Android development-OpenGL ES 3D space and glDrawArrays

1. Four pyramid: composed of four triangles.

Ry: consists of six triangles.

Difficulty: when constructing the vertex coordinates of a 3D space, to make the object rotate around its own axis, the central coordinates of the object must always be (0.0f, 0.0f, 0.0f ),

And the triangles are drawn in a counter-clockwise order.

2.3D space rendering:

GL_APICALL void GL_APIENTRY glDrawArrays (GLenum mode, GLint first, GLsizei count );

Parameter description:

Mode: drawing method. The following parameters are provided after OpenGL2.0: GL_POINTS, GL_LINES, GL_LINE_LOOP, GL_LINE_STRIP, GL_TRIANGLES, GL_TRIANGLE_STRIP, and GL_TRIANGLE_FAN.

First, which position in the array cache is drawn, generally 0.

Count, number of vertices in the array.

3. Draw the vertex array:

// Draw a triangle cone

For (int I = 0; I <4; I ++)

{

Gl. glDrawArrays (GL10.GL _ TRIANGLE_STRIP, I * 3, 3 );

}

// Draw a ry

For (int I = 0; I <6; I ++)

{

Gl. glDrawArrays (GL10.GL _ TRIANGLE_STRIP, I * 4, 4 );

}

[Appendix] constructing vertex Arrays:

[Java]

Int one = 0x10000;

// An array of four pyramid vertices:

Private IntBuffer triggerBuffer = IntBuffer. wrap (new int [] {

0, one, 0,

-One,-one, 0,

One,-one, one,

0, one, 0,

One,-one, one,

One,-one,-one,

0, one, 0,

One,-one,-one,

-One,

0, one, 0,

-One,

-One,-one, one

});

// An array of Four-body vertices:

Private IntBuffer quaterBuffer = IntBuffer. wrap (new int [] {

One, one,-one,

-One, one,-one,

One,

-One,

One,-one, one,

-One,-one, one,

One,-one,-one,

-One,

One,

-One,

One,-one, one,

-One,-one, one,

One,-one,-one,

-One,

One, one,-one,

-One, one,-one,

-One,

-One, one,-one,

-One,-one, one,

-One,

One, one,-one,

One,

One,-one,-one,

One,-one, one,

});

Int one = 0x10000;

// An array of four pyramid vertices:

Private IntBuffer triggerBuffer = IntBuffer. wrap (new int [] {

0, one, 0,

-One,-one, 0,

One,-one, one,

0, one, 0,

One,-one, one,

One,-one,-one,

0, one, 0,

One,-one,-one,

-One,

0, one, 0,

-One,

-One,-one, one

});

// An array of Four-body vertices:

Private IntBuffer quaterBuffer = IntBuffer. wrap (new int [] {

One, one,-one,

-One, one,-one,

One,

-One,

One,-one, one,

-One,-one, one,

One,-one,-one,

-One,

One,

-One,

One,-one, one,

-One,-one, one,

One,-one,-one,

-One,

One, one,-one,

-One, one,-one,

-One,

-One, one,-one,

-One,-one, one,

-One,

One, one,-one,

One,

One,-one,-one,

One,-one, one,

});