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120 lines
3.4 KiB
120 lines
3.4 KiB
C Copyright(C) 1999-2021 National Technology & Engineering Solutions
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C of Sandia, LLC (NTESS). Under the terms of Contract DE-NA0003525 with
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C NTESS, the U.S. Government retains certain rights in this software.
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C
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C See packages/seacas/LICENSE for details
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SUBROUTINE INVMAP (X0, Y0, X1, Y1, X2, Y2, X3, Y3, X4, Y4, SXI,
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& SETA, INSIDE)
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C***********************************************************************
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C THIS IS A TEST OF THE INVERTED MAPPING OF AN ELEMENT
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C***********************************************************************
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REAL AX, BX, CX, DX, AY, BY, CY, DY
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REAL ALPHA, BETA, GAMMA, RAD
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REAL XI, ETA, XI1, ETA1, XI2, ETA2
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LOGICAL INSIDE
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EPS = 1.E-3
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EPS2 = 1.E-10
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C GET THE A, B, C, AND D VALUES FOR X AND Y.
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AX = X1 - X0
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BX = X2 - X1
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CX = X1 - X2 + X3 -X4
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DX = X4 - X1
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AY = Y1 - Y0
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BY = Y2 - Y1
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CY = Y1 - Y2 + Y3 -Y4
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DY = Y4 - Y1
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C CALCULATE THE ALPHA, BETA, AND GAMMA VALUES.
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ALPHA = (CY * DX) - (CX * DY)
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BETA = (AX * CY) - (AY * CX) + (BY * DX) - (BX * DY)
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GAMMA = (AX * BY) - (AY * BX)
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C CALCULATE THE XI AND ETA VALUES.
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IF (ALPHA .EQ. 0.) THEN
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ETA = -GAMMA / BETA
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IF ((ETA .EQ. 0) .AND. (BX .EQ. 0)) THEN
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XI = (Y0 - Y1) / (Y2 - Y1)
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ELSE IF ((BX .EQ. -CX) .AND. (ETA .EQ. 1.)) THEN
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XI = (Y0 - Y3)/(Y4 - Y3)
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ELSE IF (BX .EQ. (-CX * ETA)) THEN
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XI = -1000.
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ELSE
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XI = (- AX - (DX * ETA)) / (BX + (CX * ETA))
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ENDIF
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ELSE
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RAD = BETA**2 - (4. * ALPHA * GAMMA)
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IF (RAD .LT. 0.) THEN
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C** NEGATIVE RADICAL PROBLEM AS IT APPEARS THAT
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C** THIS MAY OCCUR - IT JUST MEANS THAT THE POINT
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C** TRULY IS NOT IN THE ELEMENT.
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C CALL MESSAGE('** ERROR - NEGATIVE RADICAL IN INVMAP **')
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INSIDE = .FALSE.
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GOTO 100
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ENDIF
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RAD = SQRT (RAD)
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ETA1 = (- BETA + RAD) / (2. * ALPHA)
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ETA2 = (- BETA - RAD) / (2. * ALPHA)
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IF ((ABS(ETA1) .LT. EPS2) .AND. (ABS(BX) .LT. EPS2)) THEN
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XI1 = (Y0 - Y1) / (Y2 - Y1)
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ELSE IF ((BX .EQ. -CX) .AND. (ETA1 .EQ. 1.)) THEN
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XI1 = (Y0 - Y3)/(Y4 - Y3)
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ELSE IF (BX .EQ. (-CX * ETA1)) THEN
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XI1 = -1000.
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ELSE
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XI1 = (- AX - (DX * ETA1)) / (BX + (CX * ETA1))
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ENDIF
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IF ((ABS(ETA2) .LT. EPS2) .AND. (ABS(BX) .LT. EPS2)) THEN
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XI2 = (Y0 - Y1) / (Y2 - Y1)
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ELSE IF ((BX .EQ. -CX) .AND. (ETA2 .EQ. 1.)) THEN
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XI2 = (Y0 - Y3)/(Y4 - Y3)
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ELSE IF (BX .EQ. (-CX * ETA2)) THEN
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XI2 = -1000.
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ELSE
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XI2 = (- AX - (DX * ETA2)) / (BX + (CX * ETA2))
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ENDIF
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D1 = SQRT (ETA1*ETA1 + XI1*XI1)
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D2 = SQRT (ETA2*ETA2 + XI2*XI2)
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IF (D1 .LT. D2) THEN
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ETA = ETA1
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XI = XI1
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ELSE
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ETA = ETA2
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XI = XI2
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ENDIF
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END IF
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C CHECK TO SEE IF ETA AND XI ARE WITHIN THE ELEMENT
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IF (.NOT. ((ETA .LE. 1.0 + EPS) .AND.
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& (ETA .GE. 0.0 - EPS)) ) THEN
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INSIDE = .FALSE.
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GOTO 100
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ELSE IF (.NOT. ((XI .LE. 1.0 + EPS) .AND.
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& (XI .GE. 0.0 - EPS)) ) THEN
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INSIDE = .FALSE.
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GOTO 100
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ELSE
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INSIDE = .TRUE.
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ENDIF
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SXI = XI
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SETA = ETA
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100 CONTINUE
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RETURN
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END
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