How to use the template buffer in FBO

Document directory

• Common FBO frameworks
• How to add stencel buffer in FBO
• Use stencel buffer correctly in FBO
• Reference

FBO common frameworks generally only require color buffer and depth buffer. The former generally uses textures, and the latter generally uses RBO. The standard procedure is as follows:

// Create // frame buffer objectglgenframebuffers (1, & fboid); glbindframebuffer (gl_framebuffer, fboid); // color buffer with texture objectglgentextures (1, & color_rboid); glbindtexture (callback, callback, color_rboid); glteximage2d (latency, 0, gl_rgba, targetwidth, targetheight, 0, gl_rgba, latency, 0); gltexparameterf (latency, latency, gl_nearest); gltexparameterf (gl_texture_2d, Response, gl_linear); gltexparameterf (response, response, gl_repeat); gltexparameterf (response, response, gl_repeat); // depth buffer with render buffer objectglgenrenderbuffers (1, & response ); glbindrenderbuffer (gl_renderbuffer, depth_rboid); glrenderbufferstorage (gl_renderbuffer, gl_depth_component24, targetwidth, targetheight); // attach color buffer to FBO Struct (gl_framebuffer, struct, gl_texture_2d, color_rboid, 0); // attach depth buffer to terminate (gl_framebuffer, callback, gl_renderbuffer, callback); // also attach as a struct (gl_framebuffer, gl_stencil_attachment, gl_renderbuffer, depth_stencil_rb); // Delete if (fboid! = 0) {gldeleteframebuffers (1, & fboid); fboid = 0;} If (depth_rboid! = 0) {gldeleterenderbuffers (1, & depth_rboid); depth_rboid = 0;} If (color_rboid) {average (1, & color_rboid); color_rboid = 0 ;}

In FBO, how to add stencel buffer to normal people will think that stencel buffer is similar to depth buffer, and thus write a framework similar to depth buffer:

// Create stencel buffer in the form of RBO glgenrenderbuffers (1, & cached); glbindrenderbuffer (gl_renderbuffer, buffers); glrenderbufferstorage (gl_renderbuffer, gl_stencil_index, targetwidth, targetheight ); // associate stencel buffer with fboglframebufferrenderbuffer (gl_framebuffer, latency, gl_renderbuffer, stencil_rboid); // Delete stencel buffergldeleterenderbuffers (1, & stencil_rboid );

However, in actual tests, it is found that stencel buffer does not work at all. The following is a test function:

void stencilRenderTest(){GLdouble dRadius = 0.1; // Initial radius of spiralGLdouble dAngle;        // Looping variablefloat x = 100;float y = 100;float rsize = 25;// Clear blue windowglClearColor(0.0f, 0.0f, 1.0f, 0.0f);// Use 0 for clear stencil, enable stencil testglClearStencil(0.0f);glEnable(GL_STENCIL_TEST);// Clear color and stencil bufferglClear(GL_COLOR_BUFFER_BIT | GL_STENCIL_BUFFER_BIT);// All drawing commands fail the stencil test, and are not// drawn, but increment the value in the stencil buffer. glStencilFunc(GL_NEVER, 0x0, 0x0);glStencilOp(GL_INCR, GL_INCR, GL_INCR);// Spiral pattern will create stencil pattern// Draw the spiral pattern with white lines. We // make the lines  white to demonstrate that the // stencil function prevents them from being drawnglColor3f(1.0f, 1.0f, 1.0f);glBegin(GL_LINE_STRIP);for(dAngle = 0; dAngle < 400.0; dAngle += 0.1){glVertex2d(dRadius * cos(dAngle), dRadius * sin(dAngle));dRadius *= 1.002;}glEnd();// Now, allow drawing, except where the stencil pattern is 0x1// and do not make any further changes to the stencil bufferglStencilFunc(GL_NOTEQUAL, 0x1, 0x1);glStencilOp(GL_KEEP, GL_KEEP, GL_KEEP);// Now draw red bouncing square// (x and y) are modified by a timer functionglColor3f(1.0f, 0.0f, 0.0f);glRectf(x, y, x + rsize, y - rsize);}

When stenpencil is correct, the result shows a blue background, a small red rectangle, and an arc inside the rectangle, right.

The incorrect result is the concentric ring of the blue background and the red block of a rectangle. In FBO, use stencel buffer correctly. In the official wiki tutorial, find the answer:

Ever ever make a stencel buffer. all GPUs and all drivers do not support an independent stencel buffer. if you need a stencel buffer, then you need to make a depth = 24, stencel = 8 buffer, also called d24s8. please search for the example about gl_ext_packed_depth_stencer
On this page.
Never create a single template buffer. All GPUs and drivers do not support separate template buffers. If you need to create a template buffer in depth and share a buffer with the template, the format is depth_24_stencil_8.

The Code is as follows:

// Create // frame buffer objectglgenframebuffers (1, & fboid); glbindframebuffer (gl_framebuffer, fboid); // color buffer with texture objectglgentextures (1, & color_rboid); glbindtexture (callback, callback, color_rboid); glteximage2d (latency, 0, gl_rgba, targetwidth, targetheight, 0, gl_rgba, latency, 0); gltexparameterf (latency, latency, gl_nearest); gltexparameterf (gl_texture_2d, Response, gl_linear); gltexparameterf (gl_texture_2d, response, gl_repeat); gltexparameterf (response, response, gl_repeat); // depth buffer and stenpencil terminate (1, & response ); glbindrenderbuffer (gl_renderbuffer, depth_stencil_rb); glrenderbufferstorage (gl_renderbuffer, gl_depth24_stencil8, targetwidth, targetheight); // not gl_depth_component2 4 but buffers // attach color buffer to encode (gl_framebuffer, gl_color_attachment0, gl_texture_2d, color_rboid, 0); // attach depth buffer to encode (gl_framebuffer, callback, gl_renderbuffer, callback ); // also attach as a stencilglframebufferrenderbuffer (gl_framebuffer, gl_stencil_attachment, gl_renderbuffer, depth_stencil_rb );// Delete if (fboid! = 0) {gldeleteframebuffers (1, & fboid); fboid = 0;} If (depth_stencil_rb! = 0) {gldeleterenderbuffers (1, & depth_stencil_rb); Limit = 0;} If (color_rboid) {gldeletextures (1, & color_rboid); color_rboid = 0 ;}

Reference

OpenGL official wiki: https://www.opengl.org/wiki/Framebuffer_Object_Examples

History:

1. Correct FBO frame buffer creation bug on February 14,. the renderbuffer format should be gl_depth24_stencil8 instead of gl_depth_component24.