Trace POP

Summary

The Trace POP reads a TOP image and traces it, generating line strips around areas exceeding a certain brightness threshold. You can control the threshold using the Threshold parameter, and compare it with the pixel value determined by the Channel menu, by default the brightness.

The line strips can be triangulated into triangular surfaces, ore left in its basic (fastest but least useful) form as 2-point lines.

The resolution of the resulting line strips or triangle meshes can be reduced using the Resolution Multiplier parameter.

You can smooth the line strips using the Smooth Edge Distance parameter which is similar to the snoothing in the Line Smooth POP.

The Extend menu determines is the line strips continue around the border or are separates as open line strips.

The Winding will make outer line strips that are counter-clockwise, and line strips enclosed in them to be clockwise.

The output is -.5 to .5 in X (P(0)) but it can be re-ranged with the ReRange P parameters.

You may need to adjust the Max Num Line Strips parameter or the Max Num Verts parameter (since these numbers need to be pre-determined for the GPU to avoid overflows).

tracePOP_Class

Parameters - Trace Page

Input Attribute Scope inputattrscope - When using a POP with dimension 2 as an input, the attribute scope to sample.

Use Position Attribute posattrib - When using a POP with dimension 2 as an input, whether to use the P attribute to position the threshold lines.

TOP top - TOP to sample.

Channel channel - ⊞ - When using a TOP input, the color channel to sample.

Luminance luminance -

Red red -

Green green -

Blue blue -

Alpha alpha -

RGB Average rgbaverage -

RGBA Average average -

RGB Maximum rgbmax -

RGBA Maximum max -

Resolution Multiplier resmult - Resolution multiplier to apply to the input.

Threshold threshold - The threshold value to determine what is inside the surface and what is outside (empty).

Inside inside - ⊞ - Whether values above the threshold or below or equal the threshold are considered inside. For contours, that determines the direction of the segments.

Below/Equal to Threshold below -

Above Threshold above -

Extend extend - ⊞ - How to sample outside the boundaries, which is needed to determine what happens at the boundaries. Zero returns 0, Hold returns the boundary value.

Hold hold -

Zero zero -

Output twodimensions - ⊞ - Whether to output a contour, lines or line strips, or a surface made of triangles.

Contour (Lines) contour -

Contour (Line Strips) contourls -

Surface (Triangles) surface -

Unique Points uniquepoints - When outputting Lines, whether the points are shared between the lines or unique to each line.

Winding winding - ⊞ - When outputting line strips, by default the closed line strips will be oriented counterclockwise around surfaces, and clockwise around holes. Counterclockwise reverses the line strips around holes so they're counterclockwise as well.

Natural natural -

Counter ClockWise ccw -

Smooth Edge Distance smooth - ⊞ - When outputting line strips, smoothes the line strips, averaging neighboring points positions, using the distance value.

Smooth Edge Distance smooth -

Smooth Edge Distance filterdist -

ReRange P rerangep - Whether to ReRange P.

Map to Low tolow - ⊞ - The low value of the new range in X and Y.

Map to Low tolow0 -

Map to Low tolow1 -

Map to High tohigh - ⊞ - The high value of the new range in X d Y.

Map to High tohigh0 -

Map to High tohigh1 -

Normal normal - ⊞ - Whether to output a Normal (N) attribute.

None none -

Point point -

Primitive prim -

Normal Direction normaldirection - ⊞ - Chooses the normal direction when outputting normals.

Default default -

+Z z -

Texture Coordinates texture - Whether to output a point Texture Coordinates attribute (Tex)

Fraction of Max Allocation allocfract - This POP doesn't know in advance how much GPU memory it will need, but except in rare cases (very high amount of detail, a lot of variation in neighboring pixels in the source) it doesn't need the maximum allocation. This allows to save GPU memory. If points and primitives are missing or the info popup shows the max numbers are reached, it means the fraction is too low.

Max Num Line Strips setmaxnumls - ⊞ - Optional toggle, saves some GPU memory when set correctly.

Max Num Line Strips setmaxnumls -

Max Num Line Strips maxnumls -

Max Num Verts per Line Strip setmaxnumvertsperls - ⊞ - Optional toggle, can help prevent the GPU being stuck in infinite loops, doesn't save memory.

Max Num Verts per Line Strip setmaxnumvertsperls -

Max Num Verts per Line Strip maxnumvertsperls -

Copy Topology Info Back to CPU cpureadback - Copy back the point count info and topology info held on the GPU back to CPU. Causes a stall for discrete GPUs.

Parameters - Common Page

Bypass bypass - Pass through the first input to the output unchanged.

Free Extra GPU Memory freeextragpumem - Free memory that has accumulated when output memory has grown and shrunk.

Delete Input Attributes delinputattrs - Only output which attributes you specify in this POP - helps isolate attributes into a separate branch.

Operator Inputs

Input 0: -

Info CHOP Channels

Extra Information for the Trace POP can be accessed via an Info CHOP.

Common POP Info Channels

Common Operator Info Channels

total_cooks - Number of times the operator has cooked since the process started.

cook_time - Duration of the last cook in milliseconds.

cook_frame - Frame number when this operator was last cooked relative to the component timeline.

cook_abs_frame - Frame number when this operator was last cooked relative to the absolute time.

cook_start_time - Time in milliseconds at which the operator started cooking in the frame it was cooked.

cook_end_time - Time in milliseconds at which the operator finished cooking in the frame it was cooked.

cooked_this_frame - 1 if operator was cooked this frame.

warnings - Number of warnings in this operator if any.

errors - Number of errors in this operator if any.

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