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PODoesn't move and rotate the triangle around a point - C Bgi graphics
 

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  1. PODoesn't move and rotate the triangle around a point - C Bgi graphics
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    <p>Greeting,</p> <p>I have this graphic homework in BGI graphic. We must use DevCPP and BGI, and matrices.</p> <p>I wrote this code, and I think the transformations is good. But my triangle doesn't move and rotate around the circle, And I don't understand, why not it moves around the circle...</p> <p>I don't know where and what I have to rewrite.</p> <pre><code>#include &lt;math.h&gt; #include "graphics.h" #include &lt;stdio.h&gt; #include &lt;stdlib.h&gt; #include &lt;conio.h&gt; #define PI 3.14159265 typedef float Matrix3x3[3][3]; Matrix3x3 theMatrix; int Round( double n ){ return (int)( n + 0.5 ); } void matrix3x3SetIdentity(Matrix3x3 m) { int i, j; for(i=0; i&lt;3; i++) for(j=0; j&lt;3;j++) m[i][j]=(i==j); } /* Multiplies matrix, result in b matrix */ void matrix3x3PreMultiply(Matrix3x3 a, Matrix3x3 b) { int r, c; Matrix3x3 tmp; for(r=0; r&lt;3;r++) for(c=0; c&lt;3;c++) tmp[r][c]= a[r][0]*b[0][c]+a[r][1]*b[1][c]+a[r][2]*b[2][c]; for(r=0; r&lt;3;r++) for(c=0; c&lt;3; c++) b[r][c]-tmp[r][c]; } void translate2(int tx, int ty) { Matrix3x3 m; matrix3x3SetIdentity (m); m[0][2] = tx; m[1][2] = ty; matrix3x3PreMultiply(m, theMatrix); } void scale2 (float sx, float sy, pont2d refpt) { Matrix3x3 m; matrix3x3SetIdentity(m); m[0][0]=sx; m[0][2]=(1-sx)*refpt.x; m[1][1]=sy; m[1][2]=(1-sy)*refpt.y; matrix3x3PreMultiply(m, theMatrix); } void rotate2 (float a, pont2d refpt) { Matrix3x3 m; matrix3x3SetIdentity(m); a=a/PI; m[0][0] = cosf(a); m[0][1] = -sinf(a); m[0][2] = refpt.x * (1-cosf(a)) + refpt.y * sinf(a); m[1][0] = sinf (a); m[1][1] = cosf (a); m[1][2] = refpt.y * (1-cosf(a)) - refpt.x * sinf(a); matrix3x3PreMultiply(m, theMatrix); } void transformPoints2 (int npts, pont2d *pts) { int k; float tmp; for (k = 0; k &lt; npts; k++) { tmp = theMatrix[0][0] * pts[k].x + theMatrix[0][1] * pts[k].y + theMatrix[0][2]; pts[k].y = theMatrix[1][0] * pts[k].x + theMatrix[1][1] * pts[k].y + theMatrix[1][2]; pts[k].x = tmp; } } int main() { int gd, gm, i, page=0; gd=VGA;gm=VGAHI; initgraph(&amp;gd,&amp;gm,""); int ap; while(!kbhit()) { setactivepage(page); cleardevice(); pont2d P[3] = { 50.0, 50.0, 150.0, 50.0, 100.0, 150.0}; pont2d refPt = {200.0, 250.0}; // Drawing the Triangle moveto( Round( P[ 0 ].x ), Round( P[ 0 ].y ) ); for( i = 1; i &lt; 3; i++ ) lineto( Round( P[ i ].x ), Round( P[ i ].y ) ); lineto( Round( P[ 0 ].x ), Round( P[ 0 ].y ) ); // Drawing the Circle fillellipse(200, 250, 5,5); setcolor (BLUE); matrix3x3SetIdentity (theMatrix); scale2 (0.5, 0.5, refPt); //scale2 (20, 20, refPt); rotate2 (90.0, refPt); translate2 (0, 150); transformPoints2 (3, P); setvisualpage(page); page = 1-page; } getch(); closegraph(); return 0; } </code></pre>
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