OpenGL.rar_OPENGL 二维

#include <GL/glut.h> #include <stdlib.h> #include <math.h> /* 生成窗口尺寸 */ GLsizei winWidth = 600, winHeight = 600; /* 二维坐标系上显示在窗口中的范围 */ GLfloat xwcMin = 0.0, xwcMax = 225.0; GLfloat ywcMin = 0.0, ywcMax = 225.0; struct wcPt2D { GLfloat x, y; }; typedef GLfloat Matrix3x3 [3][3]; Matrix3x3 matComposite; const GLdouble pi = 3.14159; void init (void) { /* 设置清空颜色为白色 */ glClearColor (1.0, 1.0, 1.0, 0.0); } /* 初始二维变换单位矩阵 */ void matrix3x3SetIdentity (Matrix3x3 matIdent3x3) { GLint row, col; for (row = 0; row < 3; row++) for (col = 0; col < 3; col++) matIdent3x3 [row][col] = (row == col); } /* 矩阵m1乘以m2，结果保存在m2 */ 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; /* 初始化为单位矩阵 */ matrix3x3SetIdentity (matTransl); matTransl [0][2] = tx; matTransl [1][2] = ty; /* Concatenate matTransl with the composite matrix. */ matrix3x3PreMultiply (matTransl, matComposite); } void rotate2D (wcPt2D pivotPt, GLfloat theta) { Matrix3x3 matRot; /* Initialize rotation matrix to identity. */ 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); /* Concatenate matRot with the composite matrix. */ matrix3x3PreMultiply (matRot, matComposite); } void scale2D (GLfloat sx, GLfloat sy, wcPt2D fixedPt) { Matrix3x3 matScale; /* Initialize scaling matrix to identity. */ matrix3x3SetIdentity (matScale); matScale [0][0] = sx; matScale [0][2] = (1 - sx) * fixedPt.x; matScale [1][1] = sy; matScale [1][2] = (1 - sy) * fixedPt.y; /* Concatenate matScale with the composite matrix. */ matrix3x3PreMultiply (matScale, matComposite); } /* Using the composite matrix, calculate transformed coordinates. */ 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) { GLint k; glBegin (GL_TRIANGLES); for (k = 0; k < 3; k++) glVertex2f (verts [k].x, verts [k].y); glEnd ( ); } void displayFcn (void) { /* Define initial position for triangle. */ GLint nVerts = 3; wcPt2D verts [3] = { {50.0, 25.0}, {150.0, 25.0}, {100.0, 100.0} }; /* Calculate position of triangle centroid. */ wcPt2D centroidPt; GLint k, xSum = 0, ySum = 0; for (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); /* Set geometric transformation parameters. */ wcPt2D pivPt, fixedPt; pivPt = centroidPt; fixedPt = centroidPt; GLfloat tx = 0.0, ty = 100.0; GLfloat sx = 0.5, sy = 0.5; GLdouble theta = pi/2.0; glClear (GL_COLOR_BUFFER_BIT); // Clear display window. glColor3f (0.0, 0.0, 1.0); // Set initial fill color to blue. triangle (verts); // Display blue triangle. /* Initialize composite matrix to identity. */ matrix3x3SetIdentity (matComposite); /* Construct composite matrix for transformation sequence. */ scale2D (sx, sy, fixedPt); // First transformation: Scale. rotate2D (pivPt, theta); // Second transformation: Rotate translate2D (tx, ty); // Final transformation: Translate. /* Apply composite matrix to triangle vertices. */ transformVerts2D (nVerts, verts); glColor3f (1.0, 0.0, 0.0); // Set color for transformed triangle. triangle (verts); // Display red transformed triangle. glFlush ( ); } void winReshapeFcn (GLint newWidth, GLint newHeight) { glMatrixMode (GL_PROJECTION); glLoadIdentity ( ); gluOrtho2D (xwcMin, xwcMax, ywcMin, ywcMax); glClear (GL_COLOR_BUFFER_BIT); } void main (int argc, char ** argv) { glutInit (&argc, argv); glutInitDisplayMode (GLUT_SINGLE | GLUT_RGB); glutInitWindowPosition (50, 50); glutInitWindowSize (winWidth, winHeight); glutCreateWindow ("Geometric Transformation Sequence"); init ( ); glutDisplayFunc (displayFcn); glutReshapeFunc (winReshapeFcn); glutMainLoop ( ); }