我在OpenGL中使用GL_POINTS实现了一个简单的粒子效果。下面的代码被调用,按照从相机最远的粒子到相机最近的粒子的顺序传递粒子:
void draw_particle(particle* part) {
/* The following is how the distance is calculated when ordering.
* GLfloat distance = sqrt(pow(get_camera_pos_x() - part->pos_x, 2) + pow(get_camera_pos_y() - part->pos_y, 2) + pow(get_camera_pos_z() - part->pos_z, 2));
*/
static GLfloat quadratic[] = {0.005, 0.01, 1/600.0};
glPointParameterfvARB(GL_POINT_DISTANCE_ATTENUATION_ARB, quadratic);
glPointSize(part->size);
glEnable(GL_BLEND);
glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA);
glEnable(GL_POINT_SPRITE_ARB);
glEnable(GL_TEXTURE_2D);
glBegin(GL_POINTS);
glColor4f(part->r, part->g, part->b, part->a);
glVertex3f(part->pos_x, part->pos_y, part->pos_z);
glEnd();
glDisable(GL_BLEND);
glDisable(GL_POINT_SPRITE_ARB);
}
然而,在渲染时存在一些伪影问题,如下图所示:伪影图像 http://img199.imageshack.us/img199/9574/particleeffect.png 如果我禁用深度测试,则问题会消失,但我需要效果能够与场景中的其他元素交互,根据深度在相同的GL_TRIANGLE_STRIP元素前后出现。