不能使用gldrawarray绘图

Cant draw using glDrawArrays

本文关键字：绘图 gldrawarray 不能      更新时间：2023-10-16

为什么这个代码不能工作?

 // 1 square (made by 4 quads) to be rendered
GLfloat vertices_position[] = {
    x, y,
    x+w, y,
    x+w, y+h,
    x, y+h,
};
glEnableClientState(GL_VERTEX_ARRAY);
glVertexPointer(2, GL_FLOAT, 0, vertices_position);
glDrawArrays(GL_QUADS, 0, 4);
glDisableClientState(GL_VERTEX_ARRAY);

我使用这个发光，我没有得到编译错误，所有我得到的是什么都没有在屏幕上绘制。

如果我用这个代替它就可以了:

glPushMatrix();
    glTranslatef(0, 0, 0);
    glScalef(scale,scale,1);
    //set color
    glColor4f(R, G, B, A);
    glBegin( GL_QUADS );
        glTexCoord2f(  texLeft,    texTop );
        glVertex2f( x, y );
        glTexCoord2f( texRight,    texTop );
        glVertex2f( x+w, y );
        glTexCoord2f( texRight, texBottom );
        glVertex2f( x+w, y+h );
        glTexCoord2f(  texLeft, texBottom );
        glVertex2f( x, y+h );
    glEnd();
glPopMatrix();

我很笨…我指定使用纹理，但从未绑定任何顶点…

下面的代码运行正常:

GLfloat vertices_position[] = {
    x, y,
    x+w, y,
    x+w, y+h,
    x, y+h,
};
GLfloat texture_coord[] = {
    texLeft, texTop,
    texRight, texTop,
    texRight, texBottom,
    texLeft, texBottom,
};
glEnableClientState(GL_VERTEX_ARRAY);
glVertexPointer(2, GL_FLOAT, 0, vertices_position);
glEnableClientState( GL_TEXTURE_COORD_ARRAY );
glTexCoordPointer(2, GL_FLOAT, 0, texture_coord);
glDrawArrays(GL_QUADS, 0, 4);
glDisableClientState( GL_TEXTURE_COORD_ARRAY );
glDisableClientState( GL_VERTEX_ARRAY );

一切正常:

#include <GL/glew.h>
#include <GL/glut.h>
bool vertexArray = false;
void keyboard( unsigned char key, int x, int y )
{
    if( key == 't' ) vertexArray = !vertexArray;
    glutPostRedisplay();
}
void display()
{
    glClear( GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT );
    glMatrixMode( GL_PROJECTION );
    glLoadIdentity();
    double winWidth = glutGet( GLUT_WINDOW_WIDTH );
    double winHeight = glutGet( GLUT_WINDOW_HEIGHT );
    double ar = winWidth / winHeight;
    glOrtho( -1 * ar, 1 * ar, -1, 1, -1, 1);
    glMatrixMode( GL_MODELVIEW );
    glLoadIdentity();
    float x = -0.5f;
    float y = -0.5f;
    float w = 1;
    float h = 1;
    float scale = 1;
    glPushMatrix();
    glTranslatef(0, 0, 0);
    glScalef(scale,scale,1);
    //set color
    glColor4f( 1, 0, 0, 1 );
    if( vertexArray )
    {
        GLfloat vertices_position[] = {
            x, y,
            x+w, y,
            x+w, y+h,
            x, y+h,
        };
        glEnableClientState(GL_VERTEX_ARRAY);
        glVertexPointer(2, GL_FLOAT, 0, vertices_position);
        glDrawArrays(GL_QUADS, 0, 4);
        glDisableClientState(GL_VERTEX_ARRAY);
    }
    else
    {
        glBegin( GL_QUADS );
        glVertex2f( x, y );
        glVertex2f( x+w, y );
        glVertex2f( x+w, y+h );
        glVertex2f( x, y+h );
        glEnd();
    }
    glPopMatrix();
    glutSwapBuffers();
}
int main( int argc, char **argv )
{
    glutInit( &argc, argv );
    glutInitDisplayMode( GLUT_RGBA | GLUT_DEPTH | GLUT_DOUBLE );
    glutInitWindowSize( 640, 480 );
    glutCreateWindow( "GLUT" );
    glutDisplayFunc( display );
    glutKeyboardFunc( keyboard );
    glewInit();
    glutMainLoop();
    return 0;
}
相关文章：