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+  ------------------------ --------------------------------- --------------------
+  [Previous](52-03.html)   [Table of Contents](index.html)   [Next](52-05.html)
+  ------------------------ --------------------------------- --------------------
+
+**LISTING 52.6 L52-6.C**
+
+    /* Rotates and moves a polygon-based object around the three axes.
+       Movement is implemented only along the Z axis currently. */
+
+    #include “polygon.h”
+
+    void RotateAndMovePObject(PObject * ObjectToMove)
+    {
+       if (--ObjectToMove->RDelayCount == 0) {   /* rotate */
+          ObjectToMove->RDelayCount = ObjectToMove->RDelayCountBase;
+          if (ObjectToMove->Rotate.RotateX != 0.0)
+             AppendRotationX(ObjectToMove->XformToWorld,
+                   ObjectToMove->Rotate.RotateX);
+          if (ObjectToMove->Rotate.RotateY != 0.0)
+             AppendRotationY(ObjectToMove->XformToWorld,
+                   ObjectToMove->Rotate.RotateY);
+          if (ObjectToMove->Rotate.RotateZ != 0.0)
+             AppendRotationZ(ObjectToMove->XformToWorld,
+                   ObjectToMove->Rotate.RotateZ);
+          ObjectToMove->RecalcXform = 1;
+       }
+       /* Move in Z, checking for bouncing and stopping */
+       if (--ObjectToMove->MDelayCount == 0) {
+          ObjectToMove->MDelayCount = ObjectToMove->MDelayCountBase;
+          ObjectToMove->XformToWorld[2][3] += ObjectToMove->Move.MoveZ;
+          if (ObjectToMove->XformToWorld[2][3]>ObjectToMove->Move.MaxZ)
+             ObjectToMove->Move.MoveZ = 0; /* stop if close enough */
+          ObjectToMove->RecalcXform = 1;
+       }
+    }
+
+**LISTING 52.7 L52-7.C**
+
+    /* Draws all visible faces in specified polygon-based object. Object must have
+       previously been transformed and projected, so that ScreenVertexList array is
+       filled in. */
+
+    #include “polygon.h”
+
+    void DrawPObject(PObject * ObjectToXform)
+    {
+       int i, j, NumFaces = ObjectToXform->NumFaces, NumVertices;
+       int * VertNumsPtr;
+       Face * FacePtr = ObjectToXform->FaceList;
+       Point * ScreenPoints = ObjectToXform->ScreenVertexList;
+       long v1, v2, w1, w2;
+       Point Vertices[MAX_POLY_LENGTH];
+       PointListHeader Polygon;
+
+       /* Draw each visible face (polygon) of the object in turn */
+       for (i=0; i<NumFaces; i++, FacePtr++) {
+          NumVertices = FacePtr->NumVerts;
+          /* Copy over the face's vertices from the vertex list */
+          for (j=0, VertNumsPtr=FacePtr->VertNums; j<NumVertices; j++)
+             Vertices[j] = ScreenPoints[*VertNumsPtr++];
+          /* Draw only if outside face showing (if the normal to the
+             polygon points toward viewer; that is, has a positive Z component) */
+          v1 = Vertices[1].X - Vertices[0].X;
+          w1 = Vertices[NumVertices-1].X - Vertices[0].X;
+          v2 = Vertices[1].Y - Vertices[0].Y;
+          w2 = Vertices[NumVertices-1].Y - Vertices[0].Y;
+          if ((v1*w2 - v2*w1) > 0) {
+             /* It is facing the screen, so draw */
+             /* Appropriately adjust the extent of the rectangle used to
+                erase this object later */
+             for (j=0; j<NumVertices; j++) {
+                if (Vertices[j].X >
+                      ObjectToXform->EraseRect[NonDisplayedPage].Right)
+                   if (Vertices[j].X < SCREEN_WIDTH)
+                      ObjectToXform->EraseRect[NonDisplayedPage].Right =
+                            Vertices[j].X;
+                   else ObjectToXform->EraseRect[NonDisplayedPage].Right =
+                         SCREEN_WIDTH;
+                if (Vertices[j].Y >
+                      ObjectToXform->EraseRect[NonDisplayedPage].Bottom)
+                   if (Vertices[j].Y < SCREEN_HEIGHT)
+                      ObjectToXform->EraseRect[NonDisplayedPage].Bottom =
+                            Vertices[j].Y;
+                   else ObjectToXform->EraseRect[NonDisplayedPage].Bottom=
+                         SCREEN_HEIGHT;
+                if (Vertices[j].X <
+                      ObjectToXform->EraseRect[NonDisplayedPage].Left)
+                   if (Vertices[j].X > 0)
+                      ObjectToXform->EraseRect[NonDisplayedPage].Left =
+                            Vertices[j].X;
+                   else ObjectToXform->EraseRect[NonDisplayedPage].Left=0;
+                if (Vertices[j].Y <
+                      ObjectToXform->EraseRect[NonDisplayedPage].Top)
+                   if (Vertices[j].Y > 0)
+                      ObjectToXform->EraseRect[NonDisplayedPage].Top =
+                            Vertices[j].Y;
+                   else ObjectToXform->EraseRect[NonDisplayedPage].Top=0;
+             }
+             /* Draw the polygon */
+             DRAW_POLYGON(Vertices, NumVertices, FacePtr->Color, 0, 0);
+          }
+       }
+    }
+
+  ------------------------ --------------------------------- --------------------
+  [Previous](52-03.html)   [Table of Contents](index.html)   [Next](52-05.html)
+  ------------------------ --------------------------------- --------------------
+
+* * * * *
+
+Graphics Programming Black Book © 2001 Michael Abrash