首先，我想提及的是，我在这里找到了我认为完全相同的问题，很遗憾没有答案：
Java Using OpenGL Stencil to create Outline
我将在下面发布我的代码，但首先是问题所在：从这次捕获**中，您可以看到整个框架结构正在显示，而不是围绕球体的单行显示。我想摆脱里面所有这些行！
**显然我无法添加图片：请参见此链接-想象一个球体，其四边形的所有边缘都以3像素大的大线条可见。
http://srbwks36224-03.engin.umich.edu/kdi/images/gs_sphere_with_frame.jpg
这是给出该结果的代码：
// First render the sphere:
// inside "show" is all the code to display a textured sphere
// looking like earth
sphe->show();
// Now get ready for stencil buffer drawing pass:
// 1. Clear and initialize it
// 2. Activate stencil buffer
// 3. On the first rendering pass, we want to "SUCCEED ALWAYS"
// and write a "1" into the stencil buffer accordingly
// 4. We don't need to actually render the object, hence disabling RGB mask
glClearStencil(0); //Edit: swapped this line and below
glClear(GL_STENCIL_BUFFER_BIT);
glEnable(GL_STENCIL_TEST);
glStencilFunc(GL_NEVER, 0x1, 0x1); //Edit: GL_ALWAYS
glStencilOp(GL_REPLACE, GL_KEEP, GL_KEEP); //Edit: GL_KEEP, GL_KEEP, GL_REPLACE
glPolygonMode(GL_FRONT_AND_BACK, GL_FILL);
glColorMask(GL_FALSE, GL_FALSE, GL_FALSE, GL_FALSE);
glDepthMask(GL_FALSE); // As per Andon's comment
sphe->show();
// At this point, I expect to have "1" on the entire
// area covered by the sphere, so...
// 1. Stencil test should fail for anything, but 0 value
// RM: commented is another option that should work too I believe
// 2. The stencil op instruction at the point is somewhat irrelevant
// (if my understanding is correct), because we won't do anything
// else with the stencil buffer after that.
// 3. Re-enable RGB mask, because we want to draw this time
// 4. Switch to LINE drawing instead of FILL and
// 5. set a bigger line width, so it will exceed the model boundaries.
// We do want this, otherwise the line would not show
// 6. Don't mind the "uniform" setting instruction, this is so
// that my shader knows it should draw in plain color
// 7. Draw the sphere's frame
// 8. The principle, as I understand it is that all the lines should
// find themselves matched to a "1" in the stencil buffer and therefore
// be ignored for rendering. Only lines on the edges of the model should
// have half their width not failing the stencil test.
glStencilFunc(GL_EQUAL, 0x0, 0x1);
//glStencilFunc(GL_NOTEQUAL, 0x1, 0x1);
glStencilOp(GL_KEEP, GL_KEEP, GL_REPLACE);
glColorMask(GL_TRUE, GL_TRUE, GL_TRUE, GL_TRUE);
glDepthMask(GL_TRUE);
glLineWidth(3);
glPolygonMode(GL_FRONT_AND_BACK, GL_LINE);
psa::shader::setUniform("outlining", 1);
sphe->show();
psa::shader::setUniform("outlining", 0);
现在只是为了证明一点，我厌倦了使用模版缓冲区做一些不同的事情-我只是想确保代码中的所有内容都正确无误，以便正常工作。
**再次遗憾的是，我无法显示得到的结果的屏幕截图：场景是这样的
http://mathworld.wolfram.com/images/eps-gif/SphereSphereInterGraphic_700.gif
但是较小的球体是不可见的（禁用了RGB蒙版），并且可以通过孔看到世界背景（而不是较大球体的内部-禁用了面剔除）。
这就是代码。有趣的是，我可以更改许多事情，例如激活/停用STENCIL_TEST，到处更改对GL_KEEP的操作，甚至将第二个stencilFunc更改为“ NOT EQUAL 0”……结果总是一样的！我想我在这里缺少一些基本知识。
void testStencil()
{
// 1. Write a 1 in the Stencil buffer for
// every pixels of the first sphere:
// All colors disabled, we don't need to see that sphere
glEnable(GL_STENCIL_TEST);
glStencilFunc(GL_ALWAYS, 0x1, 0x1);
glStencilOp(GL_KEEP, GL_KEEP, GL_REPLACE);
glColorMask(GL_FALSE, GL_FALSE, GL_FALSE, GL_FALSE);
glDepthMask(GL_FALSE); // Edit: added this
{
sphe->W = mat4::trans(psa::vec4(1.0, 1.0, 1.0)) * mat4::scale(0.9);
sphe->show();
}
// 2. Draw the second sphere with the following rule:
// fail the stencil test for every pixels with a 1.
