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Chương trình ví dụ sau đây minh họa việc sinh ra ảnh bằng chiếu phối cảnh và phép chiếu song song của một đối tượng.

Program Polycon;

Uses Crt, Graph, Graph3d;

Const MaxSommet = 50;

MaxFaces = 30;

MaxAretes = 10;

IncAng = 5;

IncRho = 1;

IncEcran = 20;

Var St : Array [1..MaxSommet, 1..3] of real;

Fc : Array [1..MaxFaces,0..MaxAretes] of integer;

fff : Array [1..MaxFaces] of boolean;

O1, O2, O3 : Real;

NF : Integer;

Pointille : Boolean;

Procedure VueDeDepart;

Begin

Projection := Perspective;

Rho := 15; Theta := 0; Phi := 0;

DE := 400; Pointille := True;

End;

Procedure LectureSommets;

Begin

St[1,1] := 2; St[1,2] := 2.7; St[1,3] := -2;

St[2,1] := 2; St[2,2] := 2.7; St[2,3] := 0;

St[3,1] := 2; St[3,2] := -2.7; St[3,3] := 0;

St[4,1] := 2; St[4,2] := -2.7; St[4,3] := -2;

St[5,1] := -2; St[5,2] := -2.7; St[5,3] := -2;

St[6,1] := -2; St[6,2] := 2.7; St[6,3] := -2;

St[7,1] := -2; St[7,2] := 2.7; St[7,3] := 0;

St[8,1] := 0; St[8,2] := 1.7; St[8,3] := 2;

St[9,1] := 0; St[9,2] := -1.7; St[9,3] := 2;

St[10,1] := -2; St[10,2] := -2.7; St[10,3] := 0;

End;

Procedure LectureFaces;

Begin

NF := 9;

FC[1,0] := 4; FC[1,1] := 1; FC[1,2] := 2; FC[1,3] := 3; FC[1,4] := 4;

FC[2,0] := 4; FC[2,1] := 1; FC[2,2] := 6; FC[2,3] := 7; FC[2,4] := 2;

FC[3,0] := 3; FC[3,1] := 2; FC[3,2] := 7; FC[3,3] := 8;

FC[4,0] := 4; FC[4,1] := 2; FC[4,2] := 8; FC[4,3] := 9; FC[4,4] := 3;

FC[5,0] := 4; FC[5,1] := 1; FC[5,2] := 4; FC[5,3] := 5; FC[5,4] := 6;

FC[6,0] := 4; FC[6,1] := 7; FC[6,2] :=10; FC[6,3] := 9; FC[6,4] := 8;

FC[7,0] := 3; FC[7,1] := 3; FC[7,2] := 9; FC[7,3] :=10;

FC[8,0] := 4; FC[8,1] :=10; FC[8,2] := 5; FC[8,3] := 4; FC[8,4] := 3;

FC[9,0] := 4; FC[9,1] := 5; FC[9,2] :=10; FC[9,3] := 7; FC[9,4] := 6;

End;

ProCedure VecteurVision(St1, St2, St3:integer; Var V1, V2, V3 : rEal);

Begin

V1 := O1 - St[St1,1]; V2 := O2 - St[St1,2]; V3 := O3 - St[St1,3];

End;

Procedure VecteurNormal(St1, ST2, St3:integer; Var N1, N2, N3 : Real);

Var P1, P2, P3, Q1, Q2, Q3 : Real;

Begin

P1 := ST[St2,1] - ST[St1,1];

P2 := ST[St2,2] - ST[St1,2];

P3 := ST[St2,3] - ST[St1,3];

Q1 := ST[St3,1] - ST[St1,1];

Q2 := ST[St3,2] - ST[St1,2];

Q3 := ST[St3,3] - ST[St1,3];

N1 := P2*Q3 - Q2*P3;

N2 := P3*Q1 - P1*Q3;

N3 := P1*Q2 - Q1*P2;

End;

Function ProDuitScalaire(V1, V2, V3, N1, N2, N3: Real):Real;

Begin

ProDuitScalaire := V1*N1 + V2*N2 + V3*N3

End;

Procedure DessineObject;

Var F, St1, St2, St3, NS, No : Integer;

