Teach Yourself Game Programming in 21 Days

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C/C++ Source or Header | 1994-06-13 | 16.6 KB | 745 lines

// I N C L U D E S /////////////////////////////////////////////////////////// #include <io.h> #include <conio.h> #include <stdio.h> #include <stdlib.h> #include <dos.h> #include <bios.h> #include <fcntl.h> #include <memory.h> #include <malloc.h> #include <math.h> #include <string.h> #include "graph3.h" // include our graphics stuff #include "graph4.h" #include "graph5.h" // G L O B A L S //////////////////////////////////////////////////////////// float sin_look[361], // look up tables for sin and cosine cos_look[361]; // the clipping region, set it to default on start up int poly_clip_min_x = POLY_CLIP_MIN_X, poly_clip_min_y = POLY_CLIP_MIN_Y, poly_clip_max_x = POLY_CLIP_MAX_X, poly_clip_max_y = POLY_CLIP_MAX_Y; // F U N C T I O N S ///////////////////////////////////////////////////////// void Create_Tables(void) { // this function creates the sin and cosine lookup tables int index; // create the tables for (index=0; index<=360; index++) { cos_look[index] = (float)cos((double)(index*3.14159/180)); sin_look[index] = (float)sin((double)(index*3.14159/180)); } // end for } // end Create_Tables ////////////////////////////////////////////////////////////////////////////// void Rotate_Polygon(polygon_ptr poly, int angle) { int index; // loop index float si,cs, // values of sin and cosine rx,ry; // roated points // rotate each point of the poly gon around its local origin // note that angle is an integer and ranges from -360 to +360 // compute sin and cos of angle to be rotated if (angle>=0) { // extract sin and cosine from look up table si = sin_look[angle]; cs = cos_look[angle]; } // end if positive angle else { // angle is negative to convert to positive // convert negative angle to positive angle and extract values si = sin_look[angle+360]; cs = cos_look[angle+360]; } // end else // using values for sin and cosine rotate the point for (index=0; index<poly->num_vertices; index++) { // compute rotated values using rotation eqns. rx = poly->vertices[index].x * cs - poly->vertices[index].y * si; ry = poly->vertices[index].y * cs + poly->vertices[index].x * si; // store the rotated vertex back into structure poly->vertices[index].x = rx; poly->vertices[index].y = ry; } // end for } // end Rotate_Polygon /////////////////////////////////////////////////////////////////////////////// void Scale_Polygon(polygon_ptr poly, float scale) { int index; // scale each vertex of the polygon for (index=0; index<poly->num_vertices; index++) { // multiply by the scaling factor poly->vertices[index].x*=scale; poly->vertices[index].y*=scale; } // end for } // end Scale_Polygon /////////////////////////////////////////////////////////////////////////////// void Translate_Polygon(polygon_ptr poly, int dx,int dy) { // translate the origin of the polygon poly->lxo+=dx; poly->lyo+=dy; // that was easy! } // end Translate_Polygon /////////////////////////////////////////////////////////////////////////////// void Draw_Polygon(polygon_ptr poly) { // this function draws a polygon on the screen without clipping // caller should make sure that vertices are within bounds of clipping // rectangle, also the polygon will always be unfilled regardless // of the fill flag int index,xo,yo; // extract local origin xo = poly->lxo; yo = poly->lyo; // draw polygon for (index=0; index<poly->num_vertices-1; index++) { Bline(xo+(int)poly->vertices[index].x,yo+(int)poly->vertices[index].y, xo+(int)poly->vertices[index+1].x,yo+(int)poly->vertices[index+1].y, poly->b_color); } // end for index // close polygon? if (!poly->closed) return; Bline(xo+(int)poly->vertices[index].x,yo+(int)poly->vertices[index].y, xo+(int)poly->vertices[0].x,yo+(int)poly->vertices[0].y, poly->b_color); } // end Draw_Polygon ////////////////////////////////////////////////////////////////////////////// int Clip_Line(int *x1,int *y1,int *x2, int *y2) { // this function clips the sent line using the globally defined clipping // region int point_1 = 0, point_2 = 0; // tracks if each end point is visible or invisible int clip_always = 0; // used for clipping override int xi,yi; // point of intersection int right_edge=0, // which edges are the endpoints beyond left_edge=0, top_edge=0, bottom_edge=0; int success = 0; // was there a successfull clipping float dx,dy; // used to holds slope deltas // SECTION 1 ////////////////////////////////////////////////////////////////// // test if line is completely visible if ( (*x1>=poly_clip_min_x) && (*x1<=poly_clip_max_x) && (*y1>=poly_clip_min_y) && (*y1<=poly_clip_max_y) ) point_1 = 1; if ( (*x2>=poly_clip_min_x) && (*x2<=poly_clip_max_x) && (*y2>=poly_clip_min_y) && (*y2<=poly_clip_max_y) ) point_2 = 1; // SECTION 2 ///////////////////////////////////////////////////////////////// // test endpoints if (point_1==1 && point_2==1) return(1); // SECTION 3 ///////////////////////////////////////////////////////////////// // test if line is completely invisible if (point_1==0 && point_2==0) { // must test to see if each endpoint is on the same side of one of // the bounding planes created by each clipping region boundary if ( ((*x1<poly_clip_min_x) && (*x2<poly_clip_min_x)) || // to the left ((*x1>poly_clip_max_x) && (*x2>poly_clip_max_x)) || // to the right ((*y1<poly_clip_min_y) && (*y2<poly_clip_min_y)) || // above ((*y1>poly_clip_max_y) && (*y2>poly_clip_max_y)) ) // below { // no need to draw line return(0); } // end if invisible // if we got here we have the special case where the line cuts into and // out of the clipping region clip_always = 1; } // end if test for invisibly // SECTION 4 ///////////////////////////////////////////////////////////////// // take care of case where either endpoint is in clipping region if (( point_1==1) || (point_1==0 && point_2==0) ) { // compute deltas dx = *x2 - *x1; dy = *y2 - *y1; // compute what boundary line need to be clipped against if (*x2 > poly_clip_max_x) { // flag right edge right_edge = 1; // compute intersection with right edge if (dx!=0) yi = (int)(.5 + (dy/dx) * (poly_clip_max_x - *x1) + *y1); else yi = -1; // invalidate intersection } // end if to right else if (*x2 < poly_clip_min_x) { // flag left edge left_edge = 1; // compute intersection with left edge if (dx!=0) yi = (int)(.5 + (dy/dx) * (poly_clip_min_x - *x1) + *y1); else yi = -1; // invalidate intersection } // end if to left // horizontal intersections if (*y2 > poly_clip_max_y) { // flag bottom edge bottom_edge = 1; // compute intersection with right edge if (dy!=0) xi = (int)(.5 + (dx/dy) * (poly_clip_max_y - *y1) + *x1); else xi = -1; // invalidate inntersection } // end if bottom else if (*y2 < poly_clip_min_y) { // flag top edge top_edge = 1; // compute intersection with top edge if (dy!=0) xi = (int)(.5 + (dx/dy) * (poly_clip_min_y - *y1) + *x1); else xi = -1; // invalidate inntersection } // end if top // SECTION 5 ///////////////////////////////////////////////////////////////// // now we know where the line passed thru // compute which edge is the proper intersection if (right_edge==1 && (yi>=poly_clip_min_y && yi<=poly_clip_max_y) ) { *x2 = poly_clip_max_x; *y2 = yi; success = 1; } // end if intersected right edge else if (left_edge==1 && (yi>=poly_clip_min_y && yi<=poly_clip_max_y) ) { *x2 = poly_clip_min_x; *y2 = yi; success = 1; } // end if intersected left edge if (bottom_edge==1 && (xi>=poly_clip_min_x && xi<=poly_clip_max_x) ) { *x2 = xi; *y2 = poly_clip_max_y; success = 1; } // end if intersected bottom edge else if (top_edge==1 && (xi>=poly_clip_min_x && xi<=poly_clip_max_x) ) { *x2 = xi; *y2 = poly_clip_min_y; success = 1; } // end if intersected top edge } // end if point_1 is visible // SECTION 6 ///////////////////////////////////////////////////////////////// // reset edge flags right_edge = left_edge= top_edge = bottom_edge = 0; // test second endpoint if ( (point_2==1) || (point_1==0 && point_2==0)) { // compute deltas dx = *x1 - *x2; dy = *y1 - *y2; // compute what boundary line need to be clipped against if (*x1 > poly_clip_max_x) { // flag right edge right_edge = 1; // compute intersection with right edge if (dx!=0) yi = (int)(.5 + (dy/dx) * (poly_clip_max_x - *x2) + *y2); else yi = -1; // invalidate inntersection } // end if to right else if (*x1 < poly_clip_min_x) { // flag left edge left_edge = 1; // compute intersection with left edge if (dx!=0) yi = (int)(.5 + (dy/dx) * (poly_clip_min_x - *x2) + *y2); else yi = -1; // invalidate intersection } // end if to left // horizontal intersections if (*y1 > poly_clip_max_y) { // flag bottom edge bottom_edge = 1; // compute intersection with right edge if (dy!=0) xi = (int)(.5 + (dx/dy) * (poly_clip_max_y - *y2) + *x2); else xi = -1; // invalidate inntersection } // end if bottom else if (*y1 < poly_clip_min_y) { // flag top edge top_edge = 1; // compute intersection with top edge if (dy!