// This means that any pixel from first sphere will
// not be draw as part of the second sphere.
glStencilFunc(GL_EQUAL, 0x0, 0x1);
glStencilOp(GL_KEEP, GL_KEEP, GL_REPLACE);
glColorMask(GL_TRUE, GL_TRUE, GL_TRUE, GL_TRUE);
glDepthMask(GL_TRUE); // Edit: added this
{
sphe->W = mat4::trans(psa::vec4(1.2, 1.2, 1.2)) * mat4::scale(1.1);
sphe->show();
}
}
瞧！如果有人能指出正确的方向，我将不胜感激。我还将确保将您的答案参考我发现的另一篇文章。
最佳答案
此问题中发布的OpenGL代码有效。问题的原因在于窗口初始化/创建：
下面分别是有效的代码的SDL1.2和SDL2版本。请注意，在两种情况下，SetAttribute语句都放置在窗口创建之前。主要的问题是，放错位置的语句不一定会在运行时失败，但也不起作用。
SDL1.2：
if(SDL_Init(SDL_INIT_EVERYTHING) < 0)
{
throw "Video initialization failed";
}
SDL_GL_SetAttribute(SDL_GL_RED_SIZE, 5);
SDL_GL_SetAttribute(SDL_GL_GREEN_SIZE, 5);
SDL_GL_SetAttribute(SDL_GL_BLUE_SIZE, 5);
SDL_GL_SetAttribute(SDL_GL_DEPTH_SIZE, 24);
SDL_GL_SetAttribute(SDL_GL_DOUBLEBUFFER, 1);
SDL_GL_SetAttribute(SDL_GL_STENCIL_SIZE, 8);
SDL_GL_SetAttribute(SDL_GL_MULTISAMPLEBUFFERS, 1);
SDL_GL_SetAttribute(SDL_GL_MULTISAMPLESAMPLES,16);
SDL_GL_SetAttribute(SDL_GL_ACCELERATED_VISUAL, 1);
const SDL_VideoInfo * i;
if((i = SDL_GetVideoInfo()) == NULL)
{
throw "Video query failed";
}
int flag = (fs ? SDL_OPENGL | SDL_FULLSCREEN : SDL_OPENGL);
if(SDL_SetVideoMode(w, h, i->vfmt->BitsPerPixel, flag) == 0)
{
throw "Video mode set failed";
}
glewExperimental = GL_TRUE;
if(glewInit() != GLEW_OK)
{
throw "Could not initialize GLEW";
}
if(!glewIsSupported("GL_VERSION_3_3"))
{
throw "OpenGL 3.3 not supported";
}
SDL2（本质上是相同的代码，只是窗口创建函数会更改）：
if(SDL_Init(SDL_INIT_EVERYTHING) < 0)
{
throw "Video initialization failed";
}
SDL_GL_SetAttribute(SDL_GL_RED_SIZE, 5);
SDL_GL_SetAttribute(SDL_GL_GREEN_SIZE, 5);
SDL_GL_SetAttribute(SDL_GL_BLUE_SIZE, 5);
SDL_GL_SetAttribute(SDL_GL_DEPTH_SIZE, 24);
SDL_GL_SetAttribute(SDL_GL_DOUBLEBUFFER, 1);
SDL_GL_SetAttribute(SDL_GL_STENCIL_SIZE, 8);
SDL_GL_SetAttribute(SDL_GL_MULTISAMPLEBUFFERS, 1);
SDL_GL_SetAttribute(SDL_GL_MULTISAMPLESAMPLES,16);
SDL_GL_SetAttribute(SDL_GL_ACCELERATED_VISUAL, 1);
int flag = SDL_WINDOW_OPENGL;
if((win = SDL_CreateWindow("engine", 100, 100, w, h, flag)) == NULL)
{
throw "Create SDL Window failed";
}
context = SDL_GL_CreateContext(win);
glewExperimental = GL_TRUE;
if(glewInit() != GLEW_OK)
{
throw "Could not initialize GLEW";
}
if(!glewIsSupported("GL_VERSION_3_3"))
{
throw "OpenGL 3.3 not supported";
}
几点值得一提：
1.即使我了解不建议这样做，SDL_GL_SetAttribute（SDL_GL_STENCIL_SIZE，1）也可以工作
2.在SDL2中，对我来说SDL_GL_SetAttribute SDL_GL_MULTISAMPLESAMPLES上升到16，但是在glewInit（）失败后，但是，在窗口创建后移动多重采样设置，突然glewInit停止抱怨：我的猜测是，它只是被忽略了。
3.在SDL1.2中，多重采样“似乎”的任何值都可以工作
4.考虑到模板缓冲功能，下面的代码也只能工作，但是我将其发布基本上是在提出一个问题：实际上有多少个Attribute设置有效？以及如何知道，因为代码可以编译并运行而没有明显的问题？
// PROBABLY WRONG:
// ----
SDL_GL_SetAttribute(SDL_GL_STENCIL_SIZE, 8);
const SDL_VideoInfo * i;
if((i = SDL_GetVideoInfo()) == NULL)
{
throw "Video query failed";
}
int flag = (fs ? SDL_OPENGL | SDL_FULLSCREEN : SDL_OPENGL);
if(SDL_SetVideoMode(w, h, i->vfmt->BitsPerPixel, flag) == 0)
{
throw "Video mode set failed";
}
// No idea if the below is actually applied!
SDL_GL_SetAttribute(SDL_GL_RED_SIZE, 5);
SDL_GL_SetAttribute(SDL_GL_GREEN_SIZE, 5);
SDL_GL_SetAttribute(SDL_GL_BLUE_SIZE, 5);
SDL_GL_SetAttribute(SDL_GL_DEPTH_SIZE, 24);
SDL_GL_SetAttribute(SDL_GL_DOUBLEBUFFER, 1);
SDL_GL_SetAttribute(SDL_GL_MULTISAMPLEBUFFERS, 1);
SDL_GL_SetAttribute(SDL_GL_MULTISAMPLESAMPLES, 16);
SDL_GL_SetAttribute(SDL_GL_ACCELERATED_VISUAL, 1);