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| 5.
CREATE
POLYGON IN OPENGL |
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| 1. |
If we want to create
a Triangle, we have to specify three points, let's say V0
for first point, V1 for second point and V2 for third point.
Identify the coordinate of each of the point. Refer to this
diagram for easier understanding:
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| 2. |
This time in the same
program (main.cpp), replace line 17 (glutSolidCube...) with line
17 to 21 in this program.
GL_TRIANGLES will be used to create the triangle.
glBegin(GL_TRIANGLES);
glVertex3f(
0.0, 0.0, 0.0);
// V0 ( 0,
0, 0 )
glVertex3f(
1.0f, 0.0, 0.0); //
V1 ( 1, 0, 0 )
glVertex3f(
0.5f, 1.0f, 0.0); //
V2 ( 0.5, 1, 0 )
glEnd(); |
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| 3. |
The ouput of the program will be like this:
 |
| 4. |
If we want to create
a Square, we have to specify four points, let's say V0
for first point, V1 for second point, V2 for third point and V3
for fourth point. Identify the coordinate of each of the point.
Refer to this diagram for easier understanding:
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| 5. |
This time in the same
program (main.cpp), replace line 17 (glutSolidCube...) with line
17 to 21 in this program.
GL_QUADS will be used to create the square or rectangle.
glBegin(GL_QUADS);
glVertex3f( 0.0, 0.0, 0.0);
// V0 (0,0,0)
glVertex3f( 1.0f, 0.0, 0.0);
// V1 (1,0,0)
glVertex3f( 1.0f, 1.0f, 0.0);
// V2 (1,1,0)
glVertex3f( 0.0, 1.0f, 0.0);
// V3 (0,1,0)
glEnd();
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| 6. |
The ouput of the program this time will be like
this:
 |
| 7. |
If we want to create
a polygon which have more than four points, we have to specify
all its' points, let's say V0
for first point, V1 for second point, V2 for third point, V3
for fourth point and V4 for the fifth point. Identify the coordinate of each of the point.
Refer to this diagram for easier understanding:
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| 8. |
This time in the same
program (main.cpp), replace line 17 (glutSolidCube...) with line
17 to 21 in this program.
GL_POLYGON will be used to create the polygons which have
more than four points.
glBegin(GL_POLYGON);
glVertex3f( 0.0, 0.0, 0.0);
// V0 ( 0, 0, 0)
glVertex3f( 1.0f, 0.0, 0.0);
// V1 ( 1, 0, 0)
glVertex3f( 1.0f, 1.0f, 0.0);
// V2 ( 1, 1, 0)
glVertex3f( 0.5f, 1.5f, 0.0);
// V3 (0.5, 1.5, 0)
glVertex3f( 0.0, 1.0f, 0.0);
// V4 ( 0, 1, 0)
glEnd(); |
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| 9. |
The ouput of the program will be like this:
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| 10. |
Now, you can try to
combine all of the polygons inside your program. Enjoy :) |
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