=0) xi = (int)(.5 + (dx/dy) * (poly_clip_min_y - *y2) + *x2); else xi = -1; // invalidate inntersection } // end if top // now we know where the line passed thru // compute which edge is the proper intersection if (right_edge==1 && (yi>=poly_clip_min_y && yi<=poly_clip_max_y) ) { *x1 = poly_clip_max_x; *y1 = yi; success = 1; } // end if intersected right edge else if (left_edge==1 && (yi>=poly_clip_min_y && yi<=poly_clip_max_y) ) { *x1 = poly_clip_min_x; *y1 = yi; success = 1; } // end if intersected left edge if (bottom_edge==1 && (xi>=poly_clip_min_x && xi<=poly_clip_max_x) ) { *x1 = xi; *y1 = poly_clip_max_y; success = 1; } // end if intersected bottom edge else if (top_edge==1 && (xi>=poly_clip_min_x && xi<=poly_clip_max_x) ) { *x1 = xi; *y1 = poly_clip_min_y; success = 1; } // end if intersected top edge } // end if point_2 is visible // SECTION 7 ///////////////////////////////////////////////////////////////// return(success); } // end Clip_Line ////////////////////////////////////////////////////////////////////////////// void Draw_Polygon_Clip(polygon_ptr poly) { // this function draws a polygon on the screen with clipping // also the polygon will always be unfilled regardless // of the fill flag in the polygon structure int index, // loop index xo,yo, // local origin x1,y1, // end points of current line being processed x2,y2; // extract local origin xo = poly->lxo; yo = poly->lyo; // draw polygon for (index=0; index<poly->num_vertices-1; index++) { // extract the line x1 = (int)poly->vertices[index].x+xo; y1 = (int)poly->vertices[index].y+yo; x2 = (int)poly->vertices[index+1].x+xo; y2 = (int)poly->vertices[index+1].y+yo; // clip line to viewing screen and draw unless line is totally invisible if (Clip_Line(&x1,&y1,&x2,&y2)) { // line was clipped and now can be drawn Bline(x1,y1,x2,y2,poly->b_color); } // end if draw line } // end for index // close polygon? // close polygon if (!poly->closed) return; // extract the line x1 = (int)poly->vertices[index].x+xo; y1 = (int)poly->vertices[index].y+yo; x2 = (int)poly->vertices[0].x+xo; y2 = (int)poly->vertices[0].y+yo; // clip line to viewing screen and draw unless line is totally invisible if (Clip_Line(&x1,&y1,&x2,&y2)) { // line was clipped and now can be drawn Bline(x1,y1,x2,y2,poly->b_color); } // end if draw line } // end Draw_Polygon_Clip ////////////////////////////////////////////////////////////////////////////// void Bline(int xo, int yo, int x1,int y1, unsigned char color) { // this function uses Bresenham's algorithm IBM (1965) to draw a line from // (xo,yo) - (x1,y1) int dx, // difference in x's dy, // difference in y's x_inc, // amount in pixel space to move during drawing y_inc, // amount in pixel space to move during drawing error=0, // the discriminant i.e. error i.e. decision variable index; // used for looping unsigned char far *vb_start = video_buffer; // directly access the video // buffer for speed // SECTION 1 ///////////////////////////////////////////////////////////////// // pre-compute first pixel address in video buffer // use shifts for multiplication vb_start = vb_start + ((unsigned int)yo<<6) + ((unsigned int)yo<<8) + (unsigned int)xo; // compute deltas dx = x1-xo; dy = y1-yo; // SECTION 2 ///////////////////////////////////////////////////////////////// // test which direction the line is going in i.e. slope angle if (dx>=0) { x_inc = 1; } // end if line is moving right else { x_inc = -1; dx = -dx; // need absolute value } // end else moving left // SECTION 3 ///////////////////////////////////////////////////////////////// // test y component of slope if (dy>=0) { y_inc = 320; // 320 bytes per line } // end if line is moving down else { y_inc = -320; dy = -dy; // need absolute value } // end else moving up // SECTION 4 ///////////////////////////////////////////////////////////////// // now based on which delta is greater we can draw the line if (dx>dy) { // draw the line for (index=0; index<=dx; index++) { // set the pixel *vb_start = color; // adjust the discriminate error+=dy; // test if error overflowed if (error>dx) { error-=dx; // move to next line vb_start+=y_inc; } // end if error overflowed // move to the next pixel vb_start+=x_inc; } // end for } // end if |slope| <= 1 else { // SECTION 5 ///////////////////////////////////////////////////////////////// // draw the line for (index=0; index<=dy; index++) { // set the pixel *vb_start = color; // adjust the discriminate error+=dx; // test if error overflowed if (error>0) { error-=dy; // move to next line vb_start+=x_inc; } // end if error overflowed // move to the next pixel vb_start+=y_inc; } // end for } // end else |slope| > 1 } // end Bline /////////////////////////////////////////////////////////////////////////////// void Draw_Boundary(int color) { // draws in the clipping boundary if user is intersted in seeing it Bline(poly_clip_min_x,poly_clip_min_y, poly_clip_max_x,poly_clip_min_y,color); Bline(poly_clip_max_x,poly_clip_min_y, poly_clip_max_x,poly_clip_max_y,color); Bline(poly_clip_max_x,poly_clip_max_y, poly_clip_min_x,poly_clip_max_y,color); Bline(poly_clip_min_x,poly_clip_max_y, poly_clip_min_x,poly_clip_min_y,color); } // end Draw_Boundary ///////////////////////////////////////////////////////////////////////////////