Function: getMatrixImpact()

getMatrixImpact(matrix, cameraState, viewportDimensions): number

All these transformations we apply on the matrix to get it rescale the graph as we want make it very hard to get pixel-perfect distances in WebGL. This function returns a factor that properly cancels the matrix effect on lengths.

[jacomyal] To be fully honest, I can't really explain happens here... I notice that the following ratio works (i.e. it correctly compensates the matrix impact on all camera states I could try):

R = size(V) / size(M * V) / W as long as M * V is in the direction of W (ie. parallel to (Ox)). It works as well with H and a vector that transforms into something parallel to (Oy).

Also, note that we use angle and not -angle (that would seem logical, since we want to anticipate the rotation), because the image is vertically swapped in WebGL.

Parameters

• matrix: Float32Array

• cameraState: CameraState

• viewportDimensions: Dimensions

Returns

number

Defined in

sigma/src/utils/coordinates.ts:98