Trapezoids

Modeling volume shape

Rotations

Display

Interactions with ACD code

Status

pDx2

pDy1

X

Y

pDx1

xDiff

h

pAlp1

(cx1, cy1)

(cx2, cy2)

top (X2)

bottom (X1)

Bold black <--> G4Trap parameter

Bold magenta <--> gdd parameter

pAlp1 = atan(xDiff/h)

pDx1 = ½ bottom edge

pDx2 = ½ top edge

pDy1 = ½ h

xDiff = cx2 – cx1

pDz = ½ thickness

Trapezoidal Prism Parametrized

Z

Rotations

Versions of xmlGeoDbs prior to v1r46 defined side tiles so that no rotations were necessary; i.e., local coordinate system = LAT global coord.

G4 trapezoidal solids have a canonical orientation: Z is thickness, Y is height of trapezoid.

==> All trapezoidal tiles must be rotated. Easiest to just rotate all side tiles.

Rotations (2)

X

Y

Z

Local coords

LAT coords achieved by

rotating (90 + row 1 slant) about X

Tile 214

(-Y face)

For other faces, rotation about X is followed by one about Z.

This appears to be working correctly as displayed by Fred. Don't yet know about G4.

We still need a way to display geometry directly from Geant!

Acd Code & Geometry

There is no feasible automatic way for ACD code to handle all these changes, but we could do better

Auxilliary xml file in xmlGeoDbs pkg, to be read by AcdUtil

Per-subsystem version info in geometry description

In the meantime, must be careful to build releases with compatible pkg versions.

Status

Trapezoids are in geometry description and fully supported as of GR LATEST-1.3441

In Fred display

In generation of G4 geometry

In ACD code, thanks to Eric C.

but the last two are entirely untested.

2007-10-29T16:13:35