this question:
the parametric equation on below sets curve t ∈ r:
x(t) = sin(t) + 1/2 sin(5t) + 1/4 cos(2,3t)
y(t) = cos(t) + 1/2 cos(5t) + 1/4 sin(2,3t)
use gl_line_strip white curve , gl_points last calculated point in red. drawn should drawing in real time, means, @ every moment, new point calculates , that, see curve being constructed, picture below. use callback timer 10 millisecond waiting time. clue: use ortho range -2.0 2.0 in x , y.
my code done, 2 issues.
the first 1 is: image not in curve! it's creating straight lines between calculated points. don't know if did formula wrong, if it's missing parenthesis in somewhere or that.
the second 1 is: red point being created, old 1 still there. need in order remove old ones, not big problem, first 1 crazing me out.
this code: ps: comments in portuguese first language.
#include <gl/glut.h> #include <stdlib.h> #include <math.h> void display(void); void init(void); void reshape (int w, int h); void desenhaeixos(); void projecao(void); void desenhacurvalinha(float centerx, float centery); void timer (int i); void desenhaponto(float centerx, float centery); float minx = -2; //parâmetros glortho float maxx = 2; float miny = -2; float maxy = 2; float minz = -1; float maxz = 1; int k = 0; int main(int argc, char *argv[]){ //escopo de criação de janela glutinit(&argc, argv);//avisa que será criada uma janela glutinitwindowsize(500,500); //diz o tamanho da janela glutinitwindowposition(10,10); //diz onde janela vai abrir na tela, em pixel glutinitdisplaymode(glut_rgb | glut_double | glut_depth); //prepara o sistema para janela ser criada, é extremamente importante glutcreatewindow("freeglut shapes");//cria janela //escopo de registro de callbacks glutdisplayfunc(display); glutreshapefunc(reshape); //glutidlefunc(idle); gluttimerfunc(1000/*valor em milesegundos*/, timer, 1); //demais init(); glutmainloop();//fica esperando ação usuário return exit_success; } void display(void){ glclear(gl_color_buffer_bit);//limpando o buffer de cor desenhacurvalinha(1, 1); desenhaponto(1, 1); glutswapbuffers(); } void init(void){ glclearcolor(0,0,0,0);//escolhe cor fundo da janela, nesse caso, preto } void desenhaeixos(){ //gllinewidth(3); //caso queira mudar espessura da linha glbegin(gl_lines); //indica que vou desenhar linhas glcolor3f(1,0,0); // vermelho glvertex3f(minx, 0, 0); //estamos escrevendo o eixo x na tela glvertex3f(maxx, 0, 0);// fui mínimo até o máximo, da esquerda da tela até direita glcolor3f(0,1,0); //verde glvertex3f( 0, miny, 0); glvertex3f( 0, maxy, 0); glcolor3f(0,0,1); //azul glvertex3f( 0, 0, minz); glvertex3f( 0, 0, maxz); glend(); } void desenhacurvalinha(float centerx, float centery){ float x, y; int t; glcolor3f(1,1,1); glbegin(gl_line_strip); for(t=0;t<=k;t++){ x = sin(t) + 0.5 * sin (5 * t) + 0.25 * cos (2.3*t); y = cos(t) + 0.5 * cos (5 * t) + 0.25 * sin (2.3*t); glvertex2f(x, y); } glend(); } void desenhaponto(float centerx, float centery){ float x, y; int t; glpointsize(5); glcolor3f(1,0,0); glbegin(gl_points); for(t=0;t<=k;t++){ x = sin(t) + 0.5 * sin (5 * t) + 0.25 * cos (2.3*t); y = cos(t) + 0.5 * cos (5 * t) + 0.25 * sin (2.3*t); glvertex2f(x, y); } glend(); } void reshape (int w, int h){ glviewport(0,0,w,h); //linha protocolo projecao(); } void projecao(void){ glmatrixmode(gl_projection); glloadidentity(); glortho(minx, maxx, miny, maxy, minz, maxz); // diz agora, que o x da minha janela começa no -10 e termina no 10, o y também. glmatrixmode(gl_modelview); glloadidentity(); } void timer (int i){ k++; glutpostredisplay(); gluttimerfunc(1000, timer, 1); }
you straight lines between points because you're drawing straight lines between points (and that's can on pixel display).
the t in formula continuous, t ∈ r.
t isn't, , can't because you're using digital computer.
for smoother "curve", use smaller steps 1 between points on line.
you're drawing many points because you're using loop draws points on curve (i suspect copy-and-paste involved).
remove loop in desenhaponto , draw last point, t = k:
glbegin(gl_points); x = sin(k) + 0.5 * sin (5 * k) + 0.25 * cos (2.3*k); y = cos(k) + 0.5 * cos (5 * k) + 0.25 * sin (2.3*k); glvertex2f(x, y); glend(); 
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