V1, V2, V3, N1, N2, N3 : Real;

X, Y, Z, XO, YO, ZO : Real;

Procedure DessineFace;

Var S : Integer;

Begin

NS := FC[f,0];

For S := 1 To NS Do

Begin

No := FC[F,S]; X := ST[No,1]; Y := ST[No,2]; Z := ST[No,3];

If S = 1 Then Begin

DePlaceEn(X, Y, Z);

XO := X; YO := Y; ZO := Z;

End

Else Tracevers(X, Y, Z);

End;

TraceVers(XO, YO, ZO);

End;

Begin

FillChar(FFF, Sizeof(fff), #0);

SetLineStyle(DottedLn, 0, NormWidth);

SetColor(LightRed);

For F := 1 to NF Do

Begin

St1 := Fc[F,1]; St2 := Fc[F,2]; St3 := Fc[F,3];

VecteurVision(St1, St2, St3, V1, V2, V3);

VecteurNormal(St1, St2, St3, N1, N2, N3);

If ProDuitScalaire(V1, V2, V3, N1, N2, N3) <= 0 then

Begin

If Pointille Then DessineFace;

FFF[f] := True;

End;

End;

SetLineStyle(SolidLn, 0, NormWidth);

SetColor(White);

For F := 1 to Nf Do

If Not FFF[F] Then DessineFace;

End;

Procedure CoordonneeOeil;

Begin

InitialiseProjection;

O1 := Rho * Aux7; O2 := Rho * Aux8; O3 := Rho * Aux2;

End;

Procedure Affichage;

Var S1, S2, S3, S4, S5 : String;

Begin

Cloture(0, MaxX, 0, 23); ClearViewPort;

SetTextStyle(SmallFont, HorizDir, 4);

SetColor(14);

Str(Theta:3:1, S2); Str(Phi:3:1, S3); Str(DE:3:1, S4);

IF Projection = Perspective

Then Begin

Str(Rho:3:1, S1);

OutTextXY(80, 0,'Chieu Phoi Canh: Rho = '+S1+' Theta = '+S2+

+' Phi = '+S3+' Ecran = '+S4);

End

Else OutTextXY(80,0, 'Chieu Song Song: Rho = infini Theta = '+S2+

+' Phi = '+S3+' Ecran = '+S4);

Str(MaxX, S1); Str(MaxY, S2);

OutTextXY(5, 0, S1+' x '+S2);

OutTextXY(5, 12, 'Control: ArrowKey, E, A, +, -, T, C, F-Fine');

Cloture(0, MaxX, 24, MaxY);

End;

Procedure Commandes;

Const RhoPara = 1e20;

Var RhoPersp, DEPersp, DEPara : Real;

Ch : Char;

Begin

VueDeDepart;

DEPara := 30;

CoorDonneeOeil;

DessineObject;

Affichage;

RePeat

Ch := UpCase(Readkey);

IF Ch = #0 Then Ch := UpCase(Readkey);

If Ord(Ch) In [72,80,75,77,69,65,43,45,84,67,61,95]

Then

Begin

ClearDevice;

Case Ord(Ch) Of

72 : Phi := Phi + IncAng;

80 : Phi := Phi - IncAng;

75 : Theta := Theta + IncAng;

77 : Theta := Theta - IncAng;

69 : Rho := Rho + IncRho;

65 : Rho := Rho - IncRho;

43,61 : DE := DE + IncEcran;

45,95 : DE := DE - IncEcran;

84 : Pointille := not (Pointille);

67 : If Projection = Perspective

Then Begin

RhoPersp := Rho;

DEPersp := DE;

Projection := Parallele;

Rho := RhoPara;

DE := DEPara;

End

Else Begin

DEPara := DE;

Projection := Perspective;

Rho := RhoPersp;

De := DePersp;

End;

End;

CoordonneeOeil;

DessineObject;

Affichage

End;

Until (CH = 'F') Or (ch = #13) Or (ch =#27);

EcranTexte;

End;

Begin

EcranGraphique(');

Cloture(0, MaxX, 0, MaxY);

LectureSommets;

LectureFaces;

VueDeDepart;

Commandes;

End.