OpenGL——二维几何变换

平移、旋转、缩放的实现

#include<iostream>
#include <math.h>
#include<Windows.h>
#include <GL/glut.h>using namespace std;GLsizei winWidth = 600, winHeight = 600;GLfloat xwcMin = 0.0, xwcMax = 225.0;
GLfloat ywcMin = 0.0, ywcMax = 225.0;class wcPt2D {
public:GLfloat x, y;
};typedef GLfloat Matrix3x3[3][3];Matrix3x3 matComposite;const GLdouble pi = 3.14159;void init()
{//窗口背景为白色glClearColor(1.0, 1.0, 1.0, 0.0);
}void matrix3x3SetIdentity(Matrix3x3 matIdent3x3)
{GLint row, col;for (row = 0; row < 3; row++) {for (col = 0; col < 3; col++) {matIdent3x3[row][col] = (row == col);}}
}void matrix3x3PreMultiply(Matrix3x3 m1, Matrix3x3 m2)
{GLint row, col;Matrix3x3 matTemp;for (row = 0; row < 3; row++) {for (col = 0; col < 3; col++) {matTemp[row][col] = m1[row][0] * m2[0][col] + m1[row][1] * m2[1][col] +m1[row][2] * m2[2][col];}}for (row = 0; row < 3; row++) {for (col = 0; col < 3; col++) {m2[row][col] = matTemp[row][col];}}
}void translate2D(GLfloat tx, GLfloat ty)
{Matrix3x3 matTransl;matrix3x3SetIdentity(matTransl);matTransl[0][2] = tx;matTransl[1][2] = ty;matrix3x3PreMultiply(matTransl, matComposite);
}void rotate2D(wcPt2D pivotPt, GLfloat theta)
{Matrix3x3 matRot;matrix3x3SetIdentity(matRot);matRot[0][0] = cos(theta);matRot[0][1] = -sin(theta);matRot[0][2] = pivotPt.x * (1 - cos(theta)) + pivotPt.y * sin(theta);matRot[1][0] = sin(theta);matRot[1][1] = cos(theta);matRot[1][2] = pivotPt.y * (1 - cos(theta)) - pivotPt.x * sin(theta);matrix3x3PreMultiply(matRot, matComposite);
}void scale2D(GLfloat sx, GLfloat sy, wcPt2D fixedPt)
{Matrix3x3 matScale;matrix3x3SetIdentity(matScale);matScale[0][0] = sx;matScale[0][2] = (1 - sx) * fixedPt.x;matScale[1][1] = sy;matScale[1][2] = (1 - sy) * fixedPt.y;matrix3x3PreMultiply(matScale, matComposite);
}void transformVerts2D(GLint nVerts, wcPt2D * verts)
{GLint k;GLfloat temp;for (k = 0; k < nVerts; k++) {temp = matComposite[0][0] * verts[k].x + matComposite[0][1] * verts[k].y + matComposite[0][2];verts[k].y = matComposite[1][0] * verts[k].x + matComposite[1][1] * verts[k].y + matComposite[1][2];verts[k].x = temp;}
}void triangle(wcPt2D *verts)
{glBegin(GL_TRIANGLES);for (GLint k = 0; k < 3; k++) {glVertex2f(verts[k].x, verts[k].y);}glEnd();
}void displayFcn()
{    GLint nVerts = 3;wcPt2D verts[3] = { {50.0,25.0},{150.0,25.0},{100.0,100.0} };wcPt2D centroidPt;GLint xSum = 0, ySum = 0;for (GLint k = 0; k < nVerts; k++) {xSum += verts[k].x;ySum += verts[k].y;}centroidPt.x = GLfloat(xSum) / GLfloat(nVerts);centroidPt.y = GLfloat(ySum) / GLfloat(nVerts);wcPt2D pivPt, fixedPt;pivPt = centroidPt;fixedPt = centroidPt;GLfloat tx = 0.0, ty = 100.0;GLfloat sx = 0.5, sy = 0.5;GLdouble theta = pi / 2;glClear(GL_COLOR_BUFFER_BIT);glColor3f(200.0 / 255.0, 200.0 / 255.0, 169.0 / 255.0);triangle(verts);matrix3x3SetIdentity(matComposite);scale2D(sx, sy, fixedPt);transformVerts2D(nVerts, verts);glColor3f(137.0 / 255.0, 190.0 / 255.0, 178.0 / 255.0);triangle(verts);matrix3x3SetIdentity(matComposite);rotate2D(pivPt, theta);transformVerts2D(nVerts, verts);glColor3f(69.0 / 255.0, 137.0 / 255.0, 148.0 / 255.0);triangle(verts);matrix3x3SetIdentity(matComposite);translate2D(tx, ty);transformVerts2D(nVerts, verts);glColor3f(178.0 / 255.0, 200.0 / 255.0, 187.0 / 255.0);triangle(verts);glFlush();
}void winReshapeFcn(GLint newWidth, GLint newHeight)
{glMatrixMode(GL_PROJECTION);glLoadIdentity();gluOrtho2D(xwcMin, xwcMax, ywcMin, ywcMax);glClear(GL_COLOR_BUFFER_BIT);
}int main(int argc, char* argv[])
{glutInit(&argc, argv);glutInitDisplayMode(GLUT_RGB | GLUT_SINGLE);glutInitWindowPosition(50, 50);glutInitWindowSize(winWidth, winHeight);glutCreateWindow("二维几何变换");init();glutDisplayFunc(displayFcn);glutReshapeFunc(winReshapeFcn);glutMainLoop();system("pause");return 0;
}

运行结果