garment. Paint the seam, not the whole garment, and tune before you raise the density.

A Preserve on frames 3ds Max never showed

After a jump ahead on the timeline, a Tnpix Preserve has no animation for the frames in between and blends it from the nearest frames it was shown; its status line names those frames. Play from the first frame (Real Time off), or record a Tnpix Cache, and every frame is exact.

Cloth passes through the edge of a preserved region

Self collision leaves out every triangle and edge touching a point painted 1 on a Tnpix Preserve. Keep the region's hard edge where no other cloth has to rest on it, or give it a soft edge (paint below 1), whose points still collide.

A pinned point moves under a painted Soft Body or Volume

A Tnpix Soft Body or a Tnpix Volume with a Channel above a Tnpix Pin or a Tnpix Preserve lets go of the points it paints. Put the Pin above it, or paint its region off the points that must hold.

A garment of a shared Solver is a little stiffer than alone

A Tnpix Solver gives its cloth one unit of mass over all its points, so each of two equal garments in one Solver group weighs half of what it weighs on a Solver of its own, and its fabric acts slightly stiffer (a free fall is the same). Pins and a Preserve follow their Weight on either. Simulate a garment on a Solver of its own when it must match its solo result exactly.

Materials

Limit	What helps
Not every material value acts per region	See Which values act per region under Tnpix Material Standard. Relative Damp and the damping ratios act on the whole garment.
Two Advanced materials without a channel on one garment	Only the one created last acts. Bind the other to a channel, or remove it.
Fabric Curve makes no visible difference	The fabric's soft range is still too stiff to give. Its stiffness is the Stretch Stiffness divided by Lock stiffness, so raise Lock stiffness (500 or more on the stock fabric) or lower the Stretch Stiffness. A fabric that never stretches to its lock point shows only the soft range.
The × Multiplier does not switch to a higher number	Stretch Stiffness times Multiplier would pass 1e+10, so the change is refused and the box keeps its value; the line under the Stretch rows gives the product. Lower the Stiffness first, then pick the higher Multiplier.
Two garments on one Solver share one fabric	Their channels share a name, or their Standard materials have no channel, so the Solver group runs on one set of whole-garment values. Bind each garment's material to its own channel, painted over that garment, each with its own name; an Advanced material without a channel covers only its own garment.

Limit

What helps

Not every material value acts per region

See Which values act per region under Tnpix Material Standard. Relative Damp and the damping ratios act on the whole garment.

Two Advanced materials without a channel on one garment

Only the one created last acts. Bind the other to a channel, or remove it.

Fabric Curve makes no visible difference

The fabric's soft range is still too stiff to give. Its stiffness is the Stretch Stiffness divided by Lock stiffness, so raise Lock stiffness (500 or more on the stock fabric) or lower the Stretch Stiffness. A fabric that never stretches to its lock point shows only the soft range.

The × Multiplier does not switch to a higher number

Stretch Stiffness times Multiplier would pass 1e+10, so the change is refused and the box keeps its value; the line under the Stretch rows gives the product. Lower the Stiffness first, then pick the higher Multiplier.

Two garments on one Solver share one fabric

Their channels share a name, or their Standard materials have no channel, so the Solver group runs on one set of whole-garment values. Bind each garment's material to its own channel, painted over that garment, each with its own name; an Advanced material without a channel covers only its own garment.

Scene and set-up

Limit	What helps
Violent first frames	A garment that starts intersecting a collider, or far from its rest shape, is thrown on the first frames. Model it clear of the body and let Substeps calm the start.
Very dense meshes	Time grows with the vertex count, the substeps and the iterations; video memory grows with the vertex count and the number of garments. Simulate at the density the shot needs and add render detail above the Solver.
The Tear threshold changes with Substeps	The threshold is compared with a force that depends on Substeps and Iterations. The Tear status line names the pair it was typed at; set it again at the new pair.
Labels that name inches	They describe an inch scene. Values follow the scene's system unit; see Units and Scale in Chapter 2.

Limit

What helps

Violent first frames

A garment that starts intersecting a collider, or far from its rest shape, is thrown on the first frames. Model it clear of the body and let Substeps calm the start.

Very dense meshes

Time grows with the vertex count, the substeps and the iterations; video memory grows with the vertex count and the number of garments. Simulate at the density the shot needs and add render detail above the Solver.

The Tear threshold changes with Substeps

The threshold is compared with a force that depends on Substeps and Iterations. The Tear status line names the pair it was typed at; set it again at the new pair.

