Remove check for point length 0 in line material

[dmnsgn]

What's the reason for this check:

pex-shaders/shaders/pipeline/line.vert.js

Lines 43 to 45 in d3a7e5c

	if (length(aPointA) == 0.0 || length(aPointB) == 0.0) {
	gl_Position = vec4(0.0, 0.0, 0.0, 1.0);
	} else {

If that's an optimisation for empty buffers, it should be an AND operation (length(aPointA) == 0.0 && length(aPointB) == 0.0), no?

Or is it something about discontinuous paths?

Currently this won't render in pex-renderer:

const linesEntity = createEntity({
  transform: components.transform(),
  geometry: components.geometry({
    positions: [
      [0, 0, 0],
      [1, 1, 1],
    ],
  }),
  material: components.material({
    type: "line",
    baseColor: [1, 1, 1, 1],
    lineWidth: 30,
  }),
});

[vorg]

Updated PathToSegments node

const nextCell = pathCells[j + 1] || pathCells[j]; // TODO: wrong
const nextValue = pathGeometry[attributeName].slice(
   nextCell * size,
   nextCell * size + size,
);

changed to

const nextVertexIndex = pathCell[j + 1] || -1; // TODO: wrong

//if value doesn't exist depend on pre-filled 0 to insert discontinuinty 0,0,0 between paths
if (nextVertexIndex != -1) {
  const nextValue = pathGeometry[attributeName].slice(
     nextVertexIndex * size,
    nextVertexIndex * size + size,
  );
  path[attributeName].set(nextValue, size * cellIndex + size);
}

gives you answer that it is indeed "Or is it something about discontinuous paths?" as we inser 0,0,0 for discontinuities.

because how we render lines with 4 floats offset

https://github.com/pex-gl/pex-renderer/blob/v4/systems/renderer/line.js

if (entity._geometry.attributes.aVertexColor) {
      attributes.aColorA = {
        buffer: entity._geometry.attributes.aVertexColor.buffer,
        divisor: 1,
        stride: Float32Array.BYTES_PER_ELEMENT * 8,
      };
      attributes.aColorB = {
        buffer: entity._geometry.attributes.aVertexColor.buffer,
        divisor: 1,
        stride: Float32Array.BYTES_PER_ELEMENT * 8,
        offset: Float32Array.BYTES_PER_ELEMENT * 4,
      };
    }

you end up with A B C D 0 E F and 0.0 checks are agains D 0 and 0 D. So there is never two 0 to check.

As 0,0,0 is such a common use case maybe we can use different number? Can we insert NaNs or infinity there? How others do it?