Question

目前,正在形成一个背景,然后将一个透明三角地纳入到底土缓冲地带,然后将三角地推到一个蓝广场。 i 正在研究效果,将是一个蓝广场,具有暴露背景的三角洞。但是,一切照旧都是从其他一切方面抽取的黑三角。 i 认为对广场产生了预期的效果,但与此同时,对地主也适用了。

我的问题是,如何调整以下法典,以便通过广场的三角洞展示背景?

static void Draw(void)
{
glClear(GL_COLOR_BUFFER_BIT | GL_STENCIL_BUFFER_BIT);

//big blue square
glColor3ub(0,255,255);
glBegin(GL_POLYGON);
glVertex3i(5, 5, 0);
glVertex3i(-5, 5, 0);
glVertex3i(-5, -5, 0);
glVertex3i(5, -5, 0);
glEnd();

glStencilFunc(GL_ALWAYS, 1, 1);
glStencilOp(GL_KEEP, GL_KEEP, GL_REPLACE);

/* transparent triangle */
glColor4ub(0.0f, 0.0f, 0.0f, 0.0f);
glBegin(GL_POLYGON);
glVertex3i(-4, -4, 0);
glVertex3i(4, -4, 0);
glVertex3i(0, 4, 0);
glEnd();

glStencilFunc(GL_EQUAL, 1, 1);
glStencilOp(GL_INCR, GL_KEEP, GL_DECR);

glStencilFunc(GL_EQUAL, 2, 1);
glStencilOp(GL_KEEP, GL_KEEP, GL_KEEP);

/* blue square */
glColor3ub(0, 0, 200);
glBegin(GL_POLYGON);
glVertex3i(3, 3, 0);
glVertex3i(-3, 3, 0);
glVertex3i(-3, -3, 0);
glVertex3i(3, -3, 0);
glEnd();

if (doubleBuffer) {
    glutSwapBuffers();
} else {
    glFlush();
}
}

Answer 1

问题一: 如果在先进行可磨损的sten子测试,或将sten功能转至GL_ ALWAYS 以便碎片穿透(I recomment使碎片消失)。之后,你又重新设定了两块不同的天花,但你也不打算这样做。因此,这一改动:

glDisable(GL_STENCIL_TEST);
glStencilMask(0x0);

draw_background();

glEnable(GL_STENCIL_TEST);
glStencilMask(0x1);
glStencilFunc(GL_ALWAYS, 0x1, 0x1);
glStencilOp(GL_KEEP, GL_KEEP, GL_REPLACE);
glColorMask(GL_FALSE, GL_FALSE, GL_FALSE, GL_FALSE);
glDepthMask(GL_FALSE);

draw_trangle();

glStencilFunc(GL_NOTEQUAL, 0x1, 0x1);
glStencilOp(GL_KEEP, GL_KEEP, GL_KEEP);
glColorMask(GL_TRUE, GL_TRUE, GL_TRUE, GL_TRUE);
glDepthMask(GL_TRUE);

draw_blue_square();

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