问题描述
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我正在使用glColor3f()和GL_QUAD_STRIP绘制彼此相邻的2个正方形,但是看来它们正在使2个正方形之间的颜色逐渐褪色,有什么办法可以防止这种情况发生?还是GL_QUAD_STRIP根本不适合这种事情? GL_QUADS更合适,但这太容易了。
glBegin(GL_QUAD_STRIP);
glColor3f(1.0f,1.0f,1.0f);
glVertex3f(0.0f,0.0f,0.0f);
glVertex3f(0.0f,0.0f);
glVertex3f(1.0f,0.0f);
glColor3f(0.0f,0.0f);
glVertex3f(2.0f,0.0f);
glColor3f(1.0f,1.0f);
glEnd();
解决方法
通常,颜色附加到每个顶点,而不是每个四边形。因此,由于在条带的2个四边形之间共享2个顶点,因此您将获得用于这两个颜色的颜色(以及您正在观察的“褪色”颜色。这称为插值)。
现在,在您的特定情况下,可以使用一种OpenGL模式来帮助您:您可以告诉OpenGL根本不对颜色进行插值,而只获取完整图元的每个图元的最后一个顶点(这里为四边形)的颜色。
通过以下状态完成此操作:
glShadeModel(GL_FLAT);
,每次进行glColor3f调用时,它将将该颜色与每个顶点相关联,直到您使用不同的颜色进行不同的glColor3f调用。我将使用GL_QUADS并将其分解为两个独立的四边形,如下所示(我相信是顺时针方向):
glBegin(GL_QUADS);
glColor3f(1.0f,1.0f,1.0f);
glVertex3f(0.0f,0.0f,0.0f);
glVertex3f(0.0f,0.0f);
glVertex3f(1.0f,0.0f);
glColor3f(0.0f,0.0f);
glVertex3f(2.0f,0.0f);
glEnd();