Labels that name inches

They describe an inch scene. Values follow the scene's system unit; see Units and Scale in Chapter 2.

Threads

Limit	What helps
Threads do not collide with each other	Each thread collides with its own cloth, the colliders and the other objects of its Solver, never with another thread. Clump bunches them into strands where that matters.
A cloth that plays from a Tnpix Cache file grows no threads	The threads read the Solver's frames. Make the threads object, add a Tnpix Cache to it and save it while the cloth still simulates.
Millions of threads	Dense spacing on a long tear makes millions of tubes. Keep Viewport % low while you work (the render makes all of them), and let Thread cap thin every crack alike.
A modifier between the Solver and the Threads	The threads read the cloth from the Solver, so a modifier in between that moves points does not move them. Put Tnpix Threads directly above the Solver.

Limit

What helps

Threads do not collide with each other

Each thread collides with its own cloth, the colliders and the other objects of its Solver, never with another thread. Clump bunches them into strands where that matters.

A cloth that plays from a Tnpix Cache file grows no threads

The threads read the Solver's frames. Make the threads object, add a Tnpix Cache to it and save it while the cloth still simulates.

Millions of threads

Dense spacing on a long tear makes millions of tubes. Keep Viewport % low while you work (the render makes all of them), and let Thread cap thin every crack alike.

A modifier between the Solver and the Threads

The threads read the cloth from the Solver, so a modifier in between that moves points does not move them. Put Tnpix Threads directly above the Solver.

Soft bodies (experimental)

Limit	What helps
An open mesh gets no flesh	A soft body needs a closed mesh: every edge shared by two faces. Close the holes (a cylinder's caps on); the status line says why there is no flesh, and the object simulates as cloth.
A Solver with a soft body is slower	A Solver that holds a closed soft body runs twice its Substeps (a soft body whose own object carries an enabled Tear does not count), so a muscle squeezed hard does not jump from one folded shape to another. Lower the Resolution for coarser, faster flesh.
A soft area painted over a Pin does not move	The Soft Body is below the Pin or the Preserve, or has no Channel. Put a Soft Body with a Channel above them: its painted points are let go. With Keep volume on, a small area on a body that is otherwise held still moves little; let go a larger area, or turn Keep volume off.
A soft body that tears has no flesh	A Tnpix Soft Body does not tear: a soft body whose own mesh its Tear splits simulates as cloth, and its status line says so. A Tear on another garment of the Solver group leaves its flesh alone.
A soft body squeezed against itself jumps	With Self Collision on, a soft body pressed hard onto itself can jump and leave a few tetrahedra inside out.
A soft body sinks through a cloth it lies on	A soft body that only lies on a pinned cloth can sink through it. Sew it to the cloth with a Tnpix Stitch.
A sliding layer buzzes	A layer that slides at Friction 0 can buzz. Keep a little Friction on the Stitch (0.3 is its default).
The muscle does not bulge	Fibres is off; or Activation is 0 with Auto tension off; or only one of Start and End is picked, and the status line says so. Pick both, or neither for a line along the object's own length.

Limit

What helps

An open mesh gets no flesh

A soft body needs a closed mesh: every edge shared by two faces. Close the holes (a cylinder's caps on); the status line says why there is no flesh, and the object simulates as cloth.

A Solver with a soft body is slower

A Solver that holds a closed soft body runs twice its Substeps (a soft body whose own object carries an enabled Tear does not count), so a muscle squeezed hard does not jump from one folded shape to another. Lower the Resolution for coarser, faster flesh.

A soft area painted over a Pin does not move

The Soft Body is below the Pin or the Preserve, or has no Channel. Put a Soft Body with a Channel above them: its painted points are let go. With Keep volume on, a small area on a body that is otherwise held still moves little; let go a larger area, or turn Keep volume off.

A soft body that tears has no flesh

A Tnpix Soft Body does not tear: a soft body whose own mesh its Tear splits simulates as cloth, and its status line says so. A Tear on another garment of the Solver group leaves its flesh alone.

A soft body squeezed against itself jumps

With Self Collision on, a soft body pressed hard onto itself can jump and leave a few tetrahedra inside out.

A soft body sinks through a cloth it lies on

A soft body that only lies on a pinned cloth can sink through it. Sew it to the cloth with a Tnpix Stitch.

A sliding layer buzzes

A layer that slides at Friction 0 can buzz. Keep a little Friction on the Stitch (0.3 is its default).

The muscle does not bulge

Fibres is off; or Activation is 0 with Auto tension off; or only one of Start and End is picked, and the status line says so. Pick both, or neither for a line along the object